The threshold of pain or pain threshold is the point along a curve of increasing perception of a stimulus at which pain 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). 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. °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).So, if a hotplate on a person's skin begins to hurt at 42
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 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.
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 with frequency 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.
The volume in acoustics refers to loudness. It is a common term for the amplitude of sound or the sound pressure level. 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|
The decibel is a relative unit of measurement corresponding to one tenth of a bel (B). It is used to express the ratio of one value of a power or root-power quantity to another, on a logarithmic scale. A logarithmic quantity in decibels is called a level. Two signals whose levels differ by one decibel have a power ratio of 101/10 or an amplitude ratio of 101⁄20 (1.12202).
The phon is a unit of loudness for pure tones. Human sensitivity to sound is variable across different frequencies; therefore, although two different tones may have identical sound intensity, they may be psychoacoustically perceived as differing in loudness. The purpose of the phon is to provide a standard measurement for perceived intensity. The phon is psychophysically matched to a reference frequency of 1 kHz. In other words, the phon matches the sound pressure level (SPL) in decibels of a similarly perceived 1 kHz pure tone. For instance, if a sound is perceived to be equal in intensity to a 1 kHz tone with an SPL of 50 dB, then it has a loudness of 50 phons, regardless of its physical properties. The phon was proposed in DIN 45631 and ISO 532 B by S. S. Stevens.
The absolute threshold of hearing (ATH) is the minimum sound level of a pure tone that an average human ear with normal hearing can hear with no other sound present. The absolute threshold relates to the sound that can just be heard by the organism. The absolute threshold is not a discrete point, and is therefore classed as the point at which a sound elicits a response a specified percentage of the time. This is also known as the auditory threshold.
Psychophysics quantitatively investigates the relationship between physical stimuli and the sensations and perceptions they produce. Psychophysics has been described as "the scientific study of the relation between stimulus and sensation" or, more completely, as "the analysis of perceptual processes by studying the effect on a subject's experience or behaviour of systematically varying the properties of a stimulus along one or more physical dimensions".
In acoustics, loudness is the subjective perception of sound pressure. More formally, it is defined as, "That attribute of auditory sensation in terms of which sounds can be ordered on a scale extending from quiet to loud." The relation of physical attributes of sound to perceived loudness consists of physical, physiological and psychological components. The study of apparent loudness is included in the topic of psychoacoustics and employs methods of psychophysics.
Sound pressure or acoustic pressure is the local pressure deviation from the ambient atmospheric pressure, caused by a sound wave. In air, sound pressure can be measured using a microphone, and in water with a hydrophone. The SI unit of sound pressure is the pascal (Pa).
In physiology, a stimulus is a detectable change in the physical or chemical structure of an organism's internal or external environment. The ability of an organism or organ to detect external stimuli, so that an appropriate reaction can be made, is called sensitivity. Sensory receptors can receive information from outside the body, as in touch receptors found in the skin or light receptors in the eye, as well as from inside the body, as in chemoreceptors and mechanoreceptors. When a stimulus is detected by a sensory receptor, it can elicit a reflex via stimulus transduction. An internal stimulus is often the first component of a homeostatic control system. External stimuli are capable of producing systemic responses throughout the body, as in the fight-or-flight response. In order for a stimulus to be detected with high probability, its level of strength must exceed the absolute threshold; if a signal does reach threshold, the information is transmitted to the central nervous system (CNS), where it is integrated and a decision on how to react is made. Although stimuli commonly cause the body to respond, it is the CNS that finally determines whether a signal causes a reaction or not.
Stimulus modality, also called sensory modality, is one aspect of a stimulus or what is perceived after a stimulus. For example, the temperature modality is registered after heat or cold stimulate a receptor. Some sensory modalities include: light, sound, temperature, taste, pressure, and smell. The type and location of the sensory receptor activated by the stimulus plays the primary role in coding the sensation. All sensory modalities work together to heighten stimuli sensation when necessary.
Sensory neurons, also known as afferent neurons, are neurons in the nervous system, that convert a specific type of stimulus, via their receptors, into action potentials or graded potentials. This process is called sensory transduction. The cell bodies of the sensory neurons are located in the dorsal ganglia of the spinal cord.
An equal-loudness contour is a measure of sound pressure level, over the frequency spectrum, for which a listener perceives a constant loudness when presented with pure steady tones. The unit of measurement for loudness levels is the phon and is arrived at by reference to equal-loudness contours. By definition, two sine waves of differing frequencies are said to have equal-loudness level measured in phons if they are perceived as equally loud by the average young person without significant hearing impairment.
The acoustic reflex is an involuntary muscle contraction that occurs in the middle ear in response to loud sound stimuli or when the person starts to vocalize.
Audiometry is a branch of audiology and the science of measuring hearing acuity for variations in sound intensity and pitch and for tonal purity, involving thresholds and differing frequencies. Typically, audiometric tests determine a subject's hearing levels with the help of an audiometer, but may also measure ability to discriminate between different sound intensities, recognize pitch, or distinguish speech from background noise. Acoustic reflex and otoacoustic emissions may also be measured. Results of audiometric tests are used to diagnose hearing loss or diseases of the ear, and often make use of an audiogram.
An audiogram is a graph that shows the audible threshold for standardized frequencies as measured by an audiometer. The Y axis represents intensity measured in decibels and the X axis represents frequency measured in hertz. The threshold of hearing is plotted relative to a standardised curve that represents 'normal' hearing, in dB(HL). They are not the same as equal-loudness contours, which are a set of curves representing equal loudness at different levels, as well as at the threshold of hearing, in absolute terms measured in dB SPL.
In psychophysics, sensory threshold is the weakest stimulus that an organism can detect. Unless otherwise indicated, it is usually defined as the weakest stimulus that can be detected half the time, for example, as indicated by a point on a probability curve. Methods have been developed to measure thresholds in any of the senses.
Hyperpathia is a clinical symptom of certain neurological disorders wherein nociceptive stimuli evoke exaggerated levels of pain. This should not be confused with allodynia, where normally non-painful stimuli evoke pain.
Auditory masking occurs when the perception of one sound is affected by the presence of another sound.
In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid.
Sensation is the physical process during which sensory systems respond to stimuli and provide data for perception. A sense is any of the systems involved in sensation. During sensation, sense organs engage in stimulus collection and transduction. Sensation is often differentiated from the related and dependent concept of perception, which processes and integrates sensory information in order to give meaning to and understand detected stimuli, giving rise to subjective perceptual experience, or qualia. Sensation and perception are central to and precede almost all aspects of cognition, behavior and thought.
Psychoacoustics is the branch of psychophysics involving the scientific study of sound perception and audiology—how humans perceive various sounds. More specifically, it is the branch of science studying the psychological responses associated with sound. Psychoacoustics is an interdisciplinary field of many areas, including psychology, acoustics, electronic engineering, physics, biology, physiology, and computer science.
As long as humans have experienced pain, they have given explanations for its existence and sought soothing agents to dull or cease the painful sensation. Archaeologists have uncovered clay tablets dating back as far as 5,000 BC which reference the cultivation and use of the opium poppy to bring joy and cease pain. In 800 BC, the Greek writer Homer wrote in his epic, The Odyssey, of Telemachus, a man who used opium to soothe his pain and forget his worries. While some cultures researched analgesics and allowed or encouraged their use, others perceived pain to be a necessary, integral sensation. Physicians of the 19th century used pain as a diagnostic tool, theorizing that a greater amount of personally perceived pain was correlated to a greater internal vitality, and as a treatment in and of itself, inflicting pain on their patients to rid the patient of evil and unbalanced humors. This article focuses both on the history of how pain has been perceived across time and culture, but also how malleable an individual's perception of pain can be due to factors like situation, their visual perception of the pain, and previous history with pain.
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