Open Versus Closed Hearing-Aid Fittings: A Literature Review of Both Fitting Approaches
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paper_title: Occlusion effect of earmolds with different venting systems.

paper_content:

In this study the occlusion effect was quantified for five types of earmolds with different venting. Nine normal-hearing listeners and ten experienced hearing aid users were provided with conventional earmolds with 1.6 and 2.4 mm circular venting, shell type earmolds with a novel vent design with equivalent crosssectional vent areas, and nonoccluding soft silicone eartips of a commercial hearing instrument. For all venting systems, the occlusion effect was measured using a probe microphone system and subjectively rated in test and retest sessions. The results for both normal-hearing subjects and hearing aid users showed that the novel vents caused significantly less occlusion than the traditional vents. Occlusion effect associated with the soft silicone eartip was comparable to the nonoccluded ear. Test-retest reproducibility was higher for the subjective occlusion rating than for the objectively measured occlusion. Perceived occlusion revealed a closer relationship to measured occlusion in the ear in which the measured occlusion effect was higher (“high OE” ear) than in the “low OE” ear. As our results suggest that subjective judgment of occlusion is directly related to the acoustic mass of the air column in the vent, the amount of perceived occlusion may be predicted by the vent dimensions.
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paper_title: Acoustic Attenuation between the Ears

paper_content:

In an investigation of the acoustical insulation between the ears, various earphones and obturating devices were used. Bone conduction was shown to be chiefly responsible for the acoustical leakage between the ears. Conditions were determined under which interaural insulation could be increased considerably. Most of the measurements were performed with a compensation method which appears to give more precise results than methods previously used, and which permits phase measurements.
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paper_title: A Multicenter Trial of an Assess-and-Fit Hearing Aid Service Using Open Canal Fittings and Comply Ear Tips

paper_content:

Large potential benefits have been suggested for an assess-and-fit approach to hearing health care, particularly using open canal fittings. However, the clinical effectiveness has not previously been evaluated, nor has the efficiency of this approach in a National Health Service setting. These two outcomes were measured in a variety of clinical settings in the United Kingdom. Twelve services in England and Wales participated, and 540 people with hearing problems, not previously referred for assessment, were included. Of these, 68% (n = 369) were suitable and had hearing aids fitted to NAL NL1 during the assess-and-fit visit using either open ear tips, or Comply ear tips. The Glasgow Hearing Aid Benefit Profile was used to compare patients fitted with open ear tips with a group of patients from the English Modernization of Hearing Aid Services evaluation, who used custom earmolds. This showed a significant improvement in outcome for those with open ear tips after allowing for age and hearing loss in the analysis. In particular, the benefits of using bilateral open ear tips were significantly larger than bilateral custom ear-molds. This assess-and-fit model showed a mean service efficiency gain of about 5% to 10%. The actual gain will depend on current practice, in particular on the separate appointments used, the numbers of patients failing to attend appointments, and the numbers not accepting a hearing aid solution for their problem. There are potentially further efficiency and quality gains to be made if patients are appropriately triaged before referral.
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paper_title: Preferred signal path delay and high-pass cut-off in open fittings

paper_content:

AbstractThe combination of delayed sound from a digital hearing aid with direct sound through an open or vented fitting can potentially degrade the sound quality due to audible changes in timbre and/or perception of echo. The present study was designed to test a number of delay and high-pass combinations under worst-case (i.e. most sensitive) conditions. Eighteen normal-hearing and 18 mildly hearing-impaired subjects performed the test in a paired comparison (A/B) task. The subjects were asked to select a preferred setting with respect to sound quality. The test was set in an anechoic chamber using recorded speech, environmental sounds, and own voice. Experimental hearing aids were fitted binaurally with open domes thus providing maximum ventilation. The preference data were processed using a statistical choice model that derives a ratio-scale. The analysis indicated that in these test conditions there was no change in sound quality when varying the delay in the range 5–10 ms and that there was a preferen...
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paper_title: Comparison of Vent Effects between a Solid Earmold and a Hollow Earmold

paper_content:

where the thickness of the shell was the length of the vent. Vent diameters were 0, 1, 2, and 3 mm. Data Collection and Analysis: The vent effect was evaluated on real-ear aided response, real-ear occluded response during vocalization, subjective occlusion rating, insertion loss, and maximum available gain before feedback. Real-ear measurements were made with the Fonix 6500 probemicrophone real-ear system. Vocalizations from the participants were analyzed with a custom MATLAB program, and statistical analysis was conducted with SPSS software. Results: A systematic vent effect was seen with each earmold type as the nominal vent diameter changed. For the same vent diameter, the vent effect seen with the hollow earmold was greater than that of the solid earmold. Conclusions: Because of the difference in vent length (and thus acoustic mass) between a solid and a hollow earmold, the effect of vent diameter in a hollow earmold is more pronounced than that seen in a solid earmold of the same nominal vent diameter. Thus, a smaller vent diameter will be needed in a hollow earmold than in a solid earmold to achieve similar vent effects.
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paper_title: Own voice qualities (OVQ) in hearing-aid users: There is more than just occlusion

paper_content:

