Hysteresis Effect
Hysteresis can be defined roughly as ‘the lagging of an effect behind its cause’. When measuring hearing thresholds it is always easier for the subject to follow a tone that is audible and decreasing in amplitude than to detect a tone that was previously inaudible.
This is because ‘top-down’ influences mean that the subject will be expecting to hear the sound and will, therefore, be more motivated with higher levels of concentration.
The ‘bottom-up’ theory explains that unwanted external (from the environment) and internal (e.g. heartbeat) noise will result in the subject only responding to the sound if the signal to noise ratio is above a certain amount.
In practice this means that when measuring threshold with sounds decreasing in amplitude, the point at which the sound becomes inaudible will always be lower than the point at which it returns to audibility. This phenomenon is known as the ‘hysteresis effect’.
Read more about this topic: Absolute Threshold Of Hearing
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