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Chapter 13 – Sound

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


We all hear different types of sounds like the chirping of a bird, the noise of vehicles, music, the sounds of working machines. Some of these sounds are pleasant, while some sounds are intolerable. Why do we hear these sounds? How does the sound travel? Up to which level we could listen to these sounds?

These are some questions that come to our mind when we think about “sound“? 

When anything vibrates, it creates sound waves. The loudness of sound depends on the intensity of vibration of the object.. Vibration is the to-and-fro motion of an object. Various activities cause vibration, such as striking, stretching, rubbing, blowing, shaking, rotating, scratching, etc.

  • Vibration in the object causes a sound.
  • It is the form of mechanical energy.
  • Sound needs a medium for propagation. The medium could be any solid, liquid, or gas. Air is the common medium through which the sound travels.
  • The sound wave is a longitudinal wave. It means when there is vibration in the molecules, they transfer energy to each-other and move in the direction of the vibration.
  • Low pitch sound and high pitch sound have low frequency and high frequency, respectively.

(Frequency, v = 1/T, is defined as the number of completed oscillations per unit time)

(Longitudinal waves: Here, the particle moves in the same direction of wave propagation.)

Factors that affect the nature of propagation of the sound:

  • Density and pressure
  • The medium through which sound waves travels

In humans, the vibrations are produced by vocal cords. The vocal cord is attached with muscles, which changes the expansion in the cords, and sound is produced. 

We Hear Sound Through Our Ears

The ear converts variations in pressure (in the air) having audible frequency range into electrical signals. These frequencies are transmitted to the brain via the auditory nerve.

  • Outer ear: This is known as Pinna which gathers sound from the surrounding. Here, due to compression in the medium, the eardrum starts vibrating which is in the auditory canal.
  • Middle ear: Here, vibrations are amplified by three bones, i.e., hammer, anvil, and stirrup.
  • Inner ear: Here, the cochlea converts the variations in pressure into electrical signals. These electrical signals are further transmitted to the brain using the auditory nerve. The brain decodes them as sound.
  • Audible sound: The frequency range which we can hear is called audible sound. It may vary for each living being. Audible sound ranges from 20Hz to 20kHz in human beings.
  • Inaudible sound: The sound frequency which cannot be heard is called inaudible sound. 

Our ears can detect the sound frequency between 20Hz to 20kHz. Sound waves below or above this range are inaudible to the human ear. Dogs can hear sounds above 20kHz.

Noise and Music

Let’s see the differences between noise and music:

A sound pleasant to hearUnwanted and unpleasant sound waves.
It causes mental peace and relaxationIt causes disturbance
Music has a positive effect on healthNoise harms health
The sources are musical instrumentsThe sources can be vehicles, machines, etc.

Noise pollution is unwanted and disturbing sound waves in the environment.

Main sources of noise pollution are:

  • Vehicles
  • Heavy machines
  • Bursting of crackers
  • Loudspeakers
  • Loud sounds of musical instruments

Harmful effects of noise pollution:

  • Noise harms our ears and reduces our listening capability.
  • It can distract people from their work and study.
  • Causes headache and irritation.

Sound travels from source to listener via any medium. A medium can be solid, liquid, and gas because these can carry sound waves from one place to another.

Try this activity:

Apparatus use – Electric bell, bell jar, vacuum pump

Procedure –

(i) Keep an electric bell inside the bell jar.

(ii) Start releasing air from the closed bell jar. You will be able to hear the reducing sound of an electric bell from the bell jar. After some time, no sound will be heard from the bell jar.

This experiment shows that in the presence of air, we can hear the sound but in a vacuum, we cannot.

  • Vibration: Vibration is the repetitive to and fro motion of the object.
  • Amplitude: Amplitude is the maximum extent of vibration of the vibrating object from its middle position.
  • Time period (T): It is the time taken by the vibrating object to complete one vibration.
  • Frequency: Frequency is the number of vibrations in the unit time.
    v = 1/T
  1. What does sound mean?

Ans: Sound is mechanical energy that gives the sensation of hearing.

  1. What are the 3 types of sound?

Ans. 3 types of sound are – audible, infrasonic, and ultrasonic.

  1. What is the sound wave in physics?

Ans. The pattern of disturbance caused by the energy traveling away from the source is called sound waves. Sound waves are longitudinal waves.

  1. What are the types of sound waves?

Ans. 3 types of sound waves are mechanical waves, longitudinal waves, and pressure waves.

  1. Who invented sound?

Ans. Initially, da Vinci invented that sound travels in waves.

  1. What are the five characteristics of sound?

Ans: Characteristics of a sound:

  • Vibration in the object causes a sound.
  • It is mechanical energy.
  • It needs a medium to travel from source to listener.
  • The sound wave is a longitudinal wave.
  • Low pitch sound and high pitch sound have low frequency and high frequency, respectively.

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  • We hear sound because of vibrations in the object
  • Sound needs a medium to travel from source to listeners.
  • Every species of living beings can hear a specific range of frequency. Humans can hear 20Hz-20kHz range of frequency.
  • Sound cannot travel in vacuum (no medium). 
  • Sound is categorized into audible, infrasonic and ultrasonic.
  • Sound waves are longitudinal waves.
  • Amplitude, frequency and time period are the three main factors which influence the sound.
  • Noise pollution is the unwanted sounds that are present in the environment. It can have harmful effects on health.

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
  • Matter In Our Surroundings
  • Metallurgy
  • Metals And Non-Metals
  • 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
  • Reproductive Health
  • 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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