AbstractObjective: Hearing-aid users’ problems with their own voice caused by occlusion are well known. Conversely, it remains essentially undocumented whether hearing-aid users expected not to have occlusion-related problems experience own-voice issues. Design: To investigate this topic, a dedicated Own Voice Qualities (OVQ) questionnaire was developed and used in two experiments with stratified samples. Study sample: In the main experiment, the OVQ was administered to 169 hearing-aid users (most of whom were expected not to have occlusion-related problems) and to a control group of 56 normally-hearing people. In the follow-up experiment, the OVQ was used in a cross-over study where 43 hearing-aid users rated own voice for an open fitting and a small-vent earmould fitting. Results: The results from the main experiment show that hearing-aid users (without occlusion) have more problems than the normal-hearing controls on several dimensions of own voice. The magnitude of these differences was found to be ge...
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paper_title: Comparison of Vent Effects between a Solid Earmold and a Hollow Earmold

paper_content:

where the thickness of the shell was the length of the vent. Vent diameters were 0, 1, 2, and 3 mm. Data Collection and Analysis: The vent effect was evaluated on real-ear aided response, real-ear occluded response during vocalization, subjective occlusion rating, insertion loss, and maximum available gain before feedback. Real-ear measurements were made with the Fonix 6500 probemicrophone real-ear system. Vocalizations from the participants were analyzed with a custom MATLAB program, and statistical analysis was conducted with SPSS software. Results: A systematic vent effect was seen with each earmold type as the nominal vent diameter changed. For the same vent diameter, the vent effect seen with the hollow earmold was greater than that of the solid earmold. Conclusions: Because of the difference in vent length (and thus acoustic mass) between a solid and a hollow earmold, the effect of vent diameter in a hollow earmold is more pronounced than that seen in a solid earmold of the same nominal vent diameter. Thus, a smaller vent diameter will be needed in a hollow earmold than in a solid earmold to achieve similar vent effects.
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paper_title: The Occlusion Effect in Unilateral versus Bilateral Hearing Aids

paper_content:

The benefit of bilateral hearing aids is well documented, but many hearing-aid users still wear only one aid. It is plausible that the occlusion effect is part of the reason for some hearing-aid users not wearing both hearing aids. In this study we quantified the subjective occlusion effect by asking ten experienced users of bilateral hearing aids and a reference group of ten normal-hearing individuals to rate the naturalness of their own voice while reading a text sample aloud. The subjective occlusion effect was evaluated in the unilateral versus bilateral condition for a variety of vent designs in earmolds and in a custom hearing aid. The subjective occlusion effect was significantly higher for bilateral hearing aids with all vent designs with the exception of a non-occluding eartip option. The subjective occlusion effect was reduced with the more open vent designs in both the unilateral and bilateral conditions. Assuming that the occlusion effect is a barrier to bilateral hearing aid use, these results indicate that open-hearing-aid fittings can help promote the use of two aids.
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paper_title: Vent configurations on subjective and objective occlusion effect.

paper_content:

The current study reexamined the effect of vent diameters on objective and subjective occlusion effect (OE) while minimizing two possible sources of variability. Nine hearing-impaired participants with primarily a high-frequency hearing loss were evaluated. Laser shell-making technology was used to make ear inserts of completely-in-the-canal (CIC) hearing aids for the study. This was to minimize any potential slit leakage from the inserts. The vent dimensions were systematically altered during the study. Participants sustained /i/ for 5 sec, and the real-ear occluded response was measured with a custommade program that performed frequency averaging to reduce response variability. Participants also repeated the phrase “Baby Jeannie is teeny tiny” and rated their own voice. The results showed a systematic change in the objective OE and subjective ratings of OE as the vent diameter was modified. Furthermore, a significant correlation was seen between subjective rating and objective occlusion effect.
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paper_title: Relative loudness perception of low and high frequency sounds in the open and occluded ear

paper_content:

A comparison of published equal loudness contours indicates that different shapes are obtained at a comfortable level when the measurements are done in an occluded ear than when they are done in an open ear, even though all measurements are expressed as dB SPL at the eardrum. This paper presents the result from a loudness balancing test which confirms this observation. Eleven normal-hearing listeners balanced the level of a 500- and a 3000-Hz octave band babble-noise to the level of a 1500-Hz octave band babble-noise. The balancing test was completed in open and occluded ears using a loudspeaker and a hearing aid receiver, respectively. A probe tube microphone was used to measure the actual levels presented near the individual’s eardrum. The results show that an average of 10 dB higher level was selected for the 500-Hz octave band when listening with the occluded ear than when listening with the open ear. A large range of factors is discussed, but no physical explanation for the discrepancy was found. The...
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paper_title: Occlusion effect of earmolds with different venting systems.

paper_content:

In this study the occlusion effect was quantified for five types of earmolds with different venting. Nine normal-hearing listeners and ten experienced hearing aid users were provided with conventional earmolds with 1.6 and 2.4 mm circular venting, shell type earmolds with a novel vent design with equivalent crosssectional vent areas, and nonoccluding soft silicone eartips of a commercial hearing instrument. For all venting systems, the occlusion effect was measured using a probe microphone system and subjectively rated in test and retest sessions. The results for both normal-hearing subjects and hearing aid users showed that the novel vents caused significantly less occlusion than the traditional vents. Occlusion effect associated with the soft silicone eartip was comparable to the nonoccluded ear. Test-retest reproducibility was higher for the subjective occlusion rating than for the objectively measured occlusion. Perceived occlusion revealed a closer relationship to measured occlusion in the ear in which the measured occlusion effect was higher (“high OE” ear) than in the “low OE” ear. As our results suggest that subjective judgment of occlusion is directly related to the acoustic mass of the air column in the vent, the amount of perceived occlusion may be predicted by the vent dimensions.
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paper_title: Comparison of Vent Effects between a Solid Earmold and a Hollow Earmold

paper_content:

where the thickness of the shell was the length of the vent. Vent diameters were 0, 1, 2, and 3 mm. Data Collection and Analysis: The vent effect was evaluated on real-ear aided response, real-ear occluded response during vocalization, subjective occlusion rating, insertion loss, and maximum available gain before feedback. Real-ear measurements were made with the Fonix 6500 probemicrophone real-ear system. Vocalizations from the participants were analyzed with a custom MATLAB program, and statistical analysis was conducted with SPSS software. Results: A systematic vent effect was seen with each earmold type as the nominal vent diameter changed. For the same vent diameter, the vent effect seen with the hollow earmold was greater than that of the solid earmold. Conclusions: Because of the difference in vent length (and thus acoustic mass) between a solid and a hollow earmold, the effect of vent diameter in a hollow earmold is more pronounced than that seen in a solid earmold of the same nominal vent diameter. Thus, a smaller vent diameter will be needed in a hollow earmold than in a solid earmold to achieve similar vent effects.
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paper_title: The Occlusion Effect in Unilateral versus Bilateral Hearing Aids

paper_content:

