Chapter 12 of Class 8 Science in the Oxford Book, titled Sound, explains how sound is produced, travels, and is heard by us. It covers key concepts like vibrations, frequency, pitch, and amplitude, along with practical examples. The solutions provided here help students understand the chapter better by offering clear explanations and accurate answers to textbook questions, making learning more effective and engaging.

Class 8 Science Chapter 12 Sound Oxford

Class 8 Science Chapter 12 Sound Oxford – Textbook Answers

II. Very Short Answer Type Questions

A. Write down the basic function of the following:

  1. Vocal folds (commonly called vocal cords)
    They vibrate to produce sound when air passes through them.
  2. Auditory nerve
    It carries sound signals from the ear to the brain for interpretation.
  3. The string in a stringed instrument
    It vibrates to produce musical sound when plucked or struck.
  4. Air column in a wind instrument
    It vibrates to produce sound when air is blown through the instrument.
  5. Skin or membrane in a percussion instrument
    It vibrates to produce sound when struck.

III. Short Answer Type Questions

  1. How can we make different sounds with our vocal folds?
    By changing the tightness and length of the vocal folds, we can change the pitch and tone of the sound produced.
  2. Why is it that sound cannot travel in vacuum?
    Sound needs a medium (solid, liquid, or gas) to travel because it moves through vibrations of particles. In vacuum, there are no particles to vibrate.
  3. What is ‘amplitude’ of a vibration?
    Amplitude is the maximum distance a vibrating object moves from its rest position.
  4. What is the unit in which time period is measured?
    Time period is measured in seconds (s).
  5. Name two wind instruments.
    Flute and trumpet.
  6. What is noise pollution?
    Noise pollution is unwanted or harmful sound that disturbs the environment and affects human health.

IV. Long Answer Type Questions

1. Give a brief description of how a sound wave propagates from the vibrating membrane of a drum to our ears.
Answer:
When the drum’s membrane is struck, it vibrates back and forth. These vibrations push and pull the air particles around it, creating compressions and rarefactions — this is a sound wave. The wave travels through the air and reaches our ears, where it causes our eardrum to vibrate, allowing us to hear the sound.

2. Explain briefly how we can ‘hear’ with our ears.
Answer:
We hear sound through the following process:

The brain interprets these signals, allowing us to recognize and understand the sound.

  • Sound waves enter the ear through the outer ear (called the pinna).
  • These waves travel through the ear canal and strike the eardrum, causing it to vibrate.
  • The vibrations are passed to the three tiny bones in the middle ear (hammer, anvil, and stirrup), which amplify the sound.
  • The vibrations then move into the inner ear, where the cochlea (a fluid-filled spiral structure) converts them into electrical signals.
  • These electrical signals are sent to the brain through the auditory nerve.
Class 8 Science Chapter 12 Sound Oxford

3. What are ‘loudness’ and ‘pitch’ of a sound? What physical characteristics are they related to?
Answer:

Loudness:

  • Loudness is the measure of how strong or weak a sound appears to our ears.
  • It tells us whether a sound is soft or loud.
  • Physical Characteristic: Loudness is related to the amplitude of the sound wave.
    • Greater amplitude → louder sound
    • Smaller amplitude → softer sound
  • Example: A drum hit hard produces a louder sound due to higher amplitude.

Pitch:

  • Pitch tells us how high or low a sound is.
  • A high-pitched sound is like a whistle, while a low-pitched sound is like a drumbeat.
  • Physical Characteristic: Pitch is related to the frequency of the sound wave.
    • Higher frequency → higher pitch
    • Lower frequency → lower pitch
  • Example: A bird’s chirp has a high pitch, while a lion’s roar has a low pitch.

4. What are infrasonic and ultrasonic waves? Give their approximate frequency ranges.
Answer:

Infrasonic Waves:

  • These are sound waves that have frequencies lower than 20 Hz.
  • Human ears cannot hear infrasonic sounds.
  • Frequency Range: Less than 20 Hz.
  • Examples: Sounds produced by earthquakes, volcanic eruptions, and some animals like whales and elephants.

Ultrasonic Waves:

  • These are sound waves that have frequencies higher than 20,000 Hz (20 kHz).
  • Humans cannot hear ultrasonic sounds either.
  • Frequency Range: More than 20,000 Hz.
  • Examples: Used in medical imaging (ultrasound), cleaning delicate objects, and by animals like bats and dolphins for navigation (echolocation).

5. What are the common sources of noise pollution? What are their harmful effects?
Answer:
Answer:

Common Sources of Noise Pollution:

  • Traffic and Vehicles – Cars, buses, trucks, motorcycles, and honking horns.
  • Industrial Activities – Factories, machines, and heavy equipment.
  • Construction Work – Use of drills, hammers, and other loud machinery.
  • Loudspeakers and Music Systems – Especially during festivals, public events, or parties.
  • Airports and Railways – Noise from airplanes taking off and landing, and trains passing by.

Harmful Effects of Noise Pollution:

  • Health Issues – Long-term exposure can lead to high blood pressure and heart problems.
  • Hearing Problems – Prolonged exposure can lead to hearing loss.
  • Stress and Irritability – Constant noise increases stress levels and mental fatigue.
  • Lack of Sleep (Insomnia) – Disturbed sleep patterns due to loud surroundings.
  • Reduced Concentration – Affects learning and productivity, especially in students.

6. How can we reduce noise pollution?
Answer:

  • Using earplugs or noise-canceling devices.
  • Controlling traffic and industrial noise with regulations.
  • Planting trees which absorb sound.
  • Using soundproof materials in buildings.
  • Limiting the use of loudspeakers and machinery.

Class-wise Solutions

Class 12:

Class 12 Physics – NCERT Solutions

Class 12 Chemistry – NCERT Solutions

Class 11:

Class 10:

Class 9:

Class 8: Class 8 Science Chapter 12 Sound Oxford &NCERT Solution- Explore

Class 7:

Class 6:

Subject-wise Solutions

Physics:

Chemistry:

Biology:

Math:

Science:

NEET BIOLOGY

For the official Class 8 Mathematics Solutions, you can visit:

  1. NCERT Textbooks (for Class 8):
ncert resources

The topic of sound is both fascinating and essential in understanding how we experience the world around us. Class 8 Science Chapter 12 Sound Oxford provides a detailed explanation of how sound is produced, travels, and is received by our ears. By studying Class 8 Science Chapter 12 Sound Oxford, students gain a strong foundation in important concepts like vibration, frequency, and amplitude.

The solutions offered here are designed to simplify the learning process and enhance comprehension of Class 8 Science Chapter 12 Sound Oxford content. Regular revision of Class 8 Science Chapter 12 Sound Oxford will help students perform better in exams and develop a deeper interest in science.