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Hearing becomes gradually less sensitive as frequency decreases, so for humans to perceive infrasound, the sound pressure must be sufficiently high. 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.
Sensitivity also varies with frequency, as shown by equal-loudness contours. Routine investigation for hearing loss usually involves an audiogram which shows threshold levels relative to a normal. Several animal species can hear frequencies well beyond the human hearing range. Some dolphins and bats, for example, can hear frequencies over 100 kHz.
Infrasound is sound at frequencies lower than the low frequency end of human hearing threshold at 20 Hz. It is known, however, that humans can perceive sounds below this frequency at very high pressure levels. [1]
Both constant exposure to loud sounds (85 dB(A) or above) and one-time exposure to extremely loud sounds (120 dB(A) or above) may cause permanent hearing loss. [9] Noise-induced hearing loss (NIHL) typically manifests as elevated hearing thresholds (i.e. less sensitivity or muting) between 3000 and 6000 Hz, centred at 4000 Hz. As noise damage ...
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]
The second component is known as "distortion" or "clarity loss" due to selective frequency loss. [8] Consonants, due to their higher frequency, are typically affected first. [7] For example, the sounds "s" and "t" are often difficult to hear for those with hearing loss, affecting clarity of speech. [9] NIHL can affect either one or both ears.
It is approximately the quietest sound a young human with undamaged hearing can detect at 1 kHz. [4] The threshold of hearing is frequency-dependent and it has been shown that the ear's sensitivity is best at frequencies between 2 kHz and 5 kHz, [5] where the threshold reaches as low as −9 dB SPL. [6] [7] [8]
Although pitch retrieval mechanisms in the auditory system are still a matter of debate, [76] [115] TFS n information may be used to retrieve the pitch of low-frequency pure tones [75] and estimate the individual frequencies of the low-numbered (ca. 1st-8th) harmonics of a complex sound, [116] frequencies from which the fundamental frequency of ...