Differences Between Sound and Noise
Sound and Noise – What’s the Difference?
Sound – consists of pressure changes in a medium (usually air), caused by vibration or turbulence. These pressure changes produce waves emanating away from the turbulent or vibrating source.
Noise – is nothing more than unwanted sound. Noise is one of the most widespread occupational health problems. It is a by-product of many industrial processes.
How is Sound Measured?
Sound is measured in two ways: decibels and frequency.
Decibels measure the pressure of sound. Frequency is related to a sound’s pitch and is measured in units called hertz (Hz), or cycles per second. The pitch of a sound — how high or low it seems — is how you perceive its frequency; the higher the pitch, the higher the frequency. High-frequency sounds are generally more annoying than low-frequency sounds and can be more harmful to hearing.
Human hearing is most sensitive to frequencies between 3,000 and 4,000 Hz. That’s why people with damaged hearing have difficulty understanding higher-pitched voices and other sounds in the 3,000 to 4,000 Hz range.
Check out the CDC Noise Meter page to get a better idea how “loud” is loud.
How Does the Ear Work?
The outer ear consists of the pinna, the ear canal, and the eardrum. When sound waves enter the outer ear, the vibrations impact the ear drum and are transmitted to the middle and inner ear.
The middle ear consists of the ossicles (malleus, incus, stapes) and the ear drum. In the middle ear three small bones called the malleus (or hammer), the incus (or anvil), and the stapes (or stirrup) amplify and transmit the vibrations generated by the sound to the inner ear.
The inner ear consists of the cochlea, the auditory (hearing) nerve, and the brain. The inner ear contains a snail-like structure called the cochlea which is filled with fluid and lined with cells with very fine hairs. These microscopic hairs move with the vibrations and convert the sound waves into nerve impulses–the result is the sound we hear. Exposure to loud noise can destroy these hair cells and cause hearing loss!
