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12. Sound is one of the most important chapters in the Class 9 Science English NCERT Solutions curriculum. This chapter plays a significant role in helping students build a strong conceptual foundation while preparing for school examinations, class tests, unit tests, half-yearly examinations, annual examinations, and CBSE board assessments. The chapter has been carefully designed according to the latest NCERT syllabus, making it an essential part of every student's study plan.

The 12. Sound - Class 9 Science English NCERT Solutions available on ATP Education explain every question in a simple, accurate, and step-by-step manner. Each answer is prepared according to the latest CBSE guidelines so that students can understand the concepts clearly without confusion. Whether you are completing your homework, revising before examinations, or strengthening your understanding of the subject, these solutions provide reliable academic support throughout your learning journey.

One of the biggest advantages of studying 12. Sound is that it helps students understand important concepts, definitions, examples, and textbook exercises in an organized way. Instead of memorizing answers, students learn how to develop logical thinking, improve analytical skills, and write well-structured answers in examinations. This chapter also helps improve problem-solving ability and encourages conceptual learning, which is essential for scoring higher marks in school and competitive examinations.

Our Class 9 Science NCERT Solutions cover all textbook questions, important exercise questions, and chapter-wise explanations in English Medium. Every solution is written in easy-to-understand language, allowing students to revise the chapter quickly before examinations. Regular practice of these solutions improves confidence, strengthens subject knowledge, and reduces examination stress.

Students preparing for school assessments should carefully study 12. Sound because questions from this chapter are frequently asked in objective questions, short answer questions, long answer questions, competency-based questions, and case-study questions. Understanding the concepts explained in this chapter also helps students connect related topics from other chapters, making overall learning more effective and meaningful.

At ATP Education, we continuously update our Class 9 Science English NCERT Solutions according to the latest NCERT textbooks and CBSE curriculum. Students can confidently use these chapter-wise solutions for daily study, homework assistance, quick revision, examination preparation, and self-learning. By studying 12. Sound thoroughly and practising every question regularly, students can strengthen their concepts, improve writing skills, and achieve better academic performance in both school and board examinations.

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12. Sound - Class 9 Science English NCERT Solutions

12. Sound

Chapter Review

Class 9 Science English Updated : 06 March 2026

Chapter Review: 

  • Sound is produced by Vibrating objects.
  • The matter or substance through which sound is transmitted is called a medium. 
  • In Solid Medium Sound transmits fast.
  • School bell is made of metal. When a wooden hammer is stroked on it the metal produces vibrations, which causes sound.
  • A sound passes through a medium, the medium shows its physical motion and vibrates. So the sound waves are called the mechanical waves.
  • Frequency – The number of oscillations completed by sound wave in per unit time is known as frequency of the sound wave. S.I Unit of frequency is Hertz (Hz).
  • Amplitude – The magnitude of the maximum disturbance in the medium on either side of the mean value is called the amplitude of the wave. It is usually denoted by the letter A.
  • Speed – The speed of sound is defined as the distance which a point on a wave, such as a compression or rarefaction, travels per unit time.
  •  When an object vibrates, it sets the particles of the medium around it vibrating. The particles do not travel all the way from the vibrating object to the ear. The particles in the medium in contact with the vibrating object displace from its equilibrium position. It then exerts force on the adjacent particles. After displacing the adjacent particle the first particle of medium comes back in its original position. This process continues in the medium till the sound reaches your ear.  
  • When a vibrating object moves forward, it pushes and compresses the air in front of it creating a region of high pressure , this region is called a compression.
  • When a vibrating object moves backwards. It creates a region of low pressure is called rarefaction.
  • He region of high pressure is called compression and the region of low pressure is called rarefaction.
  • Sound propagates in the medium as a series of compressions and rarefactions.
  • The individual particles of the medium moves in a direction parallel to the direction of propagation of the disturbance. The particles do not move from one place to another but they simply oscillate back and forth their position of rest. This is exactly how a sound wave propagates; hence sound waves are longitudinal waves.
  • The wave particles do not oscillate along the line of wave propagation but oscillate up and down about their mean position as the wave travels, such the wave is called transverse wave.   
  • The loudness or softness of a sound is determined basically by its amplitude. The amplitude of the sound wave depends upon the force with which an object is made to vibrate.
  • most common medium through which sound travels is Air.
  • Soft sound has small amplitude and louder sound has large amplitude. Soft sound is produced by less energy while louder sound is produced by more energy.
  • Tone is known  as sound of single frequency.
  • Note is known as sound of a mixture of several frequencies.
  • The time taken by a pendulum to complete one oscillation is called its time period. 
  •  The distance between two consecutive compressions or two consecutive rarefaction is called the wavelength.
  • How the brain interprets the frequency of an emitted sound is called the pitch.
  •  The different between transverse wave and longitudinal wave.

