Sounds that are pleasant to hear are called ultrasounds.

Communication in the submarines is using infra waves.

The device that transmits ultrasounds in SONAR is called _______.

• A receiver receives the sound reflected from the depths of the sea and perceives it. 

Sound cannot travel through _________.

Echo is _________ of the sound.

• Refraction is the bending of sound waves when they enter from one medium to another medium.

The reflection of sound in a closed surface is called _______.

• Amplification refers to the increase of the amplitude or loudness of sound.
• The repetition of a sound that is caused by the reflection of sound wave in large spaces is called an echo.

Which of the below is used to amplify sound?

Units to measure sound:

• The unit of power is watt.
• The unit of force is newton.
• The unit of work is Joule.

SONAR is used in _______

A sonar can detect the enemy ship using
_________ .

Distance can be measured in___________.

• The SI unit of time is Second.
• The SI unit of pressure is Pascal.
• The SI unit of force is Newton.

Music is heard from a vehicle's horn.

The SI unit of measurement of velocity is kg/s.

A guitar can produce __________.

Sound from a speaker undergoes an echo to reach the source back from a mountain located at a distance of 340 m from the source. The total time taken by the sound to cover this distance is 2 s. The speed of sound is ___ m/s.

After echo, the total distance travelled = 2d

Decreasing amplitude of a sound wave decreases the _______.