CBSE Class 8 Science Revision Notes Chapter 13

CBSE Class 8 Science Revision Notes Chapter 13 – Sound

CBSE Class 8 Science Chapter 13 Notes cover the important topics that highlight the significance and role of sound in daily life. Extramarks’ Class 8 Science Chapter 13 Sound Notes assist students in understanding the concepts covered in the chapter. Extramarks’ concise revision notes will benefit students preparing for their exams. Class 8 Science Sound Notes provide an overview of the chapter based on sound through brief and precise lists that help to improve and enhance preparation.

Revision Notes for CBSE Class 8 Science Chapter 13

Access CBSE Class 8 Science Chapter 13 – Sound Notes

Types of Sound:

1. Audible Sound: Sounds that are audible to human ears and have frequencies between 20 and 20,000 Hertz (20 kHz).
2. Inaudible Sound: Sounds with frequencies above 20,000 Hertz or below 20 Hertz are inaudible to the normal human ear.

• Infrasonics are low-frequency sounds that cannot be heard by the ear, whereas ultrasonics are high-frequency sounds that cannot be heard.
• The vibration of a human’s vocal chords creates sound.
• Sound travels through a medium. This medium could be a gas, a liquid, or a solid, but it cannot pass through a vacuum.
• The eardrums in the ear are sound vibration receptors. Vibrations are sent to the inner ear after they have passed through the eardrums. These signals are then carried to the brain and interpreted as sound.
• Noise pollution is characterised by consistently loud or unwelcome sounds. Serious health problems can arise from noise pollution. Sleep deprivation, hypertension, anxiety, and other health issues are all brought on by noise pollution. Hearing loss could be either temporary or permanent for someone who is frequently exposed to loud noises.

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Students will learn about the importance of sound in Sound Class 8 Notes. They will understand the role of sound in everyday life, such as how one can tell if someone is approaching them by listening to their footsteps.

The Sound Chapter Class 8 Notes will explain to students about vibration and how vibrating objects produce sound. Vibration is the process of an object’s ‘to and fro’ or ‘front and back’ movement. The Chapter Sound Class 8 Notes explain how sound travels through a medium and why it is restricted when travelling through a vacuum.

What is Sound?

The vibrations that may pass through any material like air, and these can be heard when they reach a person or an animal’s ear are referred to as sound. A musical sound is one that has an ear-pleasing effect, whereas noise is one that has an upsetting or unpleasant effect.

Types of Sound

There are two types of sound that are produced:

1. Inaudible Sound: Inaudible sounds have a frequency of more or less than 20,000 hertz. The typical human ear cannot hear a sound at this frequency level.

• Low-frequency sounds known as infrasonics are undetectable by the human ear.
• High-frequency sounds known as ultrasonics are perceptible to animals but not to humans.

1. Audible Sound: Audible noises are vibrations that have frequencies between 20 and 20,000 hertz (20 kHz). The human ear can hear sounds at this frequency level.

Characteristics of Sound

Sound has three primary characteristics:

1. Loudness: Loudness is a sensation that the ears produce that enables humans to differentiate between faint and loud sounds. The vibrations’ amplitude determines how audible the sound is going to be. The amplitude of a wave is directly proportional to its loudness.
2. Pitch: Pitch is a sound quality that allows people to distinguish between soft and shrill sounds. The higher the frequency of vibrations, the higher the pitch and shrillness.
3. Quality: Quality is a sound characteristic that allows people to distinguish musical sounds emitted by different voices or musical instruments, even if they have the same loudness and pitch.

What are Amplitude and Time Period?

Amplitude: Amplitude is the largest range of vibrations that a vibrating body can produce from its mean location. An example of amplitude is the number of times a radio wave repeats itself back and forth.

Time Period: The time period is the amount of time it takes the vibrating particle to complete one oscillation. An oscillation is a complete ‘to’ and ‘fro’ movement of the pendulum from its mean position.