Sound – Complete Guide For Class 8 Science Chapter 10

Welcome to iPrep, your Learning Super App! Our learning resources for the chapter, Sound Class 8th chapter 10 are designed to ensure that you grasp this concept with clarity and perfection. Whether you’re studying for an upcoming exam or strengthening your concepts, our engaging animated videos, practice questions and notes offer you the best of integrated learning with interesting explanations and examples.

The chapter on Sound in Class 8 Science introduces students to the fact that Sound is a form of energy produced by vibrating objects. Sound plays an essential role in our daily lives, facilitating communication and providing a vast array of auditory experiences. From the soothing melodies of music to the natural sounds around us, sound is a fundamental part of the human experience. Understanding the properties of sound, such as its production, propagation, reflection, and absorption, helps us appreciate the complexities of this fascinating phenomenon and its impact on our world.

The Role of Musical Instruments

Musical instruments are a prime example of how sound is produced and manipulated to create music. Instruments like the harmonium, flute, sitar, and tabla produce sound through vibrations.

Sound Production

Sound is generated when an object vibrates, creating waves in the surrounding medium (air, water, or solids). The vibration, also known as to-and-fro or back-and-forth motion, ceases when the object stops vibrating, and the sound disappears.

Activities Demonstrating Sound Production

1. Frying Pan Experiment: Hang a frying pan without it touching any surface, strike it with a stick, and feel the vibrations that produce sound.
2. Rubber Band on Pencil Box: Stretch a rubber band around a pencil box, insert two pencils, and pluck the rubber band to hear the sound it produces.
3. Water Dish Experiment: Strike the edge of a water-filled metal dish with a spoon and observe the waves created on the water surface as the dish vibrates.
4. Jaltrang: Fill several glass tumblers with varying water levels and strike them with a pencil to produce pleasant sounds akin to a jaltarang.

Instruments like the sitar and mridangam demonstrate how sound is not just produced by strings or membranes but also involves the entire body of the instrument, which resonates to amplify the sound.

Human Sound Production

Humans produce sound using the larynx or voice box, where two vocal cords stretch across a slit. When air from the lungs passes through, it causes the cords to vibrate, producing sound. The quality of the voice changes based on whether the vocal cords are tight and thin or loose and thick.

Activities Demonstrating Human Sound Production

1. Rubber Strips: Place two rubber strips over each other, stretch them, and blow air through the gap to produce sound.
2. Paper Slit: Hold a piece of paper with a slit between your fingers and blow through it to create sound.

Sound Propagation

Sound requires a medium (solid, liquid, or gas) to travel. It cannot travel through a vacuum, emphasizing the need for a medium to carry sound waves from one place to another.

Activities Demonstrating Sound Propagation

1. Mobile Phone in Glass: Place a mobile phone in a glass tumbler, call it, and notice the loud sound. Reduce the air in the glass to observe the sound becoming fainter.
2. Bell in Water: Shake a bell in a water-filled container and listen to the sound by putting your ear close to the water’s surface.

3. Rod Experiment: Hold one end of a rod to your ear while someone scratches the other end, demonstrating how sound travels through solids.
4. String Telephone: Create a simple telephone using a string and two boxes to understand how sound travels through a medium.

How We Hear

The human ear functions like a funnel, channeling sound waves to the eardrum, a thin membrane that vibrates upon receiving sound. These vibrations are sent to the inner ear and then to the brain, allowing us to perceive sound.

Eardrum Protection

The eardrum can be damaged by inserting sharp objects into the ear, potentially impairing hearing. It’s important to protect the eardrum from such harm.

Key Terms in Sound

• Oscillatory Motion: The back-and-forth motion that generates sound waves.
• Frequency: The number of oscillations per second, measured in Hertz (Hz).
• Amplitude: The maximum displacement from the rest position, determining the sound’s loudness.

Characteristics of Sound

• Loudness: Depends on the amplitude of vibrations; larger amplitude results in louder sound. It is measured in decibels (dB).
• Pitch: Related to frequency; higher frequency results in a higher pitch, while lower frequency results in a lower pitch.
• Audible Range: Human ears can detect sounds ranging from 20 Hz to 20,000 Hz.

Noise vs. Music

• Noise: Unpleasant sounds, such as construction work or vehicle horns.
• Music: Pleasant sounds, such as those produced by musical instruments.

Noise Pollution

Excessive or unwanted sounds in the environment contribute to noise pollution, which can lead to health issues like sleep disturbances, hypertension, and hearing impairment. Controlling noise pollution involves minimizing noise sources and implementing silencing devices in machinery and vehicles. 

This comprehensive guide on the concepts of friction explores the various types, causes, and effects of friction, arming readers with the knowledge to both minimize and harness its power in different scenarios. Understanding the science of sound enhances our appreciation of its role in life and technology. By recognizing its production, propagation, and effects, we can better manage and utilize sound in various applications, from communication and entertainment to industrial processes and environmental monitoring.