Sound Class 9 MCQs help students practice important wave-based concepts from CBSE Board Class 9 Science Chapter 11. This chapter explains how sound is produced, how it travels through different mediums, and how humans hear different types of sounds. Students usually find the chapter interesting because many concepts are connected with real-life experiences like echoes, musical instruments, speakers, and vibrations.
At the same time, objective questions from this chapter can become confusing because several terms look similar during exams. Students often mix up concepts like pitch and loudness, amplitude and frequency, or ultrasonic and infrasonic sound while solving MCQs. Numerical questions based on speed of sound and echo are also commonly asked in examinations. Regular practice of Sound Class 9 MCQs helps students improve conceptual clarity and reduce mistakes in wave-related questions.
These MCQs are prepared according to the latest CBSE and NCERT syllabus. The questions help students strengthen Physics concepts, improve accuracy in objective questions, and prepare more confidently for school exams and assessments.
Important Topics Asked in Sound Class 9 MCQs
These Sound Class 9 MCQs cover all major topics from Chapter 11 of Class 9 Science.
- Production of sound
- Sound waves
- Propagation of sound
- Medium required for sound
- Frequency
- Amplitude
- Time period
- Wavelength
- Speed of sound
- Reflection of sound
- Echo
- Human ear
- Audible sound
- Infrasonic sound
- Ultrasonic sound
- SONAR applications
Some questions are concept-based while others test numerical understanding and wave behaviour.
Concepts of Confusion in Sound Class 9 MCQs
Many students lose marks because some sound-related concepts appear very similar during objective questions.
| Commonly Confused Concepts | Actual Difference |
|---|---|
| Pitch and Loudness | Pitch depends on frequency, while loudness depends on amplitude |
| Ultrasonic and Infrasonic Sound | Ultrasonic sound has frequency above human hearing range, while infrasonic sound has lower frequency |
| Amplitude and Frequency | Amplitude affects loudness, frequency affects pitch |
| Echo and Reverberation | Echo is a distinct reflected sound, while reverberation is repeated reflection of sound |
| Speed and Frequency of Sound | Frequency remains constant while speed may change with medium |
Questions based on these conceptual differences are frequently asked in school examinations.
Daily-Life Examples Related to Sound Class 9 MCQs
Many MCQs from this chapter are connected with practical observations from everyday life.
- Echoes heard in mountains are caused by reflection of sound.
- Vibrations in guitar strings produce sound.
- School bells produce sound because of vibrating metal surfaces.
- SONAR is used in ships and submarines to detect underwater objects.
- Doctors use ultrasound technology for medical imaging.
- Human beings can hear only sounds within a certain frequency range.
Such examples help students understand how sound concepts are applied in real situations.
Sound Class 9 MCQs Chapter 11 with Answers
Q. Which statement most accurately describes the fundamental mechanism by which sound is produced?
A) Rapid movement of electrons within a conductor
B) Compression and rarefaction of light waves
C) Vibration of an object that sets the surrounding medium into vibration
D) Constant emission of electromagnetic radiation
Answer: C
Explanation: Sound is produced when an object vibrates and transfers those vibrations through a medium.
Q. A sound wave travels from air into water. Which property remains constant?
A) Wavelength and frequency
B) Speed and wavelength
C) Frequency only
D) Frequency and amplitude
Answer: C
Explanation: Frequency depends on the source and does not change when sound enters another medium.
Q. Consider a sound wave represented by the equation y(x,t) equals A sine (kx minus omega t). What does amplitude represent?
A) Angular frequency
B) Amplitude
C) Wave number
D) Time period
Answer: B
Explanation: The symbol A represents the maximum displacement of particles from the mean position.
Q. Why does sound travel faster in solids than in gases?
A) Particles are more spread out
B) Solids have higher density only
C) Particles in solids are closely packed and strongly connected
D) Gases have greater elasticity
Answer: C
Explanation: Closely packed particles allow vibrations to transfer more quickly in solids.
Q. A person shouts in a valley and hears an echo after four seconds. If the speed of sound is three hundred forty metres per second, what is the distance to the reflecting surface?
A) One hundred seventy metres
B) Three hundred forty metres
C) Six hundred eighty metres
D) One thousand three hundred sixty metres
Answer: C
Explanation: Echo time includes forward and return journey. Distance equals speed multiplied by time divided by two.
Q. Which part of the human ear converts pressure variations into electrical signals?
A) Eardrum
B) Ossicles
C) Cochlea
D) Auditory nerve
Answer: C
Explanation: The cochlea converts mechanical vibrations into electrical signals.
