What Is Sound?
Sound waves are essentially air vibrations. There are two fundamental characteristics of a sound wave: frequency and volume. The faster sound waves vibrate, the higher the frequency and the higher the pitch.
Frequency, in hertz (Hz), is the unit by which the depth of sound is measured (high or low). Hearing test frequencies range from 125 hertz (low-pitched sounds) to 8,000 hertz (high-pitched sounds). Typical high-frequency sounds are the chirping of the birds, falling rain, or the voices of children. Examples of low-frequency sounds are the growl of a tiger or the low rumble of an ocean liner. People with a hearing loss most often have problems understanding the higher frequencies.
The volume sets our perceived loudness of any given tone, and it’s measured in decibels (dB). Decibels represent the intensity, or loudness, of a sound. Zero decibels is silence, while 140 decibels is the loudness of a jet engine or firecracker.
How Do We Hear?
The human ear is a fascinating organ. It detects sound and converts it into electrical impulses, which are then translated by the brain into meaningful information, such as speech or music. The ear is composed of three parts: the outer ear, middle ear, and inner ear.
The Outer Ear
The outer ear consists of the auricle (also called the pinna), the ear canal, and the eardrum. The function of the outer ear is to pick up sound vibrations and send them through the ear canal to make the eardrum vibrate.
The Middle Ear
The middle ear is composed of three tiny bones called the ossicles (commonly known as hammer, anvil and stirrup) that connect the eardrum to the inner ear. The vibrations from the eardrum are amplified by these tiny bones and passed through to the inner ear.
The Inner Ear
The snail-shaped cochlea is the main component of the inner ear. Thousands of hair cells grow along the cochlear duct and convert the sound vibrations from the middle ear into electrical impulses. These impulses are sent through the auditory nerve to the brain, which perceives them as sound.
The process of hearing – from the ears picking up the sound, to the brain comprehending the converted electrical impulses – takes less than a second. Hearing loss can occur in a number of ways and they are almost all a result of a breakdown in this system.