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Hearing loss that worsens with age but is caused by factors other than normal aging, such as noise-induced hearing loss, is not presbycusis, although differentiating the individual effects of multiple causes of hearing loss can be difficult. One in three persons have significant hearing loss by age 65; by age 75, one in two.
"Conventional" pure tone audiometry (testing frequencies up to 8 kHz) is the basic measure of hearing status. [6] For research purposes, or early diagnosis of age-related hearing loss, ultra-high frequency audiograms (up to 20 kHz), requiring special audiometer calibration and headphones, can be measured. [7]
The levels are, however, not absolute, but weighted with frequency relative to a standard graph known as the minimum audibility curve which is intended to represent 'normal' hearing. This is not the best threshold found for all subjects, under ideal test conditions, which is represented by around 0 phon or the threshold of hearing on the equal ...
Hearing impairment is defined by the World Health Organization (WHO) as a hearing loss with thresholds higher than 25db in one or both ears. The degree of hearing loss is classified as mild, moderate, severe or profound. [16] The results of pure-tone audiometry are however a very good indicator of hearing impairment.
Hearing loss is a partial or total inability to hear. [5] Hearing loss may be present at birth or acquired at any time afterwards. [6] [7] Hearing loss may occur in one or both ears. [2] In children, hearing problems can affect the ability to acquire spoken language, and in adults it can create difficulties with social interaction and at work. [8]
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. Sensitivity also varies with frequency, as shown by equal-loudness contours.
There are four defined degrees of hearing loss: mild, moderate, severe and profound. Hearing loss may be divided into four types: conductive hearing loss, sensorineural hearing loss, central auditory processing disorders, and mixed types. Hearing loss may be unilateral or bilateral, of sudden onset or progressive, and temporary or permanent.
The hearing of older adults is shown to be significantly less sensitive than that of younger adults at frequencies of 4000 and 8000 Hz, corresponding approximately to the piano keys and tones of b′′′′ (B7) and b′′′′′ (B8), respectively. B8 is near the high end of the piano frequency range.