![]() ![]() Īn audiogram showing typical hearing variation from a standardized norm.Īudiograms of human hearing are produced using an audiometer, which presents different frequencies to the subject, usually over calibrated headphones, at specified levels. In women, hearing decrease is worse at low and partially medium frequencies, while men are more likely to suffer from hearing loss at high frequencies. Women have a sharper hearing loss after menopause. For example, men spend more time in noisy places, and this is associated not only with work but also with hobbies and other activities. This is due to a lot of social and external factors. Women lose their hearing somewhat less often than men. The range shrinks during life, usually beginning at around the age of eight with the upper frequency limit being reduced. Individual hearing range varies according to the general condition of a human's ears and nervous system. The human auditory system is most sensitive to frequencies between 2,000 and 5,000 Hz. Under ideal laboratory conditions, humans can hear sound as low as 12 Hz and as high as 28 kHz, though the threshold increases sharply at 15 kHz in adults, corresponding to the last auditory channel of the cochlea. The commonly stated range of human hearing is 20 to 20,000 Hz. Information gathered from the hair cells is sent via the auditory nerve for processing in the brain. These hairs line the cochlea from base to apex, and the part stimulated and the intensity of stimulation gives an indication of the nature of the sound. The compression and rarefaction of these waves set this thin membrane in motion, causing sympathetic vibration through the middle ear bones (the ossicles: malleus, incus, and stapes), the basilar fluid in the cochlea, and the hairs within it, called stereocilia. In humans, sound waves funnel into the ear via the external ear canal and reach the eardrum (tympanic membrane). ![]() Dashed line describes possible changes due to excessive hearing strain (e.g. ![]() Human hearing area in frequency and intensity. Physiological tests do not need the patient to consciously respond. The information on different mammals hearing was obtained primarily by behavioural hearing tests. A similar technique can be used when testing animals, where food is used as a reward for responding to the sound. The child learns what to do upon hearing the sound, such as placing a toy man in a boat. The test varies for children their response to the sound can be indicated by a turn of the head or using a toy. The lowest intensity they can hear is recorded. When the subject hears the sound, they indicate this by raising a hand or pressing a button. For humans, the test involves tones being presented at specific frequencies ( pitch) and intensities ( loudness). īehavioural hearing tests or physiological tests can be used to find hearing thresholds of humans and other animals. Elephants can hear sounds at 14–16 Hz, while some whales can hear infrasonic sounds as low as 7 Hz.Ī basic measure of hearing is afforded by an audiogram, a graph of the absolute threshold of hearing (minimum discernible sound level) at various frequencies throughout an organism's nominal hearing range. ![]() Some dolphins and bats, for example, can hear frequencies over 100 kHz. Several animal species are able to hear frequencies well beyond the human hearing range. Routine investigation for hearing loss usually involves an audiogram which shows threshold levels relative to a normal. Sensitivity also varies with frequency, as shown by equal-loudness contours. The human range is commonly given as 20 to 20,000 Hz, although there is considerable variation between individuals, especially at high frequencies, and a gradual loss of sensitivity to higher frequencies with age is considered normal. Hearing range describes the range of frequencies that can be heard by humans or other animals, though it can also refer to the range of levels. Logarithmic chart of the hearing ranges of some animals ![]()
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