Deafness is a condition wherein the ability to detect certain frequencies of sound is completely or partially impaired. When applied to humans, the term hearing impaired is rejected by the Deaf Culture movement, where the terms deaf and hard-of-hearing are preferred.
Hearing sensitivity is indicated by the quietest sound that an animal can detect, called the hearing threshold. In the case of humans and some animals, according to the Hearing Aids this threshold can be accurately measured by a behavioral audio gram.
Normal hearing thresholds within any given species are not the same for all frequencies. If different frequencies of sound are played at the same amplitude, some will be perceived as loud, and others quiet or even completely inaudible. Generally, if the gain or amplitude is increased, a sound is more likely to be perceived. Ordinarily, when animals use sound to communicate, hearing in that type of animal is most sensitive for the frequencies produced by calls, or in the case of humans, speech. All levels of the auditory system contribute to this sensitivity toward certain frequencies, from the outer ear's physical characteristics to the nerves and tracts that convey the nerve impulses of the auditory portion of the brain.
A hearing loss exists when an animal has diminished sensitivity to the sounds normally heard by its species. In humans, the term hearing impairment is usually reserved for people who have relative insensitivity to sound in the speech frequencies.
No comments:
Post a Comment