Introduction
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.
FAQs on Sound Waves
1. How is sound produced?
Sound is produced when an object vibrates. A vibration is a rapid back-and-forth movement. For example, when you pluck a guitar string, it vibrates, causing the air around it to vibrate and create sound waves. Similarly, our vocal cords vibrate when we speak. You can learn more about how sound is produced through the vibration of various objects.
2. What are sound waves?
Sound waves are invisible waves of energy that travel through a medium like air, water, or solids. They are created by vibrations. When an object vibrates, it pushes and pulls on the particles of the medium next to it, creating a travelling disturbance. This disturbance, which travels outwards from the source, is the sound wave that our ears detect. For more details, you can explore the facts about sound waves.
3. What are some examples of sound in our daily life?
We are surrounded by sounds every day. Some common examples include:
The ringing of a school bell.
The sound of people talking or laughing.
Music playing from a radio or phone.
The barking of a dog.
The sound of rain falling.
The honking of a car horn.
4. What is the difference between a loud sound and a soft sound?
The difference between a loud and soft sound is determined by the amplitude of the sound wave. A sound wave with a large amplitude carries more energy and is perceived as a loud sound, like a jet engine. A sound wave with a small amplitude carries less energy and is perceived as a soft sound, like a whisper. The loudness of sound is a key characteristic that helps us distinguish different sounds.
5. What is the difference between a high-pitched sound and a low-pitched sound?
The difference between a high-pitched and low-pitched sound is its frequency, which is how fast the sound source is vibrating.
High-pitched sounds (like a whistle or a bird's chirp) are produced by rapid vibrations, which means they have a high frequency.
Low-pitched sounds (like a drum or a lion's roar) are produced by slow vibrations, meaning they have a low frequency.
A sound's pitch is what makes it sound "high" or "low" to our ears.
6. Why can't we hear sound in space?
We cannot hear sound in space because space is a vacuum, which means it is empty of matter like air. Sound waves are mechanical waves, which means they need particles (like air or water molecules) to travel by vibrating them. Since there are no particles in the vacuum of space to carry the vibrations, sound waves cannot propagate. This is a fundamental concept that shows why sound needs a medium to travel.
7. How do sound waves travel from a source, like a speaker, to our ears?
When a speaker produces sound, its cone vibrates back and forth. This pushes on the nearby air particles, squeezing them together (a region called compression) and then pulling them apart (a region called rarefaction). This creates a chain reaction where each particle bumps into the next, passing the vibration along. This travelling pattern of compressions and rarefactions is the sound wave that reaches your eardrum, making it vibrate so you can hear.
8. What is the difference between a pleasant sound, like music, and an unpleasant sound, like noise?
The main difference lies in the pattern of the vibrations. Pleasant sounds, like music, are typically made of regular, organised, and periodic vibrations that have a clear pitch and rhythm. Noise, on the other hand, is made of irregular, disorganised, and random vibrations. It is often unpleasant to hear and lacks a clear pattern, such as the sound of heavy traffic or construction work.
9. How can some animals, like dogs and bats, hear sounds that humans cannot?
Animals like dogs and bats can hear sounds that are outside the range of human hearing because their ears are sensitive to different frequencies. Humans can typically hear sounds between 20 Hz and 20,000 Hz. Sounds with frequencies above 20,000 Hz are called ultrasound, while those below 20 Hz are called infrasound. Bats use ultrasound for navigation (echolocation), and dogs can hear high-frequency whistles that are completely silent to us.
10. What is an echo and why does it happen?
An echo is the repetition of a sound caused by the reflection of sound waves off a hard, distant surface, like a wall, cliff, or large building. When you shout in a large empty hall, the sound waves travel, hit the far wall, and bounce back to your ears. If the time delay between the original sound and the reflected sound is long enough for our brain to distinguish them, you hear the sound again as an echo.
