Acoustics phonetics and auditory phonetics✩

Hi there! I'm going to talk about acoustics phonetics and auditory phonetics.

• Firstly, what is acoustics phonetics?

As a result of the functioning of the mechanisms in the production of the speech, a sound wave is produced, which is transmitted through the source to the receiver. This sound wave carries all the information which is required, so the reciever can interprete the message. Sound waves exist as variations of pressure in a medium such as air and they are created by the vibration of an object, which causes the air surrounding it to vibrate. Acoustics phonetics investigates the properties of the sound wave, its duration, its fundamental frequency, or other properties of its frequency spectrum, and the relationship of these properties to other branches of phonetics (as articulatory or auditory phonetics.)

• Secondly, we're going to talk about auditory phonetics. 

If articulatory phonetics studies the way in which speech sounds are produced, auditory phonetics focuses on the perception of sounds or the way in which sounds are heard and interpreted. Before the sounds we perceive are processed and interpreted by the brain, the first anatomical organ they encounter is the ear.

The first phase starts in the outer ear, which is mainly represented by the auricle (or the pinna) and the auditory meatus (or the outer ear canal.) The outer ear canal is a tubular structure playing a double role: it protects the next segments of the ear – particularly the middle ear – and it also functions as a resonator for the sound waves that enter our auditory system.

The second phase corresponds with the middle ear, which is a cavity within the skull including a number of little anatomical structures that have an important role in audition. One of them is the eardrum. This is a diaphragm or membrane to which sound waves are directed from outside and which vibrates, acting as both a filter and a transmitter of the incoming sounds. The middle ear also contains a few tiny bones, best known as the ossicles: the mallet, the anvil and the stirrup (also called malleus, incus and stapes).  The pressure of the air entering our auditory system is converted by the vibration of the membrane (the eardrum) and the elaborate movement of the little bones that act as some sort of lever system into mechanical movement which is further conveyed to the oval window, a structure placed at the interface of the middle and inner ear. It is in the middle ear too, that a narrow duct or tube opens. Known as the Eustachian tube, it connects the middle ear to the pharynx.

The next phase is the inner ear, the main element of which is the cochlea, a cavity filled with liquid. The inner ear also includes the vestibule of the ear and the semicircular canals. Inside the cochlea there are two membranes: the vestibular membrane and the basilar membrane. It is the latter that plays a central role in the act of audition. Also essential in the process of hearing is the so-called organ of Corti, which is a group of cells, a highly sensitive structure because it includes many ciliate cells that detect the slightest vibrating movement, convert these vibrations into neural signals that are transmitted via the auditory nerves to the central receptor and controller of the entire process, the brain.

So, that's it! However, the way in which the human brain processes auditory information and, in general, the mental processes linked to speech perception and production are still largely unknown.

In the next post, Maria will show us how to describe consonant sounds. :-) 

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