📅 Published on: 29.11.2025
Sound is an important chapter in Class 9 Science, and many conceptual as well as numerical questions are asked from it in school exams. Important questions generally focus on the nature of sound waves, differences between longitudinal and transverse waves, characteristics of sound such as amplitude, frequency, wavelength, time period, and speed. Students must also understand concepts like echo, reverberation, reflection of sound, and applications of ultrasound. Numerical questions related to speed of sound, echo distance, frequency–wavelength calculations, and time period are frequently asked in tests. Diagram-based questions on waveforms and real-life application-based questions like why we cannot hear sound on the Moon or how bats use ultrasonic waves are also very important. Practicing these questions helps strengthen understanding and improves scores in exams.
Sound Important Questions class 9 MCQs
I. Multiple Choice Questions
1. Mechanical waves can be:
2. A mechanical wave is produced through a medium:
3. A mechanical wave should possess:
4. The speed of sound is largest in:
5. The waves in rocks (i.e., earth) are of the form of:
6. Which one of the following statements is false:
7. When a person is on Moon, he cannot hear the horn of a car. The correct explanation is:
8. While travelling through air at a constant temperature, which one of the following remains unchanged:
9. The loudness of sound depends on its:
10. Pitch of a sound depends on its:
11. Of the following, the one which emits sound of highest pitch is:
12. Wavelength of ultrasonic waves in air is of the order of:
13. A wave is travelling in air. If the wavelength is 5 m, the speed is:
14. A sound wave goes from air into water; the quantity that remains unchanged is:
15. The audible sound of human beings:
16. The wavelength of adult’s voice is 0.2 m; then the frequency of child’s voice is (higher pitched):
17. A sound of frequency 5 Hz is:
18. The distance from crest to crest of any wave is:
19. The speed of sound waves in air having frequency of 512 Hz is:
20. The distance between two crests is 6 m. The speed of the wave is 360 m/s. The frequency is:
21. A boat is rocked by waves whose crests are 2.5 m apart and reach the boat once every:
22. A man standing at one end of a valley hears an echo after 3 s. The distance of the cliff is:
23. Time period of the above disturbance is:
24. Wavelength of the above disturbance is:
25. Which one of the following is NOT a correct statement?
26. A freshwater dolphin sends ultrasound to locate prey. The distance to the prey is (approx.):
27. When air temperature increases, the wavelength of sound in air:
28. A tuning fork vibrates with frequency of 256 Hz. If the temperature rises from 20°C, the speed of sound increases approximately by (per °C):
29. Sound is produced by:
30. Which one of the following is correct statement?
31. The speed of sound in air = 340 m/s. The wavelength is about 0.17 m when the frequency is:
32. A person observes an event repeating every 4 s. The frequency of the wave is:
33. In the above question, the speed of the wave is:
34. A vibrating source produces sound; its frequency lies between 20 Hz and 20 kHz.
35. Which one of the following is NOT a correct statement?
36. A dog can hear the upper limit of frequency up to:
37. Ultrasounds are longitudinal waves whose frequencies are:
38. The time interval between the incident sound and the reflected sound to hear a distinct echo is:
40. A sound is travelling at 583 m/s. If its wavelength is 1.5 cm, then:
41. In the reflection of sound, which of the following is NOT a requirement?
42. In seas & oceans, sound waves produced by vibrating objects travel through:
43. The distance of the reflecting surface from the source is:
II. Assertion–Reason Type Questions
Directions: Choose the correct option:
(i) Both A and R are true, and R is correct explanation of A
(ii) Both A and R are true, but R is not correct explanation of A
(iii) A is true, but R is false
(iv) A is false, but R is true
44. Assertion (A): Sound is produced due to vibrations of different objects.
Reason (R): Sound travels in vacuum.
45. Assertion (A): Sound energy is a form of energy.
Reason (R): It is the hearing response of the ear to the intensity of sound.
46. Assertion (A): Noise is any event which gives meaning to the term loudness.
Reason (R): It is unpleasant effect on ear.
47. Assertion (A): The frequency of wave satisfies pleasant effect.
Reason (R): The frequency never changes when wave is reflected on a hard surface.
48. Assertion (A): Waves are generally reflected by a soft surface.
Reason (R): Waves having frequency below 20 Hz are called infrasonic.
49. Assertion: Longitudinal waves whose frequencies are below 20 Hz are called infrasonic.
Sound Important Questions Class 9 (Most Expected)
1. Very Short Answer Questions (1 Mark)
Sound Important Questions Class 9 – 1 Mark
- What is vibration?
- Define frequency.
- What is the unit of loudness?
- Name the SI unit of speed of sound.
- What is the time period?
- What is the range of human hearing?
- Which medium carries sound fastest?
- Define ultrasonic sound.
- What is the speed of sound in air at room temperature?
- Which type of wave is sound?
⭐ 2. Short Answer Questions (2–3 Marks)
Sound Important Questions Class 9 – 3 Marks
- What is echo? State the condition necessary for an echo to occur.
- Distinguish between audible, inaudible, and ultrasonic sounds.
- Explain the relation between frequency and pitch.
- Why does sound travel faster in solids than in gases?
- Explain amplitude. How does amplitude affect the loudness of sound?
- What is rarefaction and compression?
- Why is sound called a mechanical wave?
- State two differences between noise and music.
- Define sonic boom.
- What happens to the sound waves when a ringing bell is placed inside a vacuum jar? Why?
⭐ 3. Long Answer Questions (5 Marks)
Sound Important Questions Class 9 – 5 Marks
-
Explain in detail how sound travels through a medium.
- Use diagram
- Compression & rarefaction
- Longitudinal wave motion
- What is reverberation? How is it reduced in big halls and auditoriums?
- Explain the structure of the human ear and how we hear sound.
-
Derive the formula for speed of sound and explain factors affecting it.
- Temperature
- Humidity
- Nature of medium
- Explain the difference between frequency, time period, wavelength, pitch, and loudness with examples.
⭐ 4. Numerical Problems (Most Expected)
Sound Important Questions Class 9 – Numericals
- A sound wave has frequency 220 Hz and speed 330 m/s. Find its wavelength.
- Sound travels 340 m/s. How much time will it take to cover a distance of 850 m?
- A boy hears an echo after 0.4 s. Calculate the distance of the reflecting wall. (Speed of sound = 340 m/s)
- A wave has wavelength 2.5 m and frequency 200 Hz. Find its speed.
Conclusion
The above Sound Important Questions Class 9 cover all concepts that are frequently asked in school exams. If students practice these questions along with diagrams, definitions, and numericals, they can easily score full marks in the chapter. Focus more on frequency, amplitude, longitudinal waves, echo, and speed of sound numericals, as these are the examiner’s favourite topics.
FAQs – Sound Important Questions Class 9
The most important topics in Sound Class 9 are pitch, loudness, frequency, echo, speed of sound, and the human ear diagram. These topics are repeatedly asked in exams and form the base for higher classes.
Generally, 2–3 numericals are asked from the Sound chapter, depending on your school exam pattern. Most of them are based on the formula: Speed = Distance / Time or v = f × λ.
Sound is a mechanical and longitudinal wave. It needs a material medium (like air, water, or solids) to travel and propagates in the form of compressions and rarefactions.
The speed of sound in air at room temperature is approximately 340 m/s. It can slightly increase with higher temperature and humidity.
Yes, the human ear diagram is a very important 5-mark question. You should practice both the labelled diagram and its explanation (outer ear, middle ear, inner ear and how sound is converted into nerve impulses).
