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Chapter 12 – Sound

The following Topics and Sub-Topics are covered in this chapter and are available on MSVgo:


Have you ever used a guitar, drum, or violin as a musical instrument? You hear a vibration as you touch the strings of a guitar. The same for a drum, we hear a ‘thump’ sound as we strike a drum. Indeed, how can one instrument produce a wide range of sounds? How does this occur? What is the sound? How do we create sound? How is sound produced and how is production and propagation of sound achieved? 

A sound, much like electricity, heat, or light, is a source of energy. Let’s analyze a few sound sources, including a whistle. It makes a loud ringing noise as you hit a button. Now, instead of just listening to the alarm, once you have reached it, put your finger on the bell. Are you able to feel it vibrating? It’s the secret to the sound here. For guitars and drums, it’s much more apparent. Any time you pluck it, you can see the wires vibrating. The echo often ceases when the bell or the guitar stops vibrating. Vibration is called the to and fro motion of the body.

Characteristics of Sound Wave 

A continuous succession of peaks and valleys is pictorially represented by tone. The difference is called the wavelength of the wave or the time between two successive peaks or troughs. The number of cycles per unit time is referred to as the tone frequency. Frequency is measured in per second or Hertz intervals. 

The more an entity vibrates, that is, the higher the frequency, the greater the sound pitch. The distinction between the voice of a man and that of a woman must be obvious to you. A man’s voice has a lower frequency that adds to the bass’s deepness in the voice. Men, on the other hand, have a higher-frequency sound that results in greater shrillness or pitch.

A sound wave’s speed is determined by the type of medium by which it passes. In solids, sound waves move the fastest regardless of the proximity of molecules. Similarly, in gases, sound waves propagate steadily when gases are spaced far away from each other. The condition of the medium through which sound passes is not the only aspect determining the velocity of a sound. The density, temperature, and elasticity of the medium in which sound waves pass will also influence the speed of a sound wave.

The sound that a guitar produces is different from the sound that a drum produces. This is because different characteristics are found in the sound produced by different sources. The pitch, wavelength, and amplitude will describe sound. 

Sound Frequency 

A sound wave frequency is defined as the number of rarefactions and compressions occurring per unit of time. The frequency formula for a wave is given as: 

f = 1/T

Sound Wavelength 

The distance is defined as the wavelength of a sound wave between the successive compression and rarefaction. The sound formula’s wavelength is given as follows: 

\lambda = v/F

Sound Amplitude 

In a sound wave, the sound amplitude is the frequency of the highest disturbance. A measure of energy is also the amplitude. The larger the amplitude, the greater the energy of a sound wave.

Sound Reflection 

Reflection of sound  is akin to the reflection of light. The reflection of sound complies with the following principles of reflection. 

  1. The incidence angle is equal to the angle of reflection. 
  2. The sound of the incident, the normal sound, and the normal sound lay all on the same plane. 

It is transmitted back to its origins as a sound strikes a rough surface. This sound reflection is otherwise known as an echo. Although soft surfaces absorb sound and quiet it, hard surfaces appear to reflect sound. If the sound wave is low in pitch, so the sound wave will not be reflected. Often, if the environment is wide and has several reflective surfaces, such as valleys and vast empty spaces, we hear multiple reflections from a sound source. This phenomena is referred to as reverberation. A principle in working of sonar.

Sounds ranging from 20 Hz to 20 kHz can be detected by human beings. Sounds of frequencies above the human hearing spectrum are referred to as ultrasound, and are widely used in sonar. Infrasound is the name of sounds with frequencies outside the human ear structure and working capacity. The typical sound produced by human speech has frequencies of between 100 and 1,000 H

This chapter taught us the basics of sound. We learned about the types, reflection and frequency of sound. We can use this knowledge and understand the infrasonic and ultrasonic waves and working of sonar.

1. What does sound mean? 

Mechanical radiant energy that is emitted in a material medium (such as air) by longitudinal pressure waves and is the objective source of hearing. 

2. What is sound class 9th? 

Sound is a form of energy that in our ears creates a sense of hearing . Due to the vibration of objects, sound is produced. 

3. What are the 5 characteristics of sound? 

Sound waves have five major characteristics: wavelength, amplitude, frequency, period of time, and velocity. 

4. What are 4 properties of sound? 

Pitch, intensity (loudness), duration, and timbre are the four properties of sound. 

5. What are the two key features of sound?

Frequency, velocity and amplitude are what they are. Pitch and loudness, two of the major sound features.

At MSVgo, we have created a vast library of video lessons to learn and understand the essential features of sound. Just download the app and see for yourself how easy it is to understand Math & Science concepts such as this one.

High School Physics

  • Alternating Current
  • Atoms
  • Communication Systems
  • Current Electricity
  • Dual nature of Radiation and Matter
  • Electric Charges and Fields
  • Electricity
  • Electromagnetic Induction
  • Electromagnetic Waves
  • Electron Beams and Radioactivity
  • Electrons and Photons
  • Electrostatic Potential and Capacitance
  • Fluid Pressure
  • Force and Acceleration
  • Force And Laws Of Motion
  • Gravitation
  • Internal Energy
  • Kinetic Theory
  • Law of motion
  • Light – Reflection And Refraction
  • Magnetic Effects Of Electric Current
  • Magnetism and Matter
  • Management Of Natural Resources
  • Mechanical properties of Fluids
  • Mechanical properties of Solids
  • Motion
  • Motion in a plane
  • Motion in a straight line
  • Moving Charges and Magnetism
  • Nuclear Energy
  • Nuclei
  • Oscillations
  • Our Environment
  • Paths of Heat
  • Physical world
  • Ray optics and optical instruments
  • Semiconductor Devices
  • Semiconductor Electronics: Materials, Devices and Simple Circuits
  • Simple Machines
  • Sound
  • Sources Of Energy
  • Specific and Latent Heats
  • Spherical Mirrors
  • Static Electricity
  • Systems of Particles and Rotational motion
  • Thermal properties of matter
  • Thermodynamics
  • Units and Measurement
  • Vectors, Scalar Quantities and Elementary Calculus
  • Wave Optics
  • Waves
  • Work, Power and Energy

High School Chemistry

  • Acids, Bases and Salts
  • Alcohols, Phenols and Ethers
  • Aldehydes, Ketones and Carboxylic Acids
  • Aliphatic and Aromatic Hydrocarbons
  • Alkyl and Aryl Halides
  • Amines
  • Analytical Chemistry 
  • Atomic Structure
  • Atoms And Molecules
  • Basic concepts of Chemistry
  • Biomolecules
  • Carbon And Its Compounds
  • Carboxylic acids and Acid Derivatives
  • Chemical Bonding and Molecular Structures
  • Chemical Energetics
  • Chemical Equilibria
  • Chemical Kinetics
  • Chemical Reactions And Equations
  • Chemical Reactions and Their Mechanisms
  • Chemistry in Everyday Life
  • Chemistry of p-Block elements
  • Chemistry of Transition and Inner Transition
  • Classification of Elements
  • Coordination Compounds
  • Cyanide, Isocyanide, Nitro compounds and Amines
  • Electrochemistry
  • Electrolysis
  • Elements, Compounds and Mixtures
  • Environmental Chemistry
  • Equilibrium
  • Ethers and Carbonyl compounds
  • Haloalkanes and Haloarenes
  • Hydrocarbons
  • Hydrogen
  • Ideal solutions
  • Introduction to Organic Chemistry
  • Ionic equilibria
  • Matter
  • Matter Around Us
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  • Metallurgy
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  • Mole Concept and Stoichiometry
  • Natural Resources
  • Organic Chemistry – Basic Principles
  • Periodic Classification of Elements
  • Physical and Chemical Changes
  • Physical and Chemical Properties of Water
  • Polymers
  • Preparation, Properties and Uses of Compounds
  • Principles and Processes of Isolation of Elements
  • Redox Reactions
  • Relative Molecular Mass and Mole
  • States of Matter
  • Structure Of The Atom
  • Study of Compounds
  • Study of Gas Laws
  • Study of Representative Elements
  • Surface Chemistry
  • The d-block and f-block elements
  • The Gaseous State
  • The p-Block Elements
  • The Periodic Table
  • The s-Block Elements
  • The Solid State
  • Thermodynamics

High School Biology

  • Absorption and Movement of Water in Plants
  • Adolescent Issues
  • Anatomy of Flowering Plants
  • Animal Kingdom
  • Bacteria and Fungi-Friends and Foe
  • Biodiversity and Conservation
  • Biofertilizers
  • Biological Classification
  • Biomedical Engineering
  • Biomolecules
  • Biotechnology and its Applications
  • Biotic Community
  • Body Fluids and Circulation
  • Breathing and Exchange of Gases
  • Cell – Unit of Life
  • Cell Cycle and Cell Division
  • Cell Division and Structure of Chromosomes
  • Cell Reproduction
  • Cellular Respiration
  • Chemical Coordination and Integration
  • Circulation
  • Control And Coordination
  • Crop Improvement
  • Digestion and Absorption
  • Diversity In Living Organisms
  • Ecosystem
  • Environmental Issues
  • Excretory Products and their Elimination
  • Flowering Plants
  • Genes and Chromosomes
  • Health and Diseases
  • Health and Its Significance
  • Heredity And Evolution
  • Heredity and Variation
  • How Do Organisms Reproduce?
  • Human Diseases
  • Human Eye And Colourful World
  • Human Health and Disease
  • Human Population
  • Human Reproduction
  • Hygiene
  • Improvement In Food Resources
  • Integumentary System- Skin
  • Kingdom Fungi
  • Kingdom Monera
  • Kingdom Protista
  • Life Processes
  • Locomotion and Movement
  • Microbes in Human Welfare
  • Mineral Nutrition
  • Molecular Basis of Inheritance
  • Morphology of Flowering Plants
  • Neural Control And Coordination
  • Nutrition in Human Beings
  • Organism and Population
  • Photosynthesis
  • Photosynthesis in Higher Plants
  • Plant Growth and Development
  • Plant Kingdom
  • Pollination and Fertilization
  • Pollution; Sources and its effects
  • Principles of Inheritance and Variation
  • Reproduction and Development in Angiosperms
  • Reproduction in Organisms
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  • Respiration in Human Beings
  • Respiration in Plants
  • Respiratory System
  • Sexual Reproduction in Flowering Plants
  • Strategies for Enhancement in Food Production
  • Structural Organisation in Animals
  • Structural Organisation of the Cell
  • The Endocrine System
  • The Fundamental Unit Of Life
  • The Living World
  • The Nervous System and Sense Organs
  • Tissues
  • Transpiration
  • Transport in Plants

High School Math

  • Algebra – Arithmatic Progressions
  • Algebra – Complex Numbers and Quadratic Equations
  • Algebra – Linear Inequalities
  • Algebra – Pair of Linear Equations in Two Variables
  • Algebra – Polynomials
  • Algebra – Principle of Mathematical Induction
  • Algebra – Quadratic Equations
  • Binomial Theorem
  • Calculus – Applications of Derivatives
  • Calculus – Applications of the Integrals
  • Calculus – Continuity and Differentiability
  • Calculus – Differential Equations
  • Calculus – Integrals
  • Geometry – Area
  • Geometry – Circles
  • Geometry – Conic Sections
  • Geometry – Constructions
  • Geometry – Introduction to Euclid’s Geometry
  • Geometry – Three-dimensional Geometry
  • Geometry – Lines and Angles
  • Geometry – Quadrilaterals
  • Geometry – Straight Lines
  • Geometry – Triangles
  • Linear Programming
  • Matrices and Determinants
  • Mensuration – Areas
  • Mensuration – Surface Areas and Volumes
  • Number Systems
  • Number Systems – Real Numbers
  • Permutations and Combinations
  • Probability
  • Sequence and Series
  • Sets and Functions
  • Statistics 
  • Trignometry – Height and Distance
  • Trignometry – Identities
  • Trignometry – Introduction

Middle School Science

  • Acids, Bases And Salts
  • Air and Its Constituents
  • Basic Biology
  • Body Movements
  • Carbon and Its Compounds
  • Cell – Structure And Functions
  • Changes Around Us
  • Chemical Effects Of Electric Current
  • Chemistry in Your Life
  • Coal And Petroleum
  • Combustion And Flame
  • Components Of Food
  • Conservation Of Plants And Animals
  • Crop Production And Management
  • Electric Current And Its Effects
  • Electricity And Circuits
  • Elements and Compounds
  • Fibre To Fabric
  • Food production and management
  • Force And Pressure
  • Forests: Our Lifeline
  • Friction
  • Fun With Magnets
  • Garbage In, Garbage Out
  • Getting To Know Plants
  • Health and Hygiene
  • Heat
  • Hydrogen
  • Life Processes: Nutrition in Animals and Plants
  • Light, Shadows And Reflections
  • Materials: Metals And Non-Metals
  • Matter and Its States
  • Metals and Non-metals
  • Micro Organisms: Friend And Foe
  • Motion And Measurement Of Distances
  • Motion And Time
  • Nutrition In Animals
  • Nutrition In Plants
  • Organization in Living Things
  • Our Environment
  • Physical And Chemical Changes
  • Pollution and conservation
  • Pollution Of Air And Water
  • Reaching The Age Of Adolescence
  • Reproduction In Animals
  • Reproduction In Plants
  • Respiration In Organisms
  • Rocks and Minerals
  • Separation Of Substances
  • Simple Machines
  • Soil
  • Some Natural Phenomena
  • Sorting Materials Into Groups
  • Sound
  • Stars And The Solar System
  • Structure of Atom
  • Synthetic Fibers And Plastics
  • The Living Organisms And Their Surroundings
  • Transfer of Heat
  • Transformation of Substances
  • Transportation In Animals And Plants
  • Universe
  • Waste-water Story
  • Water: A Precious Resource
  • Weather, Climate And Adaptations Of Animals To Climate
  • Winds, Storms And Cyclones

Middle School Math

  • Addition
  • Area and Its Boundary
  • Boxes and Sketches
  • Data Handling
  • Fun With Numbers
  • Heavy and Light
  • How Many
  • Long And Short
  • Mapping
  • Measurement
  • Money
  • Multiplication and Factors
  • Multiply and Divide
  • Numbers
  • Parts and Wholes
  • Pattern Recognition
  • Patterns
  • Play With Patterns
  • Rupees And Paise
  • Shapes And Angles
  • Shapes And Designs
  • Shapes and Space
  • Similarity
  • Smart Charts
  • Squares
  • Subtraction
  • Tables And Shares
  • Tenths and Hundredths
  • Time
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