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Thethreshold of pain orpain threshold is the point along acurve of increasingperception of astimulus at whichpain begins to be felt. It is an entirely subjective phenomenon. A distinction must be maintained between thestimulus (an external thing that can be directly measured, such as with a thermometer) and the person's or animal's resulting pain perception (an internal, subjective thing that can sometimes be measured indirectly, such as with avisual analog scale). Although anIASP document defines "pain threshold" as "the minimum intensity of a stimulus that is perceived as painful",[1] it then goes on to say (contradictorily in letter although not in spirit) that:[1]
Traditionally the threshold has often been defined, as we defined it formerly, as the least stimulus intensity at which a subject perceives pain. Properly defined, the threshold is really the experience of the patient, whereas the intensity measured is an external event. It has been common usage for most pain research workers to define the threshold in terms of the stimulus, and that should be avoided ... The stimulus is not pain (q.v.) and cannot be a measure of pain.
Although the phrasing may not convey it perfectly, the distinction clearly meant is the aforementioned one between the stimulus and the perception of it. The intensity at which a stimulus (e.g., heat, pressure) begins to evoke pain is thus called by a separate term,threshold intensity.[1] So, if a hotplate on a person's skin begins to hurt at 42 °C (107 °F), that is thepain threshold temperature for that bit of skin at that time. It is not the pain threshold (which is internal/subjective) but the temperature at which the pain threshold was crossed (which is external/objective).
The intensity at which a stimulus begins to evoke pain varies from individual to individual and for a given individual over time.
The temperature at which heat becomes painful for a recipient is called theheat pain threshold for that person at that time.One study showed that morning-oriented people have higher pain threshold for heat as compared to evening-oriented individuals.[2]
Thepressure at whichsound becomes painful for a listener is thepain threshold pressure for that person at that time. The threshold pressure for sound varies withfrequency and can be age-dependent. People who have been exposed to more noise/music usually have a higher threshold pressure.[3]Threshold shift can also cause threshold pressure to vary.[4] Prolonged exposure to sound at levels evoking pain can cause physical damage, potentially leading tohearing impairment andtinnitus.
The volume inacoustics refers toloudness. It is a common term for theamplitude of sound or thesound pressure level. Different values for pain threshold pressure level and pain threshold pressure are found in the literature:[5][6][4]
| 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 |
the threshold for pain is between 120 and 140 dB SPL.
The upper limit for a tolerable intensity of sound rises substantially with increasing habituation. Moreover, a variety of subjective effects are reported, such as discomfort, tickle, pressure, and pain, each at a slightly different level. As a simple engineering estimate it can be said that naive listeners reach a limit at about 125 dB SPL and experienced listeners at 135 to 140 dB.
A nominal figure for the threshold of pain is 130 decibels ... Some sources quote 120 dB as the pain threshold