The benefit of bilateral hearing aids is well documented, but many hearing-aid users still wear only one aid. It is plausible that the occlusion effect is part of the reason for some hearing-aid users not wearing both hearing aids. In this study we quantified the subjective occlusion effect by asking ten experienced users of bilateral hearing aids and a reference group of ten normal-hearing individuals to rate the naturalness of their own voice while reading a text sample aloud. The subjective occlusion effect was evaluated in the unilateral versus bilateral condition for a variety of vent designs in earmolds and in a custom hearing aid. The subjective occlusion effect was significantly higher for bilateral hearing aids with all vent designs with the exception of a non-occluding eartip option. The subjective occlusion effect was reduced with the more open vent designs in both the unilateral and bilateral conditions. Assuming that the occlusion effect is a barrier to bilateral hearing aid use, these results indicate that open-hearing-aid fittings can help promote the use of two aids.
---
paper_title: Vent configurations on subjective and objective occlusion effect.

paper_content:

The current study reexamined the effect of vent diameters on objective and subjective occlusion effect (OE) while minimizing two possible sources of variability. Nine hearing-impaired participants with primarily a high-frequency hearing loss were evaluated. Laser shell-making technology was used to make ear inserts of completely-in-the-canal (CIC) hearing aids for the study. This was to minimize any potential slit leakage from the inserts. The vent dimensions were systematically altered during the study. Participants sustained /i/ for 5 sec, and the real-ear occluded response was measured with a custommade program that performed frequency averaging to reduce response variability. Participants also repeated the phrase “Baby Jeannie is teeny tiny” and rated their own voice. The results showed a systematic change in the objective OE and subjective ratings of OE as the vent diameter was modified. Furthermore, a significant correlation was seen between subjective rating and objective occlusion effect.
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paper_title: Occlusion effect of earmolds with different venting systems.

paper_content:

In this study the occlusion effect was quantified for five types of earmolds with different venting. Nine normal-hearing listeners and ten experienced hearing aid users were provided with conventional earmolds with 1.6 and 2.4 mm circular venting, shell type earmolds with a novel vent design with equivalent crosssectional vent areas, and nonoccluding soft silicone eartips of a commercial hearing instrument. For all venting systems, the occlusion effect was measured using a probe microphone system and subjectively rated in test and retest sessions. The results for both normal-hearing subjects and hearing aid users showed that the novel vents caused significantly less occlusion than the traditional vents. Occlusion effect associated with the soft silicone eartip was comparable to the nonoccluded ear. Test-retest reproducibility was higher for the subjective occlusion rating than for the objectively measured occlusion. Perceived occlusion revealed a closer relationship to measured occlusion in the ear in which the measured occlusion effect was higher (“high OE” ear) than in the “low OE” ear. As our results suggest that subjective judgment of occlusion is directly related to the acoustic mass of the air column in the vent, the amount of perceived occlusion may be predicted by the vent dimensions.
---
paper_title: The Occlusion Effect in Unilateral versus Bilateral Hearing Aids

paper_content:

The benefit of bilateral hearing aids is well documented, but many hearing-aid users still wear only one aid. It is plausible that the occlusion effect is part of the reason for some hearing-aid users not wearing both hearing aids. In this study we quantified the subjective occlusion effect by asking ten experienced users of bilateral hearing aids and a reference group of ten normal-hearing individuals to rate the naturalness of their own voice while reading a text sample aloud. The subjective occlusion effect was evaluated in the unilateral versus bilateral condition for a variety of vent designs in earmolds and in a custom hearing aid. The subjective occlusion effect was significantly higher for bilateral hearing aids with all vent designs with the exception of a non-occluding eartip option. The subjective occlusion effect was reduced with the more open vent designs in both the unilateral and bilateral conditions. Assuming that the occlusion effect is a barrier to bilateral hearing aid use, these results indicate that open-hearing-aid fittings can help promote the use of two aids.
---
paper_title: Occlusion effect of earmolds with different venting systems.

paper_content:

In this study the occlusion effect was quantified for five types of earmolds with different venting. Nine normal-hearing listeners and ten experienced hearing aid users were provided with conventional earmolds with 1.6 and 2.4 mm circular venting, shell type earmolds with a novel vent design with equivalent crosssectional vent areas, and nonoccluding soft silicone eartips of a commercial hearing instrument. For all venting systems, the occlusion effect was measured using a probe microphone system and subjectively rated in test and retest sessions. The results for both normal-hearing subjects and hearing aid users showed that the novel vents caused significantly less occlusion than the traditional vents. Occlusion effect associated with the soft silicone eartip was comparable to the nonoccluded ear. Test-retest reproducibility was higher for the subjective occlusion rating than for the objectively measured occlusion. Perceived occlusion revealed a closer relationship to measured occlusion in the ear in which the measured occlusion effect was higher (“high OE” ear) than in the “low OE” ear. As our results suggest that subjective judgment of occlusion is directly related to the acoustic mass of the air column in the vent, the amount of perceived occlusion may be predicted by the vent dimensions.
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paper_title: Hearing aids with external receivers: Can they offer power and cosmetics?

paper_content:

The design of hearing solutions for people with moderate to severe hearing loss (HL) traditionally encounters the tradeoff between form and function, appearance and performance. That is, patients typically must sacrifice cosmetics and/or ease of use to obtain devices that can provide them with adequate gain and output. Conversely, larger hearing aid (HA) styles may provide sufficient gain, yet reduce patient satisfaction along a number of other variables. In fact, compared with patients with milder losses, persons with moderate to severe sensorineural HL are less satisfied with their hearing aids along a number of dimensions, 1 including:
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paper_title: Effect of low-frequency gain and venting effects on the benefit derived from directionality and noise reduction in hearing aids

paper_content:

When the frequency range over which vent-transmitted sound dominates amplification increases, the potential benefit from directional microphones and noise reduction decreases. Fitted with clinically appropriate vent sizes, 23 aided listeners with varying low-frequency hearing thresholds evaluated six schemes comprising three levels of gain at 250 Hz (0, 6, and 12 dB) combined with two features (directional microphone and noise reduction) enabled or disabled in the field. The low-frequency gain was 0 dB for vent-dominated sound, while the higher gains were achieved by amplifier-dominated sounds. A majority of listeners preferred 0-dB gain at 250 Hz and the features enabled. While the amount of low-frequency gain had no significant effect on speech recognition in noise or horizontal localization, speech recognition and front/back discrimination were significantly improved when the features were enabled, even when vent-transmitted sound dominated the low frequencies. The clinical implication is that there is...
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paper_title: The Accuracy of Matching Target Insertion Gains With Open-Fit Hearing Aids

paper_content:

Purpose To assess the accuracy with which target insertion gains were matched for a single type of open-fit hearing aid, both on initial fitting and after adjustment. Method The hearing aids were f...
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paper_title: NAL-NL1 procedure for fitting nonlinear hearing aids: characteristics and comparisons with other procedures.

paper_content:

A new procedure for fitting nonlinear hearing aids (National Acoustic Laboratories' nonlinear fitting procedure, version 1 [NAL-NL1]) is described . The rationale is to maximize speech intelligibility while constraining loudness to be normal or less. Speech intelligibility is predicted by the Speech Intelligibility Index (SII), which has been modified to account for the reduction in performance associated with increasing degrees of hearing loss, especially at high frequencies . Prescriptions are compared for the NAL-NL1, desired sensation level [input/output], FIG6, and a threshold version of the Independent Hearing Aid Fitting Forum procedures . For an average speech input level, the NAL-NL1 prescriptions are very similar to those of the well-established NAL-Revised, Profound procedure . Compared with the other procedures, NAL-NL1 prescribes less low-frequency gain for flat and upward sloping audiograms . It prescribes less high-frequency gain for steeply sloping high-frequency hearing losses. NAL-NL1 tends to prescribe less compression than the other procedures . All procedures differ considerably from one another for some audiograms .
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paper_title: Own voice qualities (OVQ) in hearing-aid users: There is more than just occlusion

paper_content:

AbstractObjective: Hearing-aid users’ problems with their own voice caused by occlusion are well known. Conversely, it remains essentially undocumented whether hearing-aid users expected not to have occlusion-related problems experience own-voice issues. Design: To investigate this topic, a dedicated Own Voice Qualities (OVQ) questionnaire was developed and used in two experiments with stratified samples. Study sample: In the main experiment, the OVQ was administered to 169 hearing-aid users (most of whom were expected not to have occlusion-related problems) and to a control group of 56 normally-hearing people. In the follow-up experiment, the OVQ was used in a cross-over study where 43 hearing-aid users rated own voice for an open fitting and a small-vent earmould fitting. Results: The results from the main experiment show that hearing-aid users (without occlusion) have more problems than the normal-hearing controls on several dimensions of own voice. The magnitude of these differences was found to be ge...
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paper_title: The International Outcome Inventory for Hearing Aids (IOI-HA): psychometric properties of the English version.

paper_content:

The International Outcome Inventory for Hearing Aids (IOI-HA) is a seven-item questionnaire designed to be generally applicable in evaluating the effectiveness of hearing aid treatments. The inventory was developed to facilitate cooperation among researchers and program evaluators in diverse settings. It is brief and general enough to be appended to other outcome measures that might be planned in a particular application, and will provide directly comparable data across otherwise incompatible projects. For this plan to be successful, it is essential to generate psychometrically equivalent translations in the languages in which hearing aid research and treatment assessments are performed. This article reports the psychometric properties of the inventory for the original English version. The items are reasonably internally consistent, providing adequate statistical support for summing the scores to generate a total outcome score. However, for maximum internal consistcncy, it would be desirable to generate t...
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paper_title: The abbreviated profile of hearing aid benefit.

paper_content:

OBJECTIVE ::: To develop and evaluate a shortened version of the Profile of Hearing Aid Benefit, to be called the Abbreviated Profile of Hearing Aid Benefit, or APHAB. ::: ::: ::: DESIGN ::: The Profile of Hearing Aid Benefit (PHAB) is a 66-item self-assessment, disability-based inventory that can be used to document the outcome of a hearing aid fitting, to compare several fittings, or to evaluate the same fitting over time. Data from 128 completed PHABs were used to select items for the Abbreviated PHAB. All subjects were elderly hearing-impaired who wore conventional analog hearing aids. Statistics of score distributions and psychometric properties of each of the APHAB subscales were determined. Data from 27 similar subjects were used to examine the test-retest properties of the instrument. Finally, equal-percentile profiles were generated for unaided, aided and benefit scores obtained from successful wearers of linear hearing aids. ::: ::: ::: RESULTS ::: The APHAB uses a subset of 24 of the 66 items from the PHAB, scored in four 6-item subscales. Three of the subscales, Ease of Communication, Reverberation, and Background Noise address speech understanding in various everyday environments. The fourth subscale, Aversiveness of Sounds, quantifies negative reactions to environmental sounds. The APHAB typically requires 10 minutes or less to complete, and it produces scores for unaided and aided performance as well as hearing aid benefit. Test-retest correlation coefficients were found to be moderate to high and similar to those reported in the literature for other scales of similar content and length. Critical differences for each subscale taken individually were judged to be fairly large, however, smaller differences between two tests from the same individual can be significant if the three speech communication subscales are considered jointly. ::: ::: ::: CONCLUSIONS ::: The APHAB is a potentially valuable clinical instrument. It can be useful for quantifying the disability associated with a hearing loss and the reduction of disability that is achieved with a hearing aid.
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paper_title: The Occlusion Effect in Unilateral versus Bilateral Hearing Aids

paper_content:

