Tag: study of sound

Sound is heard only if the body vibrates with a frequency of at least 20 Hz. Frequency of vibration of the pendulum is less than 20 Hz. Hence no sound is heard when the pendulum vibrates or oscillates in air.

The frequency of ultrasonic wave is greater than 20,000 Hz and equal to 107 Hz. These waves are not audible to a human ear but they can be heard by animals and birds.

Ultrasonic sounds are inaudible to humans, hence they are used for various purposes. These waves strike the object of interest and are reflected back. These reflected waves are captured and the object of interest is studied.

It will be audible by the human ear because vibration is produced 200 times/second.
So,frequency = 200 Hz
And the range of audible frequency is 20 Hz - 20,000 Hz.

Animals like dogs, whales, bats, dolphins, etc. can hear sounds of frequencies more than $20,000\ Hz$, i.e., ultrasounds. These sounds are inaudible to humans. However, they are important for these animals as it helps them to locate prey and escape from obstacles.

Has been seen that the behaviour of animals becomes unusual just before the tremor is felt. This is because animals are able to detect infrasonic waves produced at the time of tremor.
Infrasonic waves are waves of frequency less than 20Hz.

Bats can produce ultrasonic waves by flapping their wings.
They can also detect these waves.these waves produced by the bats after reflection from the obstacles like building guide them to  remain away from the obstacles during night with the help of ultrasonic waves.

A sound of frequency 50,000 hertz can be heard by a dog but not by a man. The waves having frequency between 20 Hz - 20,000 Hz are audible frequency of waves.

Infrasonic waves are waves whose frequency is below 20Hz. These sounds are not heard by human ears. Audible sounds are between 20 Hz and 20,000 Hz.

This is because the screams are ultrasonic(above 20,000 hertz) which human ear cannot hear.