Tuesday, May 23, 2017

Here are some basic things you should know about Sound

The hearing limit of humans is 20 Hertz - 20000 Hertz. This means humans can only hear sound waves with frequency between 20cHz and 20000 Hz. The sounds with frequency below 20 Hz is called infrasonic sound. Elephants and whales use infrasonic sound waves for communication.

The sound with frequency above 20000 Hz is called ultrasonic sound. Galton's whistle is a whistle used for calling dogs. Galton's whistle emits ultrasonic sound.

Bats and dolphins use ultrasonic waves to find obstruction in their way and capture preys. This method of using sounds for finding obstructions in the path is called echo location.
SONAR is a device that uses ultrasonic sounds. SONAR is short for Sound Navigation and Ranging. SONAR is used for finding depth of oceans and position of fish denser areas.

Also for taking imagery of internal organs and embryo, ultrasonic sound waves are employed.


Frequency is the number of vibrations per second.


The unit of frequency is called Hertz.

When the amplitude of the vibration is increased, loudness is increased.


The unit of intensity of sound is called Decibel.

Hearing sounds above 90 dB continuously is damaging to the human ears. In residential areas the allowed limit of sound intensity is 50dB in the day time and 40 dB in the night time.