

Re: Al's Experiment

I am replying to this query:

>>Are the three tones, at the formants, fused...?
>>Jont Allen

When the time-varying frequencies of the formant centers are
replicated by sinusoids, a variety of perceptual effects are noted:

o listeners identify the resulting tone-complexes as several
simultaneously varying tones, as radio interference, as bad electronic
music (as opposed to "good" electronic music, one must suppose), as
equipment failure, as experimenter error, etc. Impressions reported by
subjects seem to describe the auditory forms as such, or offer
hypothetical mechanical events that might have caused such sounds;

o listeners do recognize the linguistic properties of sinewave
replicas once asked to attend to them as "synthetic speech;"

o the phonetic effects of the tonal analogs are not available from
tones presented as singletons; the first and second formant analogs
must be presented as an ensemble for listeners to obtain any phonetic

o slight departures from natural time-variation in sinewave replicas
destroys the phonetic coherence;

o the quality of the sinewave voice is reported to be unnatural, far
more unnatural than signals produced by conventional speech synthesis;

o listeners show evidence of scale normalization appropriate to vocal
tract size when they perceive sinewave vowels;

o the intonation of sinewave sentences (lacking comodulated formants,
the natural source of intonation--the fundamental frequency of
phonation--is simply absent from sinewave replicas of speech) is
attributable to the multiple use of the analog of the first formant;
apparently, it is responsible for phonetic information approximate to
the lowest oral resonance of natural speech, and it is responsible for
the pitch contour of the sentence; whether it is also heard as an
auditory form without phonetic attributes is yet to be determined;

o listeners can simultaneously resolve to the auditory form of the
tone analog of the second formant in a sinewave word as they resolve
its phonetic effects; this is a kind of duplex perception at the heart
of the recent to and fro inspired by Al Bregman this week;

o unlike the multistable percepts in the visual system, which
alternate--recall the reversals of the Rubin vase, Schroeder
staircase, Necker cube--the multistable perception of a sinewave
word is simultaneous, not successive: one is phonetic (the word), the
other an impression of the auditory forms (several tones changing in
pitch and loudness).

(Confidential to Pierre Divenyi:  This mini-tutorial on the perception
of sinewave replicas should REALLY clear out the uncertain