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Sources and Properties of Sound

Different sounds are heared when the sound waves travel through a medium and reach our ears. There are different natural and artificial sources of sounds. Rustling leaves produces pleasant sound, whereas car horns makes unpleasant sound. In this concept, the students will understand how is sound produced and how it travels.

After reading the concept, students will be able to:

  • Explain what is sound.
  • Categorise man-made and natural sources of sound.
  • Describe different properties of sound.
  • Compare vibrations and pitch of sound.
  • Discus how do humans produce sounds.
  • Recite the importance of larynx, speech box and vocal cords in producing the sounds.

Each concept is explained to class 4 students using descriptions, illustrations, and concept maps. After you go through a concept, assess your learning by solving the two printable worksheets given at the end of the page.

Download the worksheets and check your answers with the worksheet solutions for the concept Sources and Properties of Sound provided in PDF format.

What is Sound?

A sound is a form of energy that travels in waves through solid, liquid and gaseous media. The phenomenon of sound waves travelling through any medium is almost similar to the ripples on a water surface after a small rock is tossed in a waterbody.

What is sound waves
Ripples in water


How is sound produced?

  • Sounds are created when an object vibrates, and as a result, the air surrounding the object also starts to vibrate. This is how sound reaches our ear through the waves of vibrations.
  • Vibrations are usually caused by the rapid back and forth movement of the object’s molecules. Similarly, the air molecules surrounding the object also show such rapid movements.
How is sound produced short answer


Sound vibration patterns


Sources of aound:

Sources of sound can be divided into two types—

1. Natural Sources of Sound:

These sources can produce sound naturally.


Natural Sources of Sound examples

Human talking

Natural Sources of Sound

Rustling of leaves

Natural Sources of Sound

Thunder booming

Natural Sources of Sound

Bird’s chirping

2. Man-made/Artificial sources of sound:

These are sources of sounds that man artificially makes.


Types of artificial sounds
Types of artificial sounds
Air horn
Types of artificial sounds
Types of artificial sounds
Flute’s sound


Pleasant and unpleasant sounds:

Sounds that make us feel happy and are pleasing to our ears are called pleasant sounds, whereas sounds that are uncomfortable to hear, cause irritation and may lead to temporary hearing impairment when heard continuously for a long time are called unpleasant sounds.

Pleasant Sounds Unpleasant Sounds
Sounds of a flute Sounds of a hammer
Sounds of a piano Car horns and truck horns
Sounds of a violin Electrical generator sounds
Sounds of a guitar Gunshot sounds


How Do Humans Produce Sounds?

  • There are specific components in our body that help us make sounds.
  • The larynx, also called the speech box, generates sound.
  • The larynx is situated at the top of the windpipe in our throat.
  • There are two ligaments in the larynx, called the vocal cords.
  • Stretching of vocal cords allows us to make sounds.
  • The vocal cords are connected to muscles that change the stretching of the cords. The muscles also change the space between the cords.
  • Air is passed between the two vocal cords with the help of the lungs.
  • As a result, the vocal cords start vibrating, thereby producing sound.
  • The sounds are made by the vibration of the vocal cords caused by the expelled air.
  • When the vocal cords are stretched, we make high sounds, and when the cords are relaxed, we make low sounds. This is known as the pitch of the sound.
How Do Humans Produce Sounds
How Do Humans Produce Sounds


Properties of Sound:

Amplitude and Pitch:

  • Amplitude measures the loudness or quietness of a sound.
  • Pitch denotes how high or how low a sound is.
what is pitch of sound
  • A high pitch sound has more vibrations, but a low pitch sound has fewer vibrations.
High and low pitch instruments
High and low pitch instruments


Interactions of sound with objects:

Sound waves can interact with objects in the following ways—

1. Reflection:

  • When sound waves strike a surface and then bounce off, it is called a reflection of sound.
What is reflection of sound

Examples: A very common example of the reflection of sound is the occurrence of echo. It is nothing but the repetition of sound caused due to the reflection of the sound waves.

2. Absorption:

  • When sound waves get absorbed, instead of getting reflected by a sound-absorbing material, it is called absorption of sound.

Examples: Sound absorbing materials are installed in cinema halls, auditoriums, etc. so that the loud noise created in that space is not heard from outside.


New Words:

Hearing Impairment: The inability of a person to hear sounds properly.

Ligament: It is a band of tissue that holds bones and organs in their proper locations.


Did You Know?

  • The sound of an approaching train can be heard if we put our ears to the railway tracks that are made of steel. It happens because sound travels faster in a solid medium than in a gaseous medium.
  • Unlike light, sound cannot travel through a vaccuum. It needs a medium (solid, liquid or gas) to travel.
  • Animals with large ears can hear better than animals with small ears.
Sound of an approaching train through tracks and steps
Properties and sources of sound
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