Taking a Closer Lookt at Our Auditory System

Hello, again. In this section we are going to have a closer look on our auditory system, so as to understand its basic function. Why should we learn about that? Because as listeners, we owe to know some basic things about this magnificent human mechanism. Our auditory system is one of our ‘gates’ to the outer world. It helps us pick up sound stimuli from our environment, transduce these stimuli into neural impulses and finally, carry these impulses to specific locations in the brain. In fact, its basic function, if we could summarize that, is the transduction of mechanical energy (that is, those sound vibrations in the air) into electrical energy (electrical pulses in the brain).

Now… When we say ‘mechanical energy’ we mean a sound wave that reaches our head. This sound wave is nothing more than changes in air pressure, that is caused when a sound source transmits sound. As the sound wave propagates (which means the sound wave is ‘pushing’ the air molecules), it creates regions of high and low pressure (something like the sea waves we were painting when we were little), which in our case are called crests (peaks) and troughs (valleys), respectively. Depicting such a scheme, we can understand that there are regions of where air density is increased (compressions) and regions where air density is reduced (rarefactions).

On the other hand, when we talk about ‘electrical energy’, we mean –in the case of auditory system- any sound that is transformed by hair cells into electrical signals, which finally travel along auditory nerves to the hearing centers in the brain. The exact method of the electrical impulse generation is not known, although some theories exist and new researches have been conducted.

Now, let’s see a very clear...

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...them. It is this thin wall called the ‘basilar membrane’, which runs along the whole length of the cochlea and is covered by this collection of receptor cells or else hair cells, as we’ve mentioned before. In addition to that, each hair cell responds to different sound frequencies, so that –as it is commonly stated in physics- every time the frequency of the sound wave –or better the compressional wave- matches the natural frequency of the hair cell, that nerve cell will resonate with a larger amplitude of vibration, which will then induce the cell to release an electrical impulse that passes along the auditory nerve towards the brain. There, in the brain, a process takes place that is not yer clearly understood and explained; however, the brain is capable of ‘decoding’ the qualities of the sound after he receives and interprets those electric nerve impulses.