<P> The absolute threshold of hearing (ATH) 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 . The absolute threshold is not a discrete point, and is therefore classed as the point at which a sound elicits a response a specified percentage of the time . This is also known as the auditory threshold . </P> <P> The threshold of hearing is generally reported as the RMS sound pressure of 20 micropascals, corresponding to a sound intensity of 0.98 pW / m at 1 atmosphere and 25 ° C. It is approximately the quietest sound a young human with undamaged hearing can detect at 1,000 Hz . 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, where the threshold reaches as low as − 9 dB SPL . </P> <P> Measurement of the absolute hearing threshold provides some basic information about our auditory system . The tools used to collect such information are called psychophysical methods . Through these, the perception of a physical stimulus (sound) and our psychological response to the sound is measured . </P>

What is the quietest sound that can be heard
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