How We Hear – An Introduction

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As one of the 5 traditional senses, hearing, is a very important sense for humans to have. People who cannot hear have a condition of deafness. In the past, those who could not hear were often left out of conversations and other social activities.

Thankfully, over 100 years ago, with the advent of electricity, hearing aids were developed, giving those with hearing troubles a chance to regain their social position and overall enjoyment of life. The modern hearing aid is a splendid device that is comfortable to wear, discerning in fashion, and provides the broadest technological rewards for wearers.

In order to understand what a hearing aid does for those with hearing difficulties, one must first picture how we hear. By looking at the physics of sound, the path of a sound wave, the anatomy of the human ear, differences in function between human ears and the ears of animals, hearing under different circumstances, and options to traditional hearing, one can visualize the entire complex process fairly easily.The Physics of Sound

Sound is transmitted through every medium, including liquid, solid, plasma and gas. When carried through a solid, it is both a longitudinal wave and a transverse wave. However, when sound is transmitted through the other mediums, it is only a longitudinal wave, also known as a compression wave. Longitudinal waves are areas of different pressure, deviating from the equilibrium pressure.

In order to classify a sound wave, they should be examined by the general properties of all waves.

FrequencyWavelength Period Amplitude Intensity Speed Direction

Sound travels speedily. Not nearly as fast as light, of course, but quick nonetheless. Sound travels through various mediums at different speeds, but this can always be measured by being proportional to the square root of the ratio of the stiffness of the medium to its density. Additionally, sound travels at different speeds due to the temperature of the medium. Here are a few examples.

In 20 degree air, sound travels at 767 mph. In steel, sound travels at 13,330 mph.

This is a significant difference in how sound behaves in various environs.

How loud something is can be referred to as intensity or volume, and volume is valued in a unit of measure named decibels. The essential decibel levels for those thinking about getting a hearing aid are transferred from common sources like a person talking or a TV that has been turned on. Here is a list of other sounds and decibel levels.

Normal conversation, 50 decibels

Damage will occur if exposed to this level for a long time duration, 90 decibels

Damage will occur if exposed to this level for a short time, 120 decibels

Damage to one's hearing is one of the few things which the human body cannot fix. Once some of the auditory nerves have been damaged, they are not put back or revived. For people, sound waves between the frequency range of 12Hz to 20,000Hz can be perceived as sound. For animals, the range differs, with dogs being known for their ability to hear things with a frequency above 20,000 Hz. The vibrations from a sound being produced are picked up by the outer ear, and brought into the inner ear where the ear changes pressure waves into nerve impulses. These impulses are sent to the brain and comprehended as sound. A more in-depth knowledge can be gained by looking into the anatomy of the ear.

The Anatomy of the Human Ear

The ear is divided into 3 main sections.

Outer ear. The outer ear collects the sound waves that are emitted by various people, animals, and things. It is made up of cartilage, and is sometimes pierced for human adornment purposes.

Middle ear. The middle ear is made up of an air filled cavity behind the ear drum and includes the hammer, anvil, and stirrup bones. It amplifies the sound.

Inner ear. Imbedded in the densest bone in the body, the temporal bone, and contains small cells that release chemical neurotransmitters when they are stimulated.

The process of getting a sound wave to amplifying it to translating it into a form that the brain can understand is truly amazing. Hearing aids help the middle ear by magnifying the signal enough for the inner ear to interpret it and send the message to the brain. When the brain experiences these signals, it interprets them as the various sounds which we all know. The path of sound from source to the outer ear, middle ear, inner ear, and then brain where it is perceived as a sound is a long one. However, because speed travels extremely quickly, and the nerves in the ear receive and send the signal to the brain rapidly, what we see and what we hear are in sync.

An entertaining test of the speed of sound is to watch a baseball game from 300 meters away. You will see the batter swing the bat and make contact with the pitched ball, and then a second later, you will hear the recognizable crack of the bat against the ball.

Alternatives to Hearing

While some people can benefit from hearing aids, others' hearing abilities have been permanently damaged, and hearing aids do not offer much help for them. In order to communicate with others, these people use sign language and lip reading techniques.

Sign language has a long history, with forms of this type of communication dating back thousands of years. This language has various forms as well, coordinating to a group of spoken languages.

If you have lost your hearing, hearing aids are excellent tools of our modern time which should be enjoyed.

The Hearing Aid Advice Centre, operated by Colin Forrest, is based in Livingston, Scotland and provides help to those with hearing difficulties throughout Scotland. We also provide this very valuable service throughout the UK and Ireland through carefully selected affiliate companies.

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