What is Range of Hearing of Human Beings

It is 20 Hz to 20000 Hz

However, children under age of 5 can hear upto 25000 Hz

 

Difference between Audible and Inaudible Sounds

Audible Sounds
Inaudible Sounds
Sounds which can be heard by us are called Audible Sounds
Sounds which we are not able to hear are called Inaudible Sounds
Range of Audible Frequency for Human ear is 20 Hz to 20000 Hz

It means human beings can hear sound having frequency from 20 Hz to 20000 Hz
Human beings cannot hear
Sound having frequency less than 20 Hz (Called Infrasonic or Infrasound)
Or
Having Frequency more than 20000 Hz (Called Ultrasonic or Ultrasounds)

 

Sounds - teachoo.jpg

 

What are Infrasonic Sounds

Sounds having frequency less than 20 Hz are called Infrasonic Sounds

Note

Human beings cannot hear infrasonic sounds

However some animals can communicate using infrasonic sound

Example-

Rhinoceros, whales and Elephants

 

Why do some animals get disturbed before earthquakes

Because earthquake produce low frequency sounds before main earthquake begins

These low frequency sounds alert these animals

 

What are Ultrasonic Sounds or Ultrasounds?

Frequency higher than 20000 Hz (20 kHz) are called Ultrasonic Sounds

it is produced by certain animals like Moths, bats, rats

 

Some animals such as dogs, bats and dolphins can hear ultrasounds

 

How does Bats use Ultrasound

Bats use ultrasound to navigate (move) and catch prey

Procedure

  • Bats produce high frequency ultrasonic squeaks
  • These squeaks reflect on prey and return back to bats ear
  • This gives bats idea of location of prey
  • Similarly,to find direction,bats use squeaks to find obstacles
  • These squeaks reflect on obstacle and return to bats ear
  • This helps bats to navigate (move)

 

Bats catching prey.png

 

How are moths able to escape attack of bats?

Some Moths have very sensitive ears

They are able to hear high frequency squeaks of bats

When they hear such squeaks

They change direction and are able to escape attack of bats

 

Questions

Question 1 Page 170 - What is the audible range of the average human ear?

View Answer

 

Question 2 Page 170 - "What is the range of frequencies associated with (a) Infrasound? (b) Ultrasound?"

View Answer

 

NCERT Question 14 - A sound wave travels at a speed of 339 m s–1. If its wavelength is 1.5 cm, what is the frequency of the wave? Will it be audible?

View Answer

 

NCERT Question 17 - Explain how bats use ultrasound to catch a prey.

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  1. Class 9
  2. Chapter 12 Class 9 - Sound

About the Author

Davneet Singh's photo - Teacher, Computer Engineer, Marketer
Davneet Singh
Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 9 years. He provides courses for Maths and Science at Teachoo.