The benefit of bilateral hearing aids is well documented, but many hearing-aid users still wear only one aid. It is plausible that the occlusion effect is part of the reason for some hearing-aid users not wearing both hearing aids. In this study we quantified the subjective occlusion effect by asking ten experienced users of bilateral hearing aids and a reference group of ten normal-hearing individuals to rate the naturalness of their own voice while reading a text sample aloud. The subjective occlusion effect was evaluated in the unilateral versus bilateral condition for a variety of vent designs in earmolds and in a custom hearing aid. The subjective occlusion effect was significantly higher for bilateral hearing aids with all vent designs with the exception of a non-occluding eartip option. The subjective occlusion effect was reduced with the more open vent designs in both the unilateral and bilateral conditions. Assuming that the occlusion effect is a barrier to bilateral hearing aid use, these results indicate that open-hearing-aid fittings can help promote the use of two aids.
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paper_title: Measuring Satisfaction with Amplification in Daily Life: The SADL Scale

paper_content:

ObjectiveTo develop a self-report inventory to quantify satisfaction with hearing aids.DesignThe inventory was developed in several stages. To determine the elements that are most important to satisfaction for most people, we conducted structured interviews and then designed a questionnaire. Hearing
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paper_title: Occlusion effect of earmolds with different venting systems.

paper_content:

In this study the occlusion effect was quantified for five types of earmolds with different venting. Nine normal-hearing listeners and ten experienced hearing aid users were provided with conventional earmolds with 1.6 and 2.4 mm circular venting, shell type earmolds with a novel vent design with equivalent crosssectional vent areas, and nonoccluding soft silicone eartips of a commercial hearing instrument. For all venting systems, the occlusion effect was measured using a probe microphone system and subjectively rated in test and retest sessions. The results for both normal-hearing subjects and hearing aid users showed that the novel vents caused significantly less occlusion than the traditional vents. Occlusion effect associated with the soft silicone eartip was comparable to the nonoccluded ear. Test-retest reproducibility was higher for the subjective occlusion rating than for the objectively measured occlusion. Perceived occlusion revealed a closer relationship to measured occlusion in the ear in which the measured occlusion effect was higher (“high OE” ear) than in the “low OE” ear. As our results suggest that subjective judgment of occlusion is directly related to the acoustic mass of the air column in the vent, the amount of perceived occlusion may be predicted by the vent dimensions.
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paper_title: Effects of earmold type on ability to locate sounds when wearing hearing aids.

paper_content:

Objective:To determine whether the choice of earmold type can affect aided auditory localization. Hypotheses: 1) for sensorineural hearing losses with good low-frequency hearing (Low group, n = 10), the use of open earmolds could avoid decrements in horizontal plane localization found with closed (o
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paper_title: Effect of low-frequency gain and venting effects on the benefit derived from directionality and noise reduction in hearing aids

paper_content:

When the frequency range over which vent-transmitted sound dominates amplification increases, the potential benefit from directional microphones and noise reduction decreases. Fitted with clinically appropriate vent sizes, 23 aided listeners with varying low-frequency hearing thresholds evaluated six schemes comprising three levels of gain at 250 Hz (0, 6, and 12 dB) combined with two features (directional microphone and noise reduction) enabled or disabled in the field. The low-frequency gain was 0 dB for vent-dominated sound, while the higher gains were achieved by amplifier-dominated sounds. A majority of listeners preferred 0-dB gain at 250 Hz and the features enabled. While the amount of low-frequency gain had no significant effect on speech recognition in noise or horizontal localization, speech recognition and front/back discrimination were significantly improved when the features were enabled, even when vent-transmitted sound dominated the low frequencies. The clinical implication is that there is...
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paper_title: The national acoustic laboratories (NAL) new procedure for selecting the gain and frequency response of a hearing aid

paper_content:

ABSTRACT A new procedure is presented for selecting the gain and frequency response of a hearing aid from pure-tone thresholds. This was developed from research which showed that a previous procedure did not meet its aim of amplifying all frequency bands of speech to equal loudness but that frequency responses which did so were considerably more effective. Measurements of 30 sensorineurally hearing-impaired ears (27 subjects), together with data from other studies, were analyzed to determine the best formula for predicting the optimal frequency response, for each individual, from the audiogram. The analysis indicated that a flat audiogram would require a rising frequency response characteristic of about 8 dB/octave up to 1.25 kHz and thereafter a falling characteristic of about 2 dB/octave. Variations in audiogram slope required about one-third as much variation in response slope. Three frequency average (3FA) gain was calculated to equal the 3FA gain of the previous procedure. Forty-four subjects (67 aided ears) fitted by the new procedure were evaluated by paired comparison judgments of the intelligibility and pleasantness of speech. The prescribed frequency response was seldom inferior to, and usually better than, any of several variations having more, or less, low and/or high-frequency amplification. On the average, used gain was approximately equal to prescribed gain. It is concluded that the new formula should prescribe a near optimal frequency response with few exceptions.
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paper_title: Are real-ear measurements (REM) accurate when using the modified pressure with stored equalization (MPSE) method?

paper_content:

AbstractAudiologists typically verify hearing instrument fitting using real-ear measurements (REM). Recently the modified pressure with stored equalization method (MPSE) has been recommended for use when verifying open non-occluding hearing instruments. The MPSE method does not use a reference microphone to maintain loudspeaker output during real-ear measurements and is therefore susceptible to changes in the signal level at the client's ear which result from movement of the client's head and torso during the verification process. To determine the size of these errors, the real-ear unaided response (REUR) was measured prior to and following the fitting of a non-functioning hearing aid in the contralateral ear. Twenty young adults participated. Identical head positions for the two measurements should yield zero difference measures across all frequencies measured. Loudspeaker-to-client azimuths of 0° and 45° were investigated. Mean difference measures across the frequencies investigated were less than 1dB f...
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paper_title: Real-ear measurement verification for open, non-occluding hearing instruments

paper_content:

Real-ear measurements using the modified pressure method with concurrent (real-time) equalization can be inaccurate, when amplified sound leaks out of the ear canal and reaches the reference microphone. In such situations the reference microphone will detect an increased sound level and reduce the output of the loudspeaker to maintain the desired level. The risk of having errors due to leaks increases if digital feedback suppression (DFS) is used, thus achieving higher feedback-free gain levels. The following hypotheses were tested: a) using the concurrent equalization method for fitting hearing instruments with DFS may result in underestimated real-ear insertion gain (especially when using open fittings) and b) as the benefit of the DFS system increases, this error also increases. Real-ear measurements were carried out in twenty-one subjects using the modified pressure method with stored equalization as well as with concurrent equalization. The results of the study supports both hypotheses. As a conseque...
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paper_title: Real ear measurement methods for open fit hearing aids: Modified pressure concurrent equalization (MPCE) versus modified pressure stored equalization (MPSE)

paper_content:

AbstractObjective: The aim of this study was to assess differences between real ear insertion gains (REIG) measured with the modified pressure concurrent equalization (MPCE) and modified pressure stored equalization (MPSE) methods for open fittings in a typical audiology patient population. Design: REIGs were compared for the two methods using a warble tone sweep at 65 dB SPL. The differences between the two methods at 0.25, 0.5, 1, 2, 3, 4 and 6 kHz were recorded. Study sample: Eighty-three ears of a consecutive sample of 48 candidates for open-fit hearing aids were included. Results: The mean difference between MPSE and MPCE REIGs was less than 1 dB at all frequencies. Analysis of variance showed that the main effect of method was not significant, and there was no significant interaction between method and frequency. Conclusions: The results for the MPSE and MPCE methods did not differ significantly for the patients with mild-to-moderate hearing losses tested here, for whom REIGs were generally less tha...
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paper_title: Sentences for Testing Speech Intelligibility in Noise

paper_content:

A list of ten spoken Swedish sentences was computer edited to obtain new lists with exactly the same content of sound, but with new sentences. A noise was synthesized from the speech material by the computer to produce exactly the same spectrum of speech and noise. The noise was also amplitude modulated by a low frequency noise to make it sound more natural. This material was tested monaurally on 20 normal-hearing subjects. The equality in intelligibility of some of the lists was investigated. Repeated threshold measurements in noise showed a standard deviation of 0.44 dB when the learning effect was outbalanced. Only a small part of the learning effect was due to learning of the word material. Intelligibility curves fitted to the data points in noise and without noise showed maximum steepnesses of 25 and 10%/dB respectively. At constant signal to noise ratio (S/N) the best performance was achieved at a speech level of 53 dB.
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paper_title: Tolerable Hearing Aid Delays. V. Estimation of Limits for Open Canal Fittings

paper_content:

Objectives: Open canal fittings are a popular alternative to close-fitting earmolds for use with patients whose low-frequency hearing is near normal. Open canal fittings reduce the occlusion effect but also provide little attenuation of external air-borne sounds. The wearer therefore receives a mixture of air-borne sound and amplified but delayed sound through the hearing aid. To explore systematically the effect of the mixing, we simulated with varying degrees of complexity the effects of both a hearing loss and a high-quality hearing aid programmed to compensate for that loss, and used normal-hearing participants to assess the processing. Design: The off-line processing was intended to simulate the percept of listening to the speech of a single (external) talker. The effect of introducing a delay on a subjective measure of speech quality (disturbance rating on a scale from 1 to 7, 7 being maximal disturbance) was assessed using both a constant gain and a gain that varied across frequency. In three experiments we assessed the effects of different amounts of delay, maximum aid gain and rate of change of gain with frequency. The simulated hearing aids were chosen to be appropriate for typical mild to moderate high-frequency losses starting at 1 or 2 kHz. Two of the experiments used simulations of linear hearing aids, whereas the third used fast-acting multichannel wide-dynamic-range compression and a simulation of loudness recruitment. In one experiment, a condition was included in which spectral ripples produced by comb-filtering were partially removed using a digital filter. Results: For linear hearing aids, disturbance increased progressively with increasing delay and with decreasing rate of change of gain; the effect of amount of gain was small when the gain varied across frequency. The effect of reducing spectral ripples was also small. When the simulation of dynamic processes was included (experiment 3), the pattern with delay remained similar, but disturbance increased with increasing gain. It is argued that this is mainly due to disturbance increasing with increasing simulated hearing loss, probably because of the dynamic processing involved in the hearing aid and recruitment simulation. Conclusions: A disturbance rating of 3 may be considered as just acceptable. This rating was reached for delays of about 5 and 6 msec, for simulated hearing losses starting at 2 and 1 kHz, respectively. The perceptual effect of reducing the spectral ripples produced by comb-filtering was small; the effect was greatest when the hearing aid gain was small and when the hearing loss started at a low frequency.
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paper_title: Unaided and aided performance with a directional open-fit hearing aid.

paper_content:

Differences in performance between unaided and aided performance (omnidirectional and directional) were measured using an open-fit behind-the-ear (BTE) hearing aid. Twenty-six subjects without prior experience with amplification were fitted bilaterally using the manufacturer's recommended procedure. After wearing the hearing aids for one week, the fitting parameters were fine-tuned, based on subjective comments. Four weeks later, differences in performance between unaided and aided (omnidirectional and directional) were assessed by measuring reception thresholds for sentences (RTS in dB), using HINT sentences presented at 0° with R-SpaceTM restaurant noise held constant at 65dBA and presented via eight loudspeakers set 45° apart. In addition, the APHAB was administered to assess subjective impressions of the experimental aid.Results revealed that significant differences in RTS (in dB) were present between directional and omnidirectional performance, as well as directional and unaided performance. Aided om...
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paper_title: Directivity quantification in hearing aids: fitting and measurement effects.

paper_content:

OBJECTIVE: To evaluate the impact of venting, microphone port orientation, and compression on the electroacoustically measured directivity of directional and omnidirectional behind-the-ear hearing aids. In addition, the average directivity provided across three brands of directional and omnidirectional behind-the-ear hearing aids was compared with that provided by the open ear. DESIGN: Three groups of hearing aids (four instruments in each group) representing three commercial models (a total of 12) were selected for electroacoustic evaluation of directivity. Polar directivity patterns were measured and directivity index was calculated across four different venting configurations, and for five different microphone port angles. All measurements were made for instruments in directional and omnidirectional modes. Single source traditional, and two-source modified front-to-back ratios were also measured with the hearing aids in linear and compression modes. RESULTS: The directivity provided by the open (Knowles Electronics Manikin for Acoustic Research) ear was superior to that of the omnidirectional hearing aids in this study. Although the directivity measured for directional hearing aids was significantly better than that of omnidirectional models, significant variability was measured both within and across the tested models both on average and at specific test frequencies. Both venting and microphone port orientation affected the measured directivity. Although compression reduced the magnitude of traditionally measured front-to-back ratios, no difference from linear amplification was noted using a modified methodology. CONCLUSIONS: The variation in the measured directivity both within and across the directional microphone hearing aid brands suggests that manufacturer's specification of directivity may not provide an accurate index of the actual performance of all individual instruments. The significant impact of venting and microphone port orientation on directivity indicate that these variables must be addressed when fitting directional hearing aids on hearing-impaired listeners. Modified front-to-back ratio results suggest that compression does not affect the directivity of hearing aids, if it is assumed that the signal of interest from one azimuth, and the competing signal from a different azimuth, occur at the same time.
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paper_title: Preferred signal path delay and high-pass cut-off in open fittings

paper_content:

AbstractThe combination of delayed sound from a digital hearing aid with direct sound through an open or vented fitting can potentially degrade the sound quality due to audible changes in timbre and/or perception of echo. The present study was designed to test a number of delay and high-pass combinations under worst-case (i.e. most sensitive) conditions. Eighteen normal-hearing and 18 mildly hearing-impaired subjects performed the test in a paired comparison (A/B) task. The subjects were asked to select a preferred setting with respect to sound quality. The test was set in an anechoic chamber using recorded speech, environmental sounds, and own voice. Experimental hearing aids were fitted binaurally with open domes thus providing maximum ventilation. The preference data were processed using a statistical choice model that derives a ratio-scale. The analysis indicated that in these test conditions there was no change in sound quality when varying the delay in the range 5–10 ms and that there was a preferen...
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paper_title: Speech recognition in noise using bilateral open-fit hearing aids: The limited benefit of directional microphones and noise reduction

paper_content:

To investigate speech recognition performance in noise with bilateral open-fi t hearing aids and as reference also with closed earmolds, in omnidirectional mode, directional mode, and directional mode in conjunction with noise reduction. Design: A within-subject design with repeated measures across conditions was used. Speech recognition thresholds in noise were obtained for the different conditions. Study sample: Twenty adults without prior experience with hearing aids. All had symmetric sensorineural mild hearing loss in the lower frequencies and moderate to severe hearing loss in the higher frequencies. Results: Speech recognition performance in noise was not signifi cantly better with an omnidirectional microphone compared to unaided, whereas performance was signifi cantly better with a directional microphone (1.6 dB with open fi tting and 4.4 dB with closed earmold) compared to unaided. With open fi tting, no signifi cant additional advantage was obtained by combining the directional microphone with a noise reduction algorithm, but with closed earmolds a signifi cant additional advantage of 0.8 dB was obtained. Conclusions: The signifi cant, though limited, advantage of directional microphones and the absence of additional signifi cant improvement by a noise reduction algorithm should be considered when fi tting open-fi t hearing aids.
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paper_title: Acoustic Attenuation between the Ears

paper_content:

In an investigation of the acoustical insulation between the ears, various earphones and obturating devices were used. Bone conduction was shown to be chiefly responsible for the acoustical leakage between the ears. Conditions were determined under which interaural insulation could be increased considerably. Most of the measurements were performed with a compensation method which appears to give more precise results than methods previously used, and which permits phase measurements.
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paper_title: Comparison of Vent Effects between a Solid Earmold and a Hollow Earmold

paper_content:

where the thickness of the shell was the length of the vent. Vent diameters were 0, 1, 2, and 3 mm. Data Collection and Analysis: The vent effect was evaluated on real-ear aided response, real-ear occluded response during vocalization, subjective occlusion rating, insertion loss, and maximum available gain before feedback. Real-ear measurements were made with the Fonix 6500 probemicrophone real-ear system. Vocalizations from the participants were analyzed with a custom MATLAB program, and statistical analysis was conducted with SPSS software. Results: A systematic vent effect was seen with each earmold type as the nominal vent diameter changed. For the same vent diameter, the vent effect seen with the hollow earmold was greater than that of the solid earmold. Conclusions: Because of the difference in vent length (and thus acoustic mass) between a solid and a hollow earmold, the effect of vent diameter in a hollow earmold is more pronounced than that seen in a solid earmold of the same nominal vent diameter. Thus, a smaller vent diameter will be needed in a hollow earmold than in a solid earmold to achieve similar vent effects.
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paper_title: Investigation of the Auditory Occlusion Effect with Implications for Hearing Protection and Hearing Aid Design

paper_content:

