Sound Waves

We hear a variety of sounds in our daily life. Some sounds, such as music and birds chirping, are soft and pleasant. Some sounds are loud, unpleasant and irritating. Unpleasant sounds are called noise. Excessive loud and disturbing sound is called noise pollution.

Sound is a type of wave that is caused by the vibration of objects generated. Sound needs a medium to travel from one place to another. Sound travels through solids, liquids and gases. Sound does not travel in a vacuum. Sound helps us to communicate with each other.

Facts About Sound Waves

• Sound waves are waves which require a medium to travel.

•  Mechanical waves whose frequency ranges from 20 Hz to 2000 Hz. We feel them through our ears, and we call them by the name of the sound.

Frequency Range of Sound Waves

• Infrasonic Waves: Sound waves with a frequency below 20 Hz are called infrasonic waves. Our ears cannot hear it. Such waves can be generated from sources of very large sizes.

• Audible Waves: The waves having frequencies between 20 Hz to 2000 Hz are called audible waves. Our ears can hear these waves.

• Ultrasonic Waves: Waves above 2000 Hz are called ultrasonic waves. Man's ear cannot hear it. But some animals, like - dogs, cats, bats etc., can hear it.  Due to the high frequency of these waves, it contains a lot of energy.  Also, due to their short wavelength, they can be sent very far in the form of a thin beam.

Facts About Sound Energy

• Sound is produced by the vibrations that are produced when one object exerts a force on another object.

• Sound produces a relatively low level of energy.

• If the vibrational waves of a medium change, the sound produced also changes.

• It is measured in decibels and pascals.

• The intensity of sound energy is usually measured using the perception of a normal-hearing person.

• The measurement of sound energy is related to its pressure and intensity.

Noise Pollution

Every vibrating object produces sound, and when the intensity of the sound increases, it starts feeling unpleasant to the ears. This sound is called noise pollution. For example, the noise produced by the barking of dogs and the firing of crackers is also known as noise pollution. 

Barking of a Dog

Noise causes unrest and restlessness in humans. At the same time, performance is also adversely affected. Noise is that unwanted sound which is unpleasant to the human being and creates restlessness and anxiety in him. The intensity of the disturbing sound may vary from person to person. This is called "Noise Pollution". 

Firing Crackers

Effects of Noise Pollution

Noise pollution causes irritability and anger, hearing loss, increased heart rate, blood pressure and other physical effects, etc. It is the most lethal pollutant among all types of pollutants.

Effects of Noise Pollution

• Sound causes muscle contractions that develop neurological damage, dissonance, tension, and dementia.

• Noise pollution also reduces efficiency, making you mentally and physically sick, and continuous noise of more than 100 dB damages the internal work.

Solved Questions

1. What are infrasonic waves?

Ans: Sound waves with a frequency below 20 Hz are called infrasonic waves.

2. What are ultrasonic waves?

Ans: Sound waves above 2000 Hz are called ultrasonic waves. Man's ear cannot hear it. But some animals, like - dogs, cats, bats etc., can hear it.

3. What are audible waves?

Ans: The waves having frequencies between 20 Hz to 2000 Hz are called audible waves. Our ears can hear these waves.

Summary

The propagation of sound is possible in solid, liquid, gas and plasma. Sound energy requires a medium to travel from one place to another like air and water. Noise is that unwanted sound, which is unpleasant to the human being and creates restlessness and anxiety in him. The intensity of the disturbing sound may vary from person to person. This is called noise pollution.