Chapter 11: Sound is part of the NCERT Class 9 Science textbook prescribed by the
Central Board of Secondary Education (CBSE).
In this chapter, we study how sound is produced by vibrating objects, how it propagates through different media,
how sound waves are described using physical quantities, and how these ideas are applied in daily life and technology.
This page is a chapter resource hub. It helps you plan your study,
understand the syllabus clearly, and access all learning, practice, and revision resources
related to Sound – Class 9 Science in one place.
The content and scope of this page are strictly based on NCERT Chapter 11 – Sound.
What You Will Learn in This Chapter
In this chapter, we develop the idea of sound as a mechanical wave that requires a material medium
for propagation.
As we proceed step by step, we learn how sound behaves in air, liquids, and solids, and how we describe sound using
measurable physical quantities.
Production of sound due to vibration of objects
Propagation of sound through a material medium
Sound as a longitudinal wave
Compressions and rarefactions in a sound wave
Characteristics of a sound wave:
Wavelength ($\lambda$)
Frequency ($\nu$)
Amplitude ($A$)
Speed of sound ($v$)
Relation between speed, wavelength, and frequency
Wave Equation
$$
v = \lambda \nu
$$
Pitch, loudness, intensity, and quality (timbre) of sound
Speed of sound in different media and effect of temperature
Reflection of sound
Echo and conditions for hearing an echo
Reverberation and its reduction
Range of hearing in humans
Infrasound and ultrasound
Applications of ultrasound in medicine and industry
👉 Each major concept will also have a dedicated Mind Map page to help you revise definitions,
formulas, diagrams, and key points at a glance.
CBSE Syllabus Coverage (Sound – Class 9)
As per the CBSE Class 9 Science syllabus, this chapter includes:
Nature of sound and its propagation in various media
Speed of sound
Range of hearing in humans
Ultrasound
Reflection of sound and echo
All topics listed above are fully covered in NCERT Chapter 11 and are reflected in the resources
linked on this page.
How to Study This Chapter (Recommended Approach)
We should study this chapter in a concept → practice → revision → assessment sequence.
1. Start with Notes
Begin with detailed notes to understand:
How sound is produced
How compressions and rarefactions are formed
Why sound waves are longitudinal
Use diagrams of tuning fork experiments and slinky models carefully.
Sound propagates as longitudinal waves in a material medium.
It propagates as compressions and rarefactions
Speed of sound depends on medium and temperature
Pitch depends on frequency
Loudness depends on amplitude
Ultrasound has important medical and industrial applications
Use this page as your starting point and navigation guide.
Begin with notes, revise using mind maps, practise numericals and questions,
and finally assess yourself using tests.
