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In many people with hyperacusis, an increased activity develops in the tensor tympani muscle in the middle ear as part of the startle response to some sounds. This lowered reflex threshold for tensor tympani contraction is activated by the perception/anticipation of loud sound, and is called tonic tensor tympani syndrome (TTTS). In some people ...
The acoustic reflex (also known as the stapedius reflex, [1] stapedial reflex, [2] auditory reflex, [3] middle-ear-muscle reflex (MEM reflex, MEMR), [4] attenuation reflex, [5] cochleostapedial reflex [6] or intra-aural reflex [6]) is an involuntary muscle contraction that occurs in the middle ear in response to loud sound stimuli or when the person starts to vocalize.
Although the ear is the primary organ for sensing low sound, at higher intensities it is possible to feel infrasound vibrations in various parts of the body. The study of such sound waves is sometimes referred to as infrasonics , covering sounds beneath 20 Hz down to 0.1 Hz (and rarely to 0.001 Hz).
Sound intensity (sound energy or propensity to cause damage to the ears) increases dramatically with proximity according to an inverse square law: halving the distance to the sound quadruples the sound intensity. In the US, 12.5% of children aged 6–19 years have permanent hearing damage from excessive noise exposure. [15]
The ear's shape also allows the sound to be heard more accurately. Many breeds often have upright and curved ears, which direct and amplify sounds. As dogs hear higher frequency sounds than humans, they have a different acoustic perception of the world. [24] Sounds that seem loud to humans often emit high-frequency tones that can scare away dogs.
The traveling wave along the basilar membrane peaks at different places along it, depending on whether the sound is low or high frequency. Due to the mass and stiffness of the basilar membrane, low frequency waves peak in the apex, while high frequency sounds peak in the basal end of the cochlea. [13]
Hyperacusis is an increased sensitivity to sound and a low tolerance for environmental noise. Definitions of hyperacusis can vary significantly; it often revolves around damage to or dysfunction of the stapes bone , stapedius muscle or tensor tympani ( eardrum ).
Sound streams arriving from the left or right (the horizontal plane) are localised primarily by the small time differences of the same sound arriving at the two ears. A sound straight in front of the head is heard at the same time by both ears. A sound to the side of the head is heard approximately 0.0005 seconds later by the ear furthest away.