# Sound

## 03 Characteristics of a Sound Wave

A sound wave can be described completely by its five characteristics:

• Wavelength
• Amplitude
• Time-period
• Frequency
• Velocity (or Speed)

#### WAVELENGTH

• Wavelength is the minimum distance in which a sound wave repeats itself.
• The SI unit for measuring wavelength is metre (m).

#### AMPLITUDE (A)

Amplitude of the wave is the magnitude of the maximum disturbance in the medium on either side of the mean value

#### TIME-PERIOD (T)

• The time required to produce one complete wave (or cycle) is called time-period of the wave.
• The time taken for one complete oscillation is called the time period of the sound wave.
• Its SI unit is second (s).

#### FREQUENCY

• The number of complete waves (or cycles) produced in one second is called frequency of the wave.
• The number of such oscillations per unit time is the frequency of the sound wave.
• The SI unit of frequency is hertz (which is written Hz).
• The frequency of a wave is the reciprocal of its time-period.

• The faster an object vibrates, i.e. the higher the frequency, the higher the pitch of the sound.

#### WHY IS MALE AND FEMALE VOICE DISTINCTIVE?

The difference between a male’s voice and female’s is because the voice of a male has a lower frequency which contributes to the deepness or the bass in the voice. Female, in contrast, has a voice with higher frequency resulting in a higher shrillness or pitch.

#### RELATIONSHIP BETWEEN VELOCITY, FREQUENCY AND WAVELENGTH OF A WAVE

The speed of sound is defