question: why when I’m wearing a winter coat with headphones I get shocked through my ears?
comment: Static electricity build-up is much greater in winter because the air is so dry. If your jacket is fleece and especially if it has any wool in it, it will tend to build up static electricity as you move. Your headphones, because of the wires, are creating a conduit from the static buildup. In my case, I get a shock almost every time when I get out of my car and touch the metal outside of the door.
passages: The Allies of World War I first used infrasound to locate artillery. One of the pioneers in infrasonic research was French scientist Vladimir Gavreau. His interest in infrasonic waves first came about in his laboratory during the 1960s, when he and his laboratory assistants experienced shaking laboratory equipment and pain in the eardrums, but his microphones did not detect audible sound. He concluded it was infrasound caused by a large fan and duct system, and soon got to work preparing tests in the laboratories. One of his experiments was an infrasonic whistle, an oversized organ pipe.
  
  Section::::Sources.
   Section::::Current market.
   Section::::Hunting and firearms.
  
  The shooting of guns for recreational use can lead to hearing loss in the high frequencies. The shooting of firearms can cause damage to a variety of cochlear structures due to the high peak sound pressure levels that they generate. This can range from 140 to 175 dB .
   Heat exposure is another risk factor. As blood temperature rises, TTS increases when paired with high-frequency noise exposure. It is hypothesized that hair cells for high-frequency transduction require a greater oxygen supply than others, and the two simultaneous metabolic processes can deplete any oxygen reserves of the cochlea. In this case, the auditory system undergoes temporary changes caused by a decrease in the oxygen tension of the cochlear endolymph that leads to vasoconstriction of the local vessels. Further research could be done to see if this is a reason for the increased TTS during physical exercise that is during continued noise-exposure as well.
   BULLET::::- physiological noises heard when ear is occluded by an earphone during minimal audible pressure measurements. When the ear is covered the subject hears body noises, such as heart beat, and these may have a masking effect.
  
  Minimal audible field and minimal audible pressure are important when considering calibration issues and they also illustrate that the human hearing is most sensitive in the 2–5 kHz range.
  
  Section::::Temporal summation.
   Section::::Mammals.
  
  The production and perception of infrasound has been observed in multiple mammals, including whale, elephant, giraffe, hippopotamus, and rhinoceros. For most of these animals, observations are preliminary and their sensitivity to infrasound has not been quantified. If an animal produces a low frequency sound, and uses it in communication, it suggests the animal might also be sensitive to infrasound.
  
  Section::::Mammals.:Elephants.
   Infrasound
  
  Infrasound, sometimes referred to as low-frequency sound, is sound that is lower in frequency than 20 Hz or cycles per second, the "normal" limit of human hearing. Hearing becomes gradually less sensitive as frequency decreases, so for humans to perceive infrasound, the sound pressure must be sufficiently high. The ear is the primary organ for sensing infrasound, but at higher intensities it is possible to feel infrasound vibrations in various parts of the body.
   BULLET::::- Sound refraction: Just as a submarine can use refraction to hide its acoustic signature from surface vessels, the same principle of sound refraction can be used to prevent certain observers from hearing the noise. For example, an outdoor observer close to the ground will have sound waves refracted toward him when the ground is "cooler" than the ambient air and away from him when the ground is "hotter" than the air.
   BULLET::::- Download
  
  Section::::Music video.
   BULLET::::1. Ear Falls was once known as "Otahwaka Powitek" to the Ojibwa band. This area was believed to be haunted by the spirit of a giant beaver which lived between the upper and lower falls. It was said that when the beaver was swimming, its ears could be seen rising and falling in the foaming water.
   Infrasound sensitive fibers have very high rates of spontaneous discharge, with a mean of 115imp/s, which is much higher than the spontaneous discharge of other auditory fibers. Recordings show that discharge rates do not increase in response to infrasound stimuli but are modulated at levels comparable to the behavioral thresholds. Modulation depth is dependent on stimulus frequency and intensity. The modulation is phase locked so that the discharge rate increases during one phase of the stimulus and decreases during the other, leaving the mean discharge rate constant. Such pulse-frequency modulation allows the stimulus analysis to be independent of the peripheral tuning of the basilar membrane or the hair cells, which is already poor at low auditory frequencies. Unlike other acoustic fibers, infrasonic fibers do not show any indication of being tuned to a particular characteristic frequency.
   Neural fibers that are sensitive to infrasonic stimuli have been identified in the pigeon and their characteristics have been studied. It turns out that, although these fibers also originate in the inner ear, they are quite different from normal acoustic fibers. 
   Electrostatic headphones require a voltage source generating 100 V to over 1 kV, and are on the user's head. Since the invention of insulators, there's no actual danger. They do not need to deliver significant electric current, which further limits the electrical hazard to the wearer in case of fault.
  