Q. A sound wave has a frequency of twenty-five kilohertz. Into which category does it fall?
A) Infrasonic sound
B) Audible sound
C) Ultrasonic sound
D) Hypersonic sound
Answer: C
Explanation: Frequencies above twenty kilohertz are ultrasonic.
Q. The intensity of a sound wave is directly proportional to the square of its amplitude. If amplitude doubles, intensity becomes:
A) Doubled
B) Halved
C) Quadrupled
D) Unchanged
Answer: C
Explanation: Intensity varies as amplitude squared. Doubling amplitude increases intensity four times.
Q. Why can sound not travel through a perfect vacuum?
A) Vacuum absorbs sound
B) Sound is electromagnetic
C) Sound waves are mechanical and require a medium
D) Wavelength becomes infinite
Answer: C
Explanation: Sound needs particles of a medium to transfer vibrations.
Q. Why are sound-absorbing panels installed in halls?
A) Increase intensity
B) Reduce reverberation and improve clarity
C) Reflect waves uniformly
D) Convert sound into electrical energy
Answer: B
Explanation: Sound-absorbing materials reduce repeated reflections of sound.
Q. A sound wave has wavelength zero point eighty-five metres and frequency four hundred hertz. Calculate its speed.
A) Three hundred forty metres per second
B) Four hundred seventy metres per second
C) Three hundred metres per second
D) Five hundred twenty metres per second
Answer: A
Explanation: Speed equals frequency multiplied by wavelength.
Q. When a guitar string vibrates, what determines the pitch of sound?
A) Amplitude
B) Frequency
C) Speed in surrounding air
D) Total energy
Answer: B
Explanation: Pitch depends on the frequency of vibration.
Q. What is the main difference between longitudinal and transverse waves?
A) Longitudinal waves have oscillations perpendicular to propagation
B) Longitudinal waves have oscillations parallel to propagation
C) Longitudinal waves occur only in liquids
D) Transverse waves are mechanical only
Answer: B
Explanation: In longitudinal waves, particles vibrate parallel to wave direction.
Q. If hearing loss occurs due to damage to ossicles, which function is affected?
A) Direction of sound detection
B) Amplification of sound vibrations
C) Conversion to electrical signals
D) Maintenance of balance
Answer: B
Explanation: Ossicles amplify vibrations from the eardrum.
Q. A submarine emits an ultrasonic pulse that returns after zero point five seconds. If sound speed in water is one thousand five hundred metres per second, how far away is the object?
A) Three hundred seventy-five metres
B) Seven hundred fifty metres
C) One thousand five hundred metres
D) Three thousand metres
Answer: A
Explanation: Distance equals speed multiplied by time divided by two.
Q. The time period of a sound wave is zero point zero zero two seconds. What is its frequency?
A) Fifty hertz
B) Two hundred hertz
C) Five hundred hertz
D) Two thousand hertz
Answer: C
Explanation: Frequency equals one divided by time period.
Q. Which situation would result in the fastest transmission of sound?
A) Through vacuum
B) Through warm air
C) Through cold water
D) Through steel rail
Answer: D
Explanation: Sound travels fastest in solids due to tightly packed particles.
Q. A person claps in front of a large smooth wall and hears an echo. What happens if the wall is covered with thick curtains?
A) Echo becomes louder
B) Echo is heard sooner
C) Echo becomes faint or absent
D) Pitch changes
Answer: C
Explanation: Curtains absorb sound and reduce reflection.
Q. Which animal uses ultrasonic sound for navigation and hunting?
A) Elephant
B) Whale
C) Bat
D) Lion
Answer: C
Explanation: Bats use echolocation with ultrasonic waves.
Q. Two sound waves have the same frequency, but one has double amplitude. What changes?
A) Louder and higher pitch
B) Louder with same pitch
C) Softer and lower pitch
D) Softer with same pitch
Answer: B
Explanation: Amplitude affects loudness, while frequency affects pitch.
Q. Measuring the time taken for sound to travel and reflect back is based on which phenomenon?
A) Refraction
B) Diffraction
C) Interference
D) Echo
Answer: D
Explanation: Echo involves reflection of sound waves.
Q. Which sequence correctly represents the path of sound through the ear?
A) Auditory canal, eardrum, ossicles, cochlea, auditory nerve
B) Eardrum, auditory canal, ossicles, auditory nerve, cochlea
C) Ossicles, eardrum, auditory canal, cochlea, auditory nerve
D) Cochlea, auditory nerve, auditory canal, ossicles
Answer: A
Explanation: Sound enters through the auditory canal and finally reaches the auditory nerve through the cochlea.
Q. If sound travels one point five kilometres in five seconds, what is its speed?
A) Three hundred metres per second
B) Seven hundred fifty metres per second
C) Three hundred metres per second with wavelength zero point eight metres
D) Seven hundred fifty metres per second with wavelength one point two metres
Answer: A
Explanation: Speed equals distance divided by time.
Q. Infrasonic waves below twenty hertz are commonly associated with:
A) Human speech
B) Medical ultrasound
C) Elephant communication over long distances
D) Dog whistles
Answer: C
Explanation: Elephants use infrasonic waves for long-distance communication.
Q. What is the role of vocal cords in sound production?
A) Act as resonators
B) Produce sound by vibrating rapidly
C) Filter unwanted frequencies
D) Convert sound into electrical signals
Answer: B
Explanation: Vocal cords vibrate rapidly to generate sound.
Q. A sound wave completes one hundred oscillations in two seconds. What are its frequency and time period?
A) Fifty hertz and zero point zero two seconds
B) Two hundred hertz and zero point zero zero five seconds
C) Fifty hertz and zero point five seconds
D) Two hundred hertz and zero point zero two seconds
Answer: A
Explanation: Frequency equals oscillations divided by time. Time period equals reciprocal of frequency.
Q. The speed of sound in air increases with temperature. If speed is three hundred thirty-one metres per second at zero degree Celsius, what is the approximate speed at twenty-five degree Celsius?
A) Slightly less than three hundred thirty-one metres per second
B) Exactly three hundred thirty-one metres per second
C) Significantly more than three hundred thirty-one metres per second
D) Unpredictable
Answer: C
Explanation: Sound travels faster in warmer air.
Q. What is the main difference between an echo and reverberation?
A) Echo occurs in small spaces only
B) Echo occurs in large spaces while reverberation occurs in small or enclosed spaces
C) Echo is caused by absorption
D) Echo is louder than original sound
Answer: B
Explanation: Echo is a distinct reflected sound, while reverberation is persistence due to multiple reflections.
Q. Which is NOT a common application of ultrasonic waves?
A) Cleaning delicate electronic components
B) Breaking kidney stones
C) Measuring ocean depth
D) Broadcasting radio signals
Answer: D
Explanation: Radio broadcasting uses electromagnetic waves, not ultrasonic waves.
Q. A sound wave travels at three hundred forty metres per second in air. If wavelength is zero point five metres, what is its time period?
A) Zero point zero zero one four seven seconds
B) Zero point zero zero two nine four seconds
C) Zero point zero zero five eight eight seconds
D) Zero point zero one one seven six seconds
Answer: B
Explanation: Frequency equals speed divided by wavelength. Time period equals reciprocal of frequency.
Instructions Before Attempting Sound MCQs
Read wave-related terms carefully before selecting an option.
- Focus on the difference between frequency, wavelength, and amplitude.
- Practice echo-based numerical questions regularly.
- Do not confuse loudness with pitch in conceptual questions.
- Observe units properly during calculations related to speed of sound.
- Understand practical applications of ultrasonic and infrasonic sound clearly.
- Re-attempt incorrect questions after revision for better understanding.
Sometimes students understand the chapter properly but still select the wrong answer because similar sound terms create confusion during exams.
Mistakes Students Often Make in Sound MCQs
Many students lose marks in Sound Class 9 MCQs because of small conceptual mistakes and incorrect interpretation of wave properties.
- Confusing amplitude with frequency
- Incorrect understanding of pitch and loudness
- Mistakes in echo calculations
- Forgetting that sound requires a medium to travel
- Mixing ultrasonic and infrasonic sound ranges
- Incorrect assumptions related to speed of sound
- Selecting answers quickly without reading wave-related terms carefully
Most mistakes happen when students memorise definitions without understanding actual wave behaviour.
Why Practice Sound Class 9 MCQs Regularly?
Practicing Sound Class 9 MCQs regularly helps students improve conceptual understanding and solve wave-based objective questions more confidently. Since this chapter contains terminology-based and application-oriented concepts, regular MCQ practice becomes important for proper exam preparation.
- These objective questions help students:
- Improve understanding of sound waves
- Strengthen conceptual clarity in wave properties
- Prepare for school exams and tests
- Improve accuracy in Physics objective questions
- Reduce confusion between related sound concepts
Regular revision with MCQs also helps students identify weak areas more effectively before examinations.
Conclusion
Practicing Sound Class 9 MCQs regularly helps students strengthen their understanding of sound waves, vibration, echo, and wave-related concepts. These objective questions improve conceptual clarity, reduce confusion between important terms, and support better preparation for Class 9 Science examinations.