Hearing Loss

Noise Induced hearing loss is when our hearing is damaged by exposure to sound

Short term

Short term hearing loss occurs after exposure to loud noise such as a concert. This loss of hearing is a protective mechanism known as the Acoustic Reflex.


Long term 

Being exposed to dBs above 80 for a long period of time can cause permanent hearing loss as can regular exposure above 110dB for a minute. 


This exposure can cause an infection called tinnitus. 'It is an awareness of sound in the ears or head which is not from an external source.' (1) It can be described as a h igh pitched whistle, ring or buzz. 



The best way to combat hearing loss is to wear ear protection. As a consumer foam ear plugs will do but for musicians & technicians they're no good. High fidelity earplugs &  Custom moulded ear plugs are able to reduce noise while keeping clarity. Also take regular breaks from loud noise where you can and don't stand to close to loud speakers. 

(1) - https://www.hearinglink.org/your-hearing/tinnitus/what-is-tinnitus/

Auditory Perception

To be able to hear we need two things. 

1) A Pressurised sound wave
2) Hair Cell

This pressurised sound wave travel through the external ear and hits the Tympanic membrane (eardrum). This vibrates back and forth and causes 3 bones (Malleus, Incus & Stapes) to vibrate aswell. 

Cochlea

The Stapes is attached to the oval window which is a part of the cochlea. The Cochlea is like a coil that contains fluids. The vibration causes fluid to move towards the tip of the Cochlea.


When it get to the tip it goes back round and pushes out the round window. It then goes back and forth from the Round window to the Oval window. 

This movement causes hair cells in the Cochlea to move back and forth and that transmits a electric impulse to the brain via the auditory nerve. Hair cells closer to the tip of the cochlea respond to lower frequencies as do hair cells closer to the base respond to higher frequencies.

Partial

Fourier Analysis; 

This is a way of breaking down complex waves into partial parts.



Partial;

Partials are simple sine waves that when put together make up a more complex wave. 
















Harmonic Partial;

These are whole number pure sine waves multiples of a certain fundamental frequency. Although they are harmonic during there attack they have a lot of harmonic and inharmonic partials that fade away very quickly. 

Instruments such as Bass, Guitar and Synths are made up of harmonic partials.








Inharmonic Paritals;

These are multiples of a certain fundamental frequency that isn't a whole number. The solid line on this graph shows the inharmonic partial in comparison to where the harmonic partial would be. 

Instruments such as drums are made up of inharmonic partials.