Absolute Threshold of Hearing

The Absolute Threshold of Hearing (ATH) is the volume level at which one can detect a particular sound 50% of the time. If one has a low absolute threshold, it means that he is able to detect small amounts of stimulation, and thus is more sensitive. If one has a high absolute threshold, then he requires more stimulation and thus is less sensitive.

$T_q(f) = 3.64 * (\frac{f}{1000})^-0.8 - 6.5e^-0.6(\frac{f}{1000}-3.3)^2 + 10^-3(\frac{f}{1000})^4$

The following are curves of the ATH for several age groups over frequency. Zwicker approximated these curves from experiments on a number of subjects:

ATH graph for different age-groups

The ATH is the simplest property of human hearing to exploit when designing a psychoacoustics model.