Noise Pollution*

Introduction

Noise pollution is unwanted, usually loud sounds which can interfere with and damage hearing. Hearing damage can occur quickly from extremely loud noises, such as explosions, or over a period of many years from constant exposure to loud sounds. Sources of noise pollution can include machinery (industrial equipment, lawn mowers, vacuum cleaners), music equipment (loud stereos, loudspeakers), and transportation vehicles (trucks, busses, planes, etc.)

Vocabulary

Amplitude: The size of a sound wave. The louder the sound, the larger the wave and the more sound energy received by the ear.

Decibels (dB):      The unit used to measure sound level (loudness).

Ear:         The organ of our body that picks up and transmits sound waves. The outer ear collects sound waves and transmits them to the ear drum. The ear drum vibrates and transmits the waves to the middle ear, causing three little bones, the hammer, anvil, and stirrup, to vibrate. These transmit the vibrations to the inner ear (cochlea) which is filled with fluid and contains tiny hairs connected to nerve fibers which carry electrical signals to the brain. The brain then interprets the signals as sound.

Ear Protectors:    Special ear plugs or coverings put in or on our ears to block out unwanted noise.

Frequency:  The number of vibrations or cycles in one second. The unit used to measure frequency is called a hertz (Hz). Also called pitch.

Noise:         Unwanted sound.

Sound:        Energy which is transmitted by pressure waves through a substance, such as air, and enters the ear to cause hearing.

Vibration:  Back and forth motion. Also called a cycle.

Sound Wave:     Transmission of energy from one vibrating air molecule to the next and then the next until it reaches the ear.

Diseases From Noise Pollution

One problem from noise pollution is sensori-neural hearing loss. This occurs when the ear is exposed to very loud noise levels (more than 85 decibels) over time. This level is reached when you cannot hear the voice of the person next to you as they talk normally. The tiny hairs located in the cochlea receive too much sound energy and can become damaged. This will result in fewer signals being transmitted to the nerve fibers, and thus to the brain. This type of hearing loss cannot be corrected. It occurs slowly over time and may not be noticed until there is already much loss.

Conductive hearing loss may occur due to injury to the middle ear. For example, the eardrum may be punctured by a thin object such as a pencil, or by a very loud explosion close to the ear. It may also be caused if the middle ear bones cannot move as well because of arthritis. This type of hearing loss can be helped with the use of a hearing aid or an operation.

What YOU Can Do

Turn down the volume. Turning down the volume on audio equipment, especially the ones placed directly on the ear, lowers the energy received by the eardrum and also on the tiny hairs in the cochlea.

Avoid loud noise situations. Either avoid loud noise situations altogether, or place barriers between you and the noise source. The thicker and heavier the barrier, the more the sound will be reduced.

Wear ear protectors. Ear plugs placed inside the ear, or ear muffs on the outside, can keep a lot of the noise from entering the ear. Tightly fitting hearing protection can reduce the sound level we hear by 25db. A good “rule of thumb” is that you should wear hearing protection if someone less than two feet away from you has to raise his or her voice for you to hear them. They should definitely be worn when using loud equipment or when attending loud concerts.

Keep at a distance. If you move twice as far away from a noise source, the sound level is decreased by four times. The further you move away, the lower the noise level.

Repair equipment. Repairing broken mufflers on cars, and making sure loud squeaking belts on machines are fixed, are other methods of limiting noise pollution.

Not all sounds are dangerous, and it is almost impossible to eliminate every source of noise pollution. However, reducing exposure to noise can help keep your hearing in the best possible condition.

*Produced by Harvard School of Public Health, Environmental Health Education Program.