Previous research has shown that auditory occlusion effects could inhibit people from using hearing protection devices or hearing aids, which raises safety and usability concerns. The objective of this study was to evaluate occlusion effects as a function of insertion depth (shallow and deep), earplug type (foam earplug and medical balloonbased earplug), and excitation source (bone vibrator and self vocal utterance). Ten participants, six male and four female, completed the experiment. The ANOVA and post hoc tests conducted on the measured occlusion effects revealed main effects of insertion depth and earplug type, as well as an interaction effect between insertion depth and earplug type. The occlusion effect of deeply inserted earplugs was smaller than that of shallowly inserted earplugs by 11.2 dB. At deep insertion, the balloon-based earplugs produced an occlusion effect of 14.9 dB while the foam earplugs produced 5.9 dB.
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paper_title: Active cancellation of occlusion: an electronic vent for hearing aids and hearing protectors.

paper_content:

The occlusion effect is commonly described as an unnatural and mostly annoying quality of the voice of a person wearing hearing aids or hearing protectors. As a result, it is often reported by hearing aid users as a deterrent to wearing hearing aids. This paper presents an investigation into active occlusion cancellation. Measured transducer responses combined with models of an active feedback scheme are first examined in order to predict the effectiveness of occlusion reduction. The simulations predict 18 dB of occlusion reduction in completely blocked ear canals. Simulations incorporating a 1 mm vent (providing passive occlusion reduction) predict a combined active and passive occlusion reduction of 20 dB. A prototype occlusion canceling system was constructed. Averaged across 12 listeners with normal hearing, it provided 15 dB of occlusion reduction. Ten of the subjects reported a more natural own voice quality and an appreciable increase in comfort with the cancellation active, and 11 out of the 12 preferred the active system over the passive system.
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paper_title: Comparison of Vent Effects between a Solid Earmold and a Hollow Earmold

paper_content:

where the thickness of the shell was the length of the vent. Vent diameters were 0, 1, 2, and 3 mm. Data Collection and Analysis: The vent effect was evaluated on real-ear aided response, real-ear occluded response during vocalization, subjective occlusion rating, insertion loss, and maximum available gain before feedback. Real-ear measurements were made with the Fonix 6500 probemicrophone real-ear system. Vocalizations from the participants were analyzed with a custom MATLAB program, and statistical analysis was conducted with SPSS software. Results: A systematic vent effect was seen with each earmold type as the nominal vent diameter changed. For the same vent diameter, the vent effect seen with the hollow earmold was greater than that of the solid earmold. Conclusions: Because of the difference in vent length (and thus acoustic mass) between a solid and a hollow earmold, the effect of vent diameter in a hollow earmold is more pronounced than that seen in a solid earmold of the same nominal vent diameter. Thus, a smaller vent diameter will be needed in a hollow earmold than in a solid earmold to achieve similar vent effects.
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paper_title: In the ear hearing device with a valve formed with an electroactive material having a changeable volume and method of operating the hearing device

paper_content:

For particularly good adaptation to a given hearing situation, an in-the-ear hearing device which has a housing with a channel in the housing that is designed as a through-opening for sound and air between the interior of the ear and the environment outside the ear, the channel is provided with a structural element for changing the size of the through-opening at at least one position. The structural element is a valve formed with electroactive material and the size of the through-opening is adjusted by application of a voltage to the valve.
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Title: Open Versus Closed Hearing-Aid Fittings: A Literature Review of Both Fitting Approaches

Section 1: Introduction
Description 1: Provide an overview of hearing loss, the role of hearing aids, and the difference between Behind-The-Ear (BTE) and In-The-Ear (ITE) hearing aids, including preliminary discussions on open and closed fittings.

Section 2: The Occlusion Effect
Description 2: Describe the physiological basis of the occlusion effect, the structure of the ear canal, and how closed earmolds exacerbate self-produced sound transmission within the ear canal.

Section 3: Quantifying the Occlusion Effect
Description 3: Differentiate between objective and subjective occlusion effects, and introduce methods used to measure these effects.

Section 4: The Objective Occlusion Effect
Description 4: Discuss the methodologies for measuring the objective occlusion effect, including real-ear measurements (REM) and frequency responses, and their relevance for open versus closed fittings.

Section 5: The Subjective Occlusion Effect
Description 5: Explore how individuals perceive their own voice when using different types of hearing aid fittings and how this subjective experience influences satisfaction with the device.

Section 6: The Acoustic Mass
Description 6: Explain the concept of acoustic mass and its impact on vent design and sound transmission in hearing aids.

Section 7: Alternative Vent Types
Description 7: Examine specific vent designs and their efficacy in reducing the occlusion effect, particularly focusing on innovative technologies like Flex-Vent TM.

Section 8: Open-Fit Hearing Aids Definition of Open-Fit Hearing Aids
Description 8: Define open-fit hearing aids, including differences in design and application within the ear canal, and elaborate on manufacturer recommendations.

Section 9: Vent Sizes
Description 9: Discuss the relationship between vent size and the occlusion effect, and provide guidelines for choosing appropriate vent sizes based on hearing loss levels.

Section 10: RIC and RITA Hearing Aids
Description 10: Compare Receiver-In-The-Canal (RIC) and Receiver-In-The-Aid (RITA) hearing aids concerning gain before feedback and user preference.

Section 11: Fitting of Open-Fit Hearing Aids
Description 11: Outline the fitting process for open-fit hearing aids, the software adjustments based on hearing loss, and challenges in achieving optimal gain.

Section 12: Advantages of Open-Fit Hearing Aids
Description 12: Detail the benefits of open-fit hearing aids, including subjective evaluations, localization, and improvements in daily life experiences.

Section 13: Disadvantages of Open-Fit Hearing Aids
Description 13: Discuss the limitations of open-fit hearing aids, such as REM accuracy, interaction between direct and amplified sounds, and reduced effectiveness of adaptive features.

Section 14: Alternative Approaches
Description 14: Introduce alternative methods and innovative designs for reducing occlusion, such as mechanical modifications and active occlusion reduction algorithms.

Section 15: Summary and Conclusions
Description 15: Provide a summary of the key points discussed in the paper, highlighting the importance of fitting choices, individual needs, and the trade-offs between open and closed hearing-aid fittings.