  Section::::Transducer technology.:Electret.
   BULLET::::- Direct/ Reflection ratio: In enclosed rooms, two types of sound are arriving at a listener: The direct sound arrives at the listener's ears without being reflected at a wall. Reflected sound has been reflected at least one time at a wall before arriving at the listener. The ratio between direct sound and reflected sound can give an indication about the distance of the sound source.
  
  BULLET::::- Loudness: Distant sound sources have a lower loudness than close ones. This aspect can be evaluated especially for well-known sound sources.
   The reason for the discovery of this phenomenon was an accident: the aerologists working at the marine hydrometeorological stations and watercrafts drew attention to the strange pain that a person experiences when approaching the surface of a standard meteorological probe (a balloon filled with hydrogen). During one of the expeditions, this effect was demonstrated to the Soviet academician V. V. Shuleikin by the chief meteorologist V. A. Berezkin. This phenomenon drew genuine interest among scientists; in order to study it, special equipment was designed to record powerful but low-frequency vibrations that are not audible to human ears.
   Bone conduction plays a major role in underwater hearing when the head is in contact with the water (not inside a helmet), but human hearing underwater, in cases where the diver’s ear is wet, is less sensitive than in air.
   Section::::Reception.:Hearing loss.
   Furthermore, in the tip-link complex of cochlear hair cells, tonotopy is associated with gradients of intrinsic mechanical properties. In the hair bundle, gating springs determine the open probability of mechanoelectrical ion transduction channels: at higher frequencies, these elastic springs are subject to higher stiffness and higher mechanical tension in tip-links of hair cells.  This is emphasized by the division of labor between outer and inner hair cells, in which mechanical gradients for outer hair cells (responsible for amplification of lower frequency sounds) have higher stiffness and tension.
   BULLET::::- Middle ear
   Transmembrane channel-like protein 1 is a protein that in humans is encoded by the "TMC1" gene. TMC1 contains six transmembrane domains with both the C and N termini on the endoplasmic side of the membrane, as well as a large loop between domains 4 and 5. This topology is similar to that of transient receptor potential channels (TRPs), a family of proteins involved in the perception of senses such as temperature, taste, pressure, and vision. TMC1 has been located in the post-natal mouse cochlea, and knockouts for TMC1 and TMC2 result in both auditory and vestibular deficits (hearing loss and balance issues) indicating TMC1 is a molecular part of auditory transduction.
   Electrostatic and piezoelectric noise can also become an issue in exotic headphone systems, if the headphones have a relatively high input impedance compared to traditional speakers which have a nominal impedance of 8 Ohms. This is where a careful choice of insulating materials can make a difference. This type of noise is often perceived as snap, crackle and pop when mechanically manipulating or handling the headphone cord. It is often hard to tell, without actual measurements if the source of this noise is electronic or mechanical in nature.
   The ability to differentiate frequencies of two successive tones was also tested for this elephant using a similar conditioning paradigm. The elephant’s responses were somewhat erratic, which is typical for mammals in this test. Nevertheless, the ability to discriminate sounds was best at frequencies below 1 kHz particularly at measurements of 500 Hz and 250 Hz.
   In a related study, Barkat, Polley and Hensch (2011) looked at how exposure to different sound frequencies influences the development of the tonotopic map in the primary auditory cortex and the ventral medical geniculate body. In this experiment, mice were reared either in normal environments or in the presence of 7 kHz tones during early postnatal days. They found that mice that were exposed to an abnormal auditory environment during a critical period P11- P15 had an atypical tonotopic map in the primary auditory cortex.
   Section::::Characteristic acoustic impedance.:Effect of temperature.
  
  Temperature acts on speed of sound and mass density and thus on specific acoustic impedance.
  
  Section::::Characteristic acoustic impedance.:Characteristic acoustic impedance.
  
  For a "one dimensional" wave passing through an aperture with area "A", "Z" = "z"/"A", so if the wave is a progressive plane wave, then:
  
  The absolute value of this acoustic impedance is often called characteristic acoustic impedance and denoted "Z":
  
  and the characteristic specific acoustic impedance is
   BULLET::::- Eustachian Tube Dysfunction, inflammation or mass within the nasal cavity, middle ear, or eustachian tube itself
  
  BULLET::::- Otosclerosis, abnormal growth of bone in or near the middle ear
  
  BULLET::::- Middle ear tumour
  
  BULLET::::- Ossicular discontinuity as a consequence of infection or temporal bone trauma
  
  BULLET::::- Congenital malformation of the ossicles. This can be an isolated phenomenon or can occur as part of a syndrome where development of the 1st and 2nd branchial arches is seen such as in Goldenhar syndrome, Treacher Collins syndrome, branchio-oto-renal syndrome etc.
  