This small organ has quite a few surprises in store for us. We’ see that it’s literally crammed with equalisers and dynamic compressors, including a multi‑band one. It even includes an extremely efficient filter bank, as well as a highly sophisticated analogue‑to‑digital converter. Armed with this knowledge, sometimes referred to as ‘psychoacoustics’, we’ll discover numerous practical consequences for music production. Those include the choice of monitoring level, ideas for how to deal with bass frequencies in a mix, and a surprising antidote to frequency overlap.

Note that this article won’t attempt to cover psychoacoustics in its entirety. In particular, we’ll be restricting our focus to monaural audition and setting aside the notion of integration time, which is the audio equivalent of ‘persistence of vision’. Stay tuned for future articles covering stereo image issues and the very diverse uses one can make of the ear’s integration time in music production.



We’ll start our study of the ear by looking at Figure 1, on top. This drawing shows the morphology of the ear, as usually represented. This is divided into three sections. The outer ear consists of the auditory canal and the exterior of the tympanic membrane, better known as the eardrum. The malleus, incus and stapes, which are small bones often referred to as ossicles, belong to the middle ear, along with the interior of the tympanic membrane. Then there is the inner ear, which includes the cochlea and the semicircular canals. Last, we find two nerves that connect the ear to the brain. (The semicircular canals and vestibular nerves don’t relay any information relating to hearing; their purpose is to give us a sense of gravity and balance, so we’ll leave them aside.)
Figure 1: The morphology of the human ear (diagram derived from Chittka L, Brockmann A (2005): Perception Space — The Final Frontier, www.plosbiology.org).
Figure 1: The morphology of the human ear (diagram derived from Chittka L, Brockmann A (2005): Perception Space — The Final Frontier, www.plosbiology.org).
What we call ‘sound’ is in fact a progressive acoustic wave — a series of variations in air pressure, spreading out from whatever source made the sound. When these pressure variations strike the ear, they find their way through the external auditory canal to the tympanic membrane, setting it into vibration. The signal is thus converted to mechanical vibrations in solid matter. These vibrations of the tympanic membrane are transmitted to the ossicles, which in turn transmit them to the cochlea. Here the signal undergoes a second change of nature, being converted into pressure variations within liquid. These are then transformed again by specialised hair cells, which convert the liquid waves into nervous signals.

Read the rest at: http://www.soundonsound.com/sos/mar11/articles/how-the-ear-works.htm