The threshold of pain or pain threshold is the point along a

curve In mathematics, a curve (also called a curved line in older texts) is an object similar to a line, but that does not have to be straight. Intuitively, a curve may be thought of as the trace left by a moving point. This is the definition that ...

of increasing

perception Perception () is the organization, identification, and interpretation of sensory information in order to represent and understand the presented information or environment. All perception involves signals that go through the nervous syste ...

of a stimulus at which

pain Pain is a distressing feeling often caused by intense or damaging Stimulus (physiology), stimuli. The International Association for the Study of Pain defines pain as "an unpleasant sense, sensory and emotional experience associated with, or res ...

begins to be felt. It is an entirely subjective phenomenon. A distinction must be maintained between the stimulus (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 a

visual analog scale The visual analogue scale (VAS) is a psychometrics, psychometric response scale that can be used in questionnaires. It is a measurement instrument for subjective characteristics or attitudes that cannot be directly measured. When responding to a VA ...

). Although an IASP document defines "pain threshold" as "the minimum intensity of a stimulus that is perceived as painful", it then goes on to say (contradictorily in letter although not in spirit) that:

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''. So, if a hotplate on a person's skin begins to hurt at 42 °C (107 °F), that is the ''pain 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.

Heat

The temperature at which heat becomes painful for a recipient is called the ''heat 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.

Hearing

The

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and eve ...

at which

sound In physics, sound is a vibration that propagates as an acoustic wave through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the br ...

becomes painful for a listener is the ''pain threshold pressure'' for that person at that time. The threshold pressure for sound varies with

frequency Frequency is the number of occurrences of a repeating event per unit of time. Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio ...

and can be age-dependent. 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 Hearing loss is a partial or total inability to Hearing, hear. Hearing loss may be present at birth or acquired at any time afterwards. Hearing loss may occur in one or both ears. In children, hearing problems can affect the ability to Lang ...

and

tinnitus Tinnitus is a condition when a person hears a ringing sound or a different variety of sound when no corresponding external sound is present and other people cannot hear it. Nearly everyone experiences faint "normal tinnitus" in a completely ...

. The volume in

acoustics Acoustics is a branch of physics that deals with the study of mechanical waves in gases, liquids, and solids including topics such as vibration, sound, ultrasound and infrasound. A scientist who works in the field of acoustics is an acoustician ...

refers to

loudness In acoustics, loudness is the subjectivity, subjective perception of sound pressure. More formally, it is defined as the "attribute of auditory sensation in terms of which sounds can be ordered on a scale extending from quiet to loud". The relat ...

. It is a common term for the

amplitude The amplitude of a periodic variable is a measure of its change in a single period (such as time or spatial period). The amplitude of a non-periodic signal is its magnitude compared with a reference value. There are various definitions of am ...

of sound or the

sound pressure level Sound pressure or acoustic pressure is the local pressure deviation from the ambient (average or equilibrium) atmospheric pressure, caused by a sound wave. In air, sound pressure can be measured using a microphone, and in water with a hydrophone ...

. Different values for pain threshold pressure level and pain threshold pressure are found in the literature:

References

{{DEFAULTSORT:Threshold Of Pain Hearing Pain

Heat

Hearing

See also

References