 

transverse wave

longitudinal wave

1.Particles of the medium moves in a direction parallel to the direction of propagation of the disturbance.

 

2.It forms compression and rarefaction.

3.Example – light wave. 

1.Particles do not oscillate along the line of wave propagation but oscillate up and down about their mean position as the wave travels

2.It forms crest and trough.

3.Example – sound wave.

12. Sound

Additional -Questions

Class 9 Science English Updated : 06 March 2026

 

12. Sound

Exercise NCERT Book

Class 9 Science English Updated : 06 March 2026

 LESSON – 12

Que. – How is sound Produced?
Ans. – Sound is produced by Vibrating objects. 
Que. – What is Medium?
Ans. – The matter or substance through which sound is transmitted is called a medium?
Que. – In Which Medium Sound transmits fast?
       (a)   solid   (b)   liquid      (c)   gas   
Ans. – Solid. 
Que. – Explain how sound is produced by your school bell?
Ans. – school bell is made of metal. When a wooden hammer is stroked on it the metal produces vibrations, which causes sound. 
Que. – Why are sound waves called the mechanical waves?
Ans. – for propagation of sound it need a material medium like air, water and steel etc. Sound can be visualized as a wave. It is characterized by physical motion of particles in the medium. When a sound passes through a medium, the medium shows its physical motion and vibrates. So the sound waves are called the mechanical waves. 
Que. – Write the characteristics of a sound wave.
Ans. – sound wave is described by its
1. Frequency – The number of oscillations completed by sound wave in per unit time is known as frequency of the sound wave. S.I Unit of frequency is Hertz (Hz) 
2. Amplitude – The magnitude of the maximum disturbance in the medium on either side of the mean value is called the amplitude of the wave. It is usually denoted by the letter A. 
3. Speed – The speed of sound is defined as the distance which a point on a wave, such as a compression or rarefaction, travels per unit time. 
Que. – How does the sound produced by a vibrating object in a medium reach to our ears? 
                                       
Ans. - When an object vibrates, it sets the particles of the medium around it vibrating. The particles do not travel all the way from the vibrating object to the ear. The particles in the medium in contact with the vibrating object displace from its equilibrium position. It then exerts force on the adjacent particles. After displacing the adjacent particle the first particle of medium comes back in its original position. This process continues in the medium till the sound reaches your ear.   
Que. – What is compression?
Ans. – When a vibrating object moves forward, it pushes and compresses the air in front of it creating a region of high pressure, this region is called a compression. 
Que. – What is rarefaction? 
Ans. – When a vibrating object moves backwards. It creates a region of low pressure is called rarefaction. 
Que. – What are called the regions of high pressure and low pressure in sound wave?
Ans. - The region of high pressure is called compression and the region of low pressure is called rarefaction. 
Que. – In which form sound propagates in any medium?
Ans. – Sound propagates in the medium as a series of compressions and rarefactions. 
Que. – Sound waves are longitudinal waves. Why?
Ans. – The individual particles of the medium moves in a direction parallel to the direction of propagation of the disturbance. The particles do not move from one place to another but they simply oscillate back and forth their position of rest. This is exactly how a sound wave propagates; hence sound waves are longitudinal waves. 
Que. – What is transverse wave?
Ans. – The wave particles do not oscillate along the line of wave propagation but oscillate up and down about their mean position as the wave travels, such the wave is called transverse wave.   
Que. – Which wave property determines (a) loudness (b) pitch?
Ans. – The loudness or softness of a sound is determined basically by its amplitude. The amplitude of the sound wave depends upon the force with which an object is made to vibrate. 
             While, the pitch of sound is determined by its frequency. If the frequency is increased the pitch also raises. 
Que. – Write the name of most common medium through which sound travels. 
Ans. – Air.
Que. – Write the difference between soft and louder sound.
Ans. – Soft sound has small amplitude and louder sound has large amplitude. Soft sound is produced by less energy while louder sound is produced by more energy. 
Que. – What is called a sound of single frequency? 
Ans. – Tone 
Que. – What is called a sound of a mixture of several frequencies? 
Ans. – Note 
Que. – Define time period.
Ans – The time taken by a pendulum to complete one oscillation is called its time period.  
Que. – What is the wavelength?
Ans. – The distance between two consecutive compressions or two consecutive rarefactions is called the wavelength.
           The wavelength is denoted by Greece word (λ)
           Speed of sound = wavelength × frequency
Que. – What is the pitch of sound. 
Ans. – How the brain interprets the frequency of an emitted sound is called the pitch. 
Que. – Write the different between transverse wave and longitudinal wave. 
Ans. – The different between transverse wave and longitudinal wave.
transverse wave
1. Particles of the medium moves in a direction parallel to the direction of propagation of the disturbance. 
2. It forms compression and rarefaction.
3. Example – light wave. 
longitudinal wave
1. Particles do not oscillate along the line of wave propagation but oscillate up and down about their mean position as the wave travels
2. It forms crest and trough. 
3. Example – sound wave. 

