Zero decibels is the threshold of human hearing, 40 to 50 decibels is normal for a peaceful neighborhood, 70 to 80 decibels is the level adjacent to a busy urban street or 50 feet from a major freeway, and 120 to 140 decibels is a typical level at which sound is painful. Continued exposure to noise above 85 dBA (adjusted decibels) over time will cause hearing loss.
A three dBA increase doubles the amount of noise, and halves the recommended amount of exposure time. The following decibel levels of common noise sources are typical, but will vary. Noise levels above 140dBA can cause damage to hearing after just one exposure. The volume (dBA) and the length of exposure to the sound will tell you how harmful the noise is. In general, the louder the noise, the less time required before hearing loss will occur. A noise level chart showing examples of sounds with dB levels ranging from 0 to 180 decibels. Most noise levels are given in dBA, which are decibels adjusted to reflect the ear's response to different frequencies of sound. Sudden, brief impulse sounds, like many of those shown at 120 dB or greater, are often given in dB (no adjustment). Continued exposure to noise above 85 dBA (adjusted decibels) over time will cause hearing loss. The volume (dBA) and the length of exposure to the sound will tell you how harmful the noise is. In general, the louder the noise, the less time required before hearing loss will occur. According to the National Institute for Occupational Safety and Health, the maximum exposure time at 85 dBA is eight hour The decibel is commonly used in acoustics as a unit of sound pressure level. The reference pressure in air is set at the typical threshold of perception of an average human and there are common comparisons used to illustrate different levels of sound pressure. In the International System of Quantities, the decibel is defined as a unit of measurement for quantities of type level or level difference, which are defined as the logarithm of the ratio of power-or field-type quantities. Noise is measured in units of sound pressure levels called decibels, named after Alexander Graham Bell, using A-weighted sound levels (dBA). The A-weighted sound levels closely match the perception of loudness by the human ear.  0 dB is defined as the THRESHOLD OF HEARING, and it is with reference to this internationally agreed upon quantity that decibel measurements are made. In some situations, such as tape recording, a given intensity level is assigned 0 dB, and other levels are measured in negative decibels in comparison to it. Acoustics / Noise. A unit of a logarithmic scale of power or intensity called the power level or intensity level. The decibel is defined as one tenth of a bel where one bel represents a difference in level between two intensities I 1, I 0 where one is ten times greater than the other. Typical Noise Levels. Take a look at the noise levels of many common appliances and events around the house. You might be surprised. All sounds are measured at the distance that a person would typically be from the source Noise is measured in decibels (dB). An 'A-weighting' sometimes written as 'dB(A)', is used to measure average noise levels, and a 'C-weighting' or 'dB(C)', to measure peak, impact or explosive noises. You might just notice a 3 dB change in noise level, because of the way our ears work.  Zero decibels is the threshold of human hearing, 40 to 50 decibels is normal for a peaceful neighborhood, 70 to 80 decibels is the level adjacent to a busy urban street or 50 feet from a major freeway, and 120 to 140 decibels is a typical level at which sound is painful. 
http://chchearing.org/noise/common-environmental-noise-levels/ http://www.noisehelp.com/noise-level-chart.html http://chchearing.org/noise/common-environmental-noise-levels/ https://en.wikipedia.org/wiki/Decibel https://www.osha.gov/SLTC/noisehearingconservation/ http://www.sfu.ca/sonic-studio/handbook/Decibel.html http://www.nonoise.org/library/household/index.htm http://www.hse.gov.uk/noise/advice.htm https://www.codot.gov/programs/environmental/noise/noise-faqs.html
what are typical decibel levels