Threshold of pain
The threshold of pain is the point at which pain begins to be felt. It is an entirely subjective phenomenon. The intensity at which a stimulus (e.g., heat, pressure) begins to evoke pain is the threshold intensity. So, if a hotplate on a person's skin begins to hurt at 42°C (107°F), then that is the pain threshold temperature for that bit of skin at that time. Forty-two degrees Celsius is not the pain threshold, it is the temperature at which the pain threshold was crossed.
The intensity at which a stimulus begins to evoke pain varies from individual to individual and for a given individual over time.
In hearing 
The pressure at which sound becomes painful for a listener is the pain threshold pressure for that person at that time. The threshold pressure for sound varies only slightly with frequency and can be age-dependent. Additionally, people who have been exposed to more noise/music usually have a higher threshold pressure. Threshold shift can also cause threshold pressure to vary. Prolonged exposure to sound at levels evoking pain can cause physical damage, potentially leading to hearing impairment.
The volume in acoustics refers to loudness. It is a common term for the amplitude of sound, the sound pressure level or the sound pressure. Different values for pain threshold pressure level and pain threshold pressure are found in the literature:
|Threshold of Pain|
|Sound pressure level||Sound pressure|
|120 dBSPL||20 Pa|
|130 dBSPL||63 Pa|
|134 dBSPL||100 Pa|
|137.5 dBSPL||150 Pa|
|140 dBSPL||200 Pa|
See also 
- Absolute threshold of hearing
- Dolorimeter – an instrument used to measure pain tolerance
- Exposure action value
- Pain tolerance – the amount of pain that a person can withstand before breaking down emotionally and/or physically
- "IASP Pain Terminology". International Association for the Study of Pain. Retrieved 2 September 2009.
- Nave, Carl R. (2006). "Threshold of Pain". HyperPhysics. SciLinks. Retrieved 2009-06-16.
- Truax, Barry (1999). Handbook for Acoustic Ecology (2 ed.). ARC Publications, World Soundscape Project, Simon Fraser University
- Franks, John R.; Stephenson, Mark R.; Merry, Carol J., eds. (June 1996). Preventing Occupational Hearing Loss - A Practical Guide. National Institute for Occupational Safety and Health. p. 88. Retrieved 2009-07-15
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