12. Sound

Additional -Questions 3

Class 9 Science English Updated : 06 March 2026

   LESSON – 12

Que. – How is sound Produced?
Ans. – Sound is produced by Vibrating objects. 
Que. – What is Medium?
Ans. – The matter or substance through which sound is transmitted is called a medium?
Que. – In Which Medium Sound transmits fast?
       (a)   solid   (b)   liquid      (c)   gas   
Ans. – Solid. 
Que. – Explain how sound is produced by your school bell?
Ans. – school bell is made of metal. When a wooden hammer is stroked on it the metal produces vibrations, which causes sound. 
Que. – Why are sound waves called the mechanical waves?
Ans. – for propagation of sound it need a material medium like air, water and steel etc. Sound can be visualized as a wave. It is characterized by physical motion of particles in the medium. When a sound passes through a medium, the medium shows its physical motion and vibrates. So the sound waves are called the mechanical waves. 
Que. – Write the characteristics of a sound wave.
Ans. – sound wave is described by its
1. Frequency – The number of oscillations completed by sound wave in per unit time is known as frequency of the sound wave. S.I Unit of frequency is Hertz (Hz) 
2. Amplitude – The magnitude of the maximum disturbance in the medium on either side of the mean value is called the amplitude of the wave. It is usually denoted by the letter A. 
3. Speed – The speed of sound is defined as the distance which a point on a wave, such as a compression or rarefaction, travels per unit time. 
Que. – How does the sound produced by a vibrating object in a medium reach to our ears?                   
Ans. - When an object vibrates, it sets the particles of the medium around it vibrating. The particles do not travel all the way from the vibrating object to the ear. The particles in the medium in contact with the vibrating object displace from its equilibrium position. It then exerts force on the adjacent particles. After displacing the adjacent particle the first particle of medium comes back in its original position. This process continues in the medium till the sound reaches your ear.   
Que. – What is compression?
Ans. – When a vibrating object moves forward, it pushes and compresses the air in front of it creating a region of high pressure, this region is called a compression. 
Que. – What is rarefaction? 
Ans. – When a vibrating object moves backwards. It creates a region of low pressure is called rarefaction. 
Que. – What are called the regions of high pressure and low pressure in sound wave?
Ans. - The region of high pressure is called compression and the region of low pressure is called rarefaction. 
Que. – In which form sound propagates in any medium?
Ans. – Sound propagates in the medium as a series of compressions and rarefactions. 
Que. – Sound waves are longitudinal waves. Why?
Ans. – The individual particles of the medium moves in a direction parallel to the direction of propagation of the disturbance. The particles do not move from one place to another but they simply oscillate back and forth their position of rest. This is exactly how a sound wave propagates; hence sound waves are longitudinal waves. 
Que. – What is transverse wave?
Ans. – The wave particles do not oscillate along the line of wave propagation but oscillate up and down about their mean position as the wave travels, such the wave is called transverse wave.   
Que. – Which wave property determines (a) loudness (b) pitch?
Ans. – The loudness or softness of a sound is determined basically by its amplitude. The amplitude of the sound wave depends upon the force with which an object is made to vibrate. 
             While, the pitch of sound is determined by its frequency. If the frequency is increased the pitch also raises. 
Que. – Write the name of most common medium through which sound travels. 
Ans. – Air.
Que. – Write the difference between soft and louder sound.
Ans. – Soft sound has small amplitude and louder sound has large amplitude. Soft sound is produced by less energy while louder sound is produced by more energy. 
Que. – What is called a sound of single frequency? 
Ans. – Tone 
Que. – What is called a sound of a mixture of several frequencies? 
Ans. – Note 
Que. – Define time period.
Ans – The time taken by a pendulum to complete one oscillation is called its time period.  
Que. – What is the wavelength?
Ans. – The distance between two consecutive compressions or two consecutive rarefactions is called the wavelength.
           The wavelength is denoted by Greece word (λ)
           Speed of sound = wavelength × frequency
Que. – What is the pitch of sound. 
Ans. – How the brain interprets the frequency of an emitted sound is called the pitch. 
Que. – Write the different between transverse wave and longitudinal wave. 
Ans. – The different between transverse wave and longitudinal wave.
transverse wave
1. Particles of the medium moves in a direction parallel to the direction of propagation of the disturbance. 
2. It forms compression and rarefaction.
3. Example – light wave. 
longitudinal wave
1. Particles do not oscillate along the line of wave propagation but oscillate up and down about their mean position as the wave travels
2. It forms crest and trough. 
3. Example – sound wave. 
📘

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