Learn Class 9 Science - Sound

The term sound refers to the form of energy that makes the sensation in our ears. Or it is a type of vibration that gets moulded in our ears. When a single object vibrates, the object will make some movements in the present surrounding environment. Such types of molecules make them vibrant.

Types of sound

When we see the different types of sound, then these are mainly classified into the given terms.

1. Infrasonic sound

• The infrasonic sound is a type of sound with a frequency of less than 20 Hz.
• Example: The elephants use the sound of infrasonic to hear the sound of other crowds.

2. Sonic sound

• The sonic sound is present with a difference of frequency that varies from 20 - 20000 Hz.

3. Ultrasonic sound

• The ultrasound frequency varies from the frequency,i.e., more than 20000 Hz.

Properties of sound

The sound also has some properties. These properties are discussed here below:

• Frequency
• Amplitude
• Waveform
• Duration
• Timbre
• Velocity
• Wavelength
• Phase
• Envelope

Waves of sound

Generally, there are two waves of sound. These are as follows:

• Longitudinal waves

  These are the types of waves in which the particle will move back and front in the same direction.

• Transverse waves

  These are the waves in which the particles will move up & down, making a right angle with the direction.