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The absolute threshold of hearing (ATH), also known as the absolute hearing threshold or auditory threshold, is the minimum sound level of a pure tone that an average human ear with normal hearing can hear with no other sound present. The absolute threshold relates to the sound that can just be heard by the organism.
In neuroscience and psychophysics, an absolute threshold was originally defined as the lowest level of a stimulus – light, sound, touch, etc. – that an organism could detect. Under the influence of signal detection theory , absolute threshold has been redefined as the level at which a stimulus will be detected a specified percentage (often ...
[6] [7] [note 1] Under ideal laboratory conditions, humans can hear sound as low as 12 Hz [8] 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. [9] The human auditory system is most sensitive to frequencies between 2,000 and 5,000 Hz. [10]
Auditory fatigue is defined as a temporary loss of hearing after exposure to sound. This results in a temporary shift of the auditory threshold known as a temporary threshold shift (TTS). The damage can become permanent (permanent threshold shift, PTS) if sufficient recovery time is not allowed before continued sound exposure. [1]
This prevents the non-test ear from detecting the test signal presented to the test ear. The threshold of the test ear is measured at the same time as presenting the masking noise to the non-test ear. Thus, thresholds obtained when masking has been applied, provide an accurate representation of the true hearing threshold level of the test ear. [13]
For example, aging typically leads to hearing thresholds which get poorer as test frequencies get higher. [10] Noise induced hearing loss is typically characterized by a "notch" in the audiogram, with the poorest threshold occurring between 3000 and 6000 Hz (most often 4000 Hz) and better thresholds at lower and higher frequencies. [11]
The tone decay test (also known as the threshold tone decay test or TTDT) is used in audiology to detect and measure auditory fatigue. It was developed by Raymond Carhart in 1957. In people with normal hearing, a tone whose intensity is only slightly above their absolute threshold of hearing can be heard continuously for 60 seconds.
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-loudness contours, but is standardised in an ANSI standard to a level somewhat higher at 1 kHz . There are several definitions of the minimal audibility curve, defined in different ...