Just an interesting snippet regarding a characteristic of human hearing (and all our senses). It is called neural adaptation.
Neural adaptation or sensory adaptation is a change over time in the responsiveness of the sensory system to a constant stimulus. It is usually experienced as a change in the stimulus. For example, if one rests one’s hand on a table, one immediately feels the table’s surface on one’s skin. Within a few seconds, however, one ceases to feel the table’s surface. The sensory neurons stimulated by the table’s surface respond immediately, but then respond less and less until they may not respond at all; this is an example of neural adaptation. Neural adaptation is also thought to happen at a more central level such as the cortex.
Fast and slow adaptation
One has to distinguish fast adaptation from slow adaptation. Fast adaptation occurs immediately after stimulus presentation i.e., within 100s of milliseconds. Slow adaptive processes that take minutes, hours or even days. The two classes of neural adaptation may rely on very different physiological mechanisms.
Auditory adaptation, as perceptual adaptation with other senses, is the process by which individuals adapt to sounds and noises. As research has shown, as time progresses, individuals tend to adapt to sounds and tend to distinguish them less frequently after a while. Sensory adaptation tends to blend sounds into one, variable sound, rather than having several separate sounds as a series. Moreover, after repeated perception, individuals tend to adapt to sounds to the point where they no longer consciously perceive it, or rather, “block it out”.
What this says to me is that perceived sound characteristics are variable depending on how long the person has been listening, and to what sequence of ‘stimulii’. Our senses, to some extent, are change detectors not ‘direct coupled’.
Something of a conundrum for listening-based audio equipment testing..? Our hearing begins to change the moment we start listening. It becomes desensitised to repeated exposure to a sound – one of the cornerstones of many types of listening-based testing.