Sound Class 8 Notes CBSE Science Chapter 13 [Free PDF Download]

1. What is the Sound?

Sound is those vibrations that travel either through the air or another medium and at the same time can be heard when they reach a person's or animal's ear.

2. Musical Sound: The sound which leads to a pleasing effect on the ear.

3. Noise: The sounds which cause a jarring or an unpleasant effect.

Types of Sound:

a. Audible Sound: Those vibrations whose frequency lies between 20 Hertz to 20,000 Hertz (20 kHz) can be easily heard by the human ear.

b. Inaudible Sound: Sounds that have frequencies either above 20,000 Hertz or below 20 Hertz cannot be heard by the normal human ear.

4. The low frequency sounds which cannot be heard by ear are known as infrasonics whereas the high frequency sounds which cannot be heard are known as ultrasonics.

5. The vibration of the vocal cords in human beings produces sound.

6. Sound requires a medium to travel. This medium could be gas, liquid or solid but it cannot travel through the vacuum.

7. The eardrums in the ear are receptors of the vibrations of sound. It further sends those vibrations to the inner ear. From there, these signals are carried to the brain and interpreted as sound. 

8. Higher or unwanted sounds lead to noise pollution. Noise pollution can lead to serious health problems in human beings. For example, Lack of sleep, high blood pressure, anxiety and many other health disorders could be consequences to noise pollution. A person who is continuously exposed to a loud sound can get either temporary or even cause permanent impairment of hearing.

9. How can we manage noise pollution?

We should try to reduce noise pollution. 

a. In aircraft engines, transport vehicles, industrial machines and home appliances, silencing devices must be installed.

b. Planting more trees on the roadside and in parks can also reduce noise pollution.

10. Amplitude: It is the maximum extent of vibration of the vibrating body from its mean position.

11. Time Period: One complete to and fro movement of the pendulum around its mean position is one oscillation and the time taken by any vibrating particle to complete its one oscillation is known as time period.

12. What is the frequency?

It is the number of vibrations produced by the vibrating body in one second. SI unit of frequency - hertz (Hz).

13. What are the characteristics of Sounds?

a. Loudness: The vibrations produced in the ear which allow us to distinguish between a loud and a faint sound. The larger the amplitude of vibration, the louder the sound. Loudness of sound is directly proportional to the square of the amplitude.

b. Pitch: The characteristics of sound that make a difference between a shrill sound and a soft sound. The higher the frequency of vibration is, the higher is the pitch.

c. Quality: It is the characteristic that allows distinguishing between musical notes emitted by different musical instruments or voices even though they have the same pitch and loudness.

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In Sound Class 8 Notes, students will understand the vital role of Sound in every individual’s life. Through the Sound Notes Class 8 chapter PDF, students will comprehend how an individual can know if someone is approaching just by listening to the footsteps.

The Sound Chapter Class 8 Notes imparts knowledge about the concept of vibration and how vibrating objects produce sound. Vibration is a process of the ‘to and fro’ or the ‘front and back’ movement of an object. The Notes of Chapter Sound Class 8 PDF explain how sound travels through a medium and the reason behind its restriction while travelling through vacuum.

What is Sound?

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Sound is defined as the vibrations that can travel through any medium like air and can be heard when the vibrations reach an individual or an animal’s ear. Musical sound is a sound which produces a pleasing effect to the ear while noise is defined as a sound that creates a jarring or an unpleasant effect.

Types of Sound

There are two distinct types of sound-

a. Inaudible Sound: Inaudible sounds have a frequency above 20,000 Hz or below 20 Hz. An average human ear cannot hear a sound within this frequency level.

• Low-frequency sounds that remain inaudible to the human ear are known as Infrasonics.

• High-frequency sounds that remain inaudible to the human ear are known as Ultrasonics.

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b. Audible Sound: The audible sounds are vibrations whose frequency lies between 20 Hz and 20,000 Hz (20 kHz). The human ear can hear this frequency level.

Characteristics of Sound

There are three primary characteristics of sound:

a. Loudness: Loudness is a sensation produced in ears which enables individuals to distinguish between a faint and loud sound. If the amplitude of vibrations is larger, the sound produced will be more audible. Loudness is directly proportional to the square of the amplitude of a wave.

b. Pitch: Pitch is a characteristic of sound which enables individuals to distinguish a soft sound and a shrill sound. Higher the frequency of vibrations, higher would be the pitch and shrillness.

c. Quality: Quality is a characteristic of sound which enables individuals to distinguish the musical sounds emitted by different voices or musical instruments, even though they possess the same loudness and pitch.

What is Amplitude and Time Period?

Amplitude: is defined as the maximum extent of vibrations produced by any vibrating body from its mean position. An example of amplitude is how much a radio wave moves back and forth.

Time Period: One completed to and fro movement of the pendulum from its mean position is known as an oscillation. The total time taken by the vibrating particle to complete one oscillation is known as the Time Period.

Why are Revision Notes for Class 8 CBSE Science Chapter 13 - Sound Important?

• Vedantu’s Revision Notes for Class 8 Science Chapter 13 - “Sound” are the finest material to understand and practice the topics in the best way.

• The material carries all the information in detail and pointwise.

• All the cases of the material are solved in the simplest way which explains the term clearly.

• Vedantu Revision Notes for Class 8 Chapter 13 Sound provides all the main topics so that the student can focus on it and prepare for the exam. 

Conclusion

By immersing yourself in the Class 8 Science Notes Chapter 13 Sound, you not only prepare for your exams more efficiently but also develop a profound understanding of the subject matter. The convenience of downloading these revision notes to your smart devices empowers you to study at your own pace, making learning more flexible and accessible. Vedantu, as a dedicated platform, aims to provide students with free CBSE Solutions (NCERT) and other essential study materials. Thus, the world of knowledge is at your fingertips, with the resources you need to excel in your academic journey.