##### Physics
General Knowledge

# Sound Wave

## Sound Wave

Sound waves are longitudinal mechanical waves.
According to their frequency range, longitudinal mechanical waves are divided into the following categories :
1. Audible or Sound Waves
2. Infrasonic Waves
3. Ultrasonic Waves

## 1. Audible or Sound Waves

The longitudinal mechanical waves which lie in the frequency range 20 Hz to 20000 Hz are called audible or sound waves. These waves are sensitive to human ear. These are generated by the vibrating bodies such as tuning fork, vocal cords etc.

## 3. Ultrasonic Waves

The longitudinal mechanical waves having frequencies greater than 20000 Hz are called ultrasonic waves. Human ear can not detect these waves. But certain creatures like dog, cat, bat, mosquito can detect these waves. Bat not only detect but also produce ultrasonic.
Ultrasonic waves can be produced by Galton's whistle or Hartman's generator or by the high frequency vibrations of a quartz crystal under an alternating electric field (Piezo - electric effect) or by the vibrations of a ferromagnetic rod under an alternating magnetic field.

## Applications of Ultrasonic Waves

1. For sending signals.
2. For measuring the depth of sea.
3. For cleaning cloths, aeroplanes and machinery parts of clocks.
4. For removing lamp-shoot from the chimney of factories.
5. In sterilizing of a liquid.
6. In Ultrasonography.

## Speed of Sound

»   Speed of sound is different in different mediums. In a medium, the speed of sound basically depends upon elasticity and density of medium.
»   Speed of sound is maximum in solids and minimum in gases.
»   When sound enters from one medium to another medium, its speed and wavelength Changes but frequency remains unchanged.
»   In a medium, the speed of sound is independent of frequency. Effect of pressure on speed of sound: The speed of sound is independent of pressure i.e. speed remains unchanged by the increase or decrease of pressure.

»   Effect of presser on speed of sound : The speed of sound is independent of presser i.e. speed remain unchanged by increase or decrees of presser.

»   Effect of Temperature on speed of sound :The speed of Bound Increase with, increase of temperature of the medium. The speed of sound In air Increase by the 0.61 m/s when the temperature is increased by 1°C.

»   Effect of humidity on speed of sound :The speed of sound is more in humid air then in dry air because the density of humid air is less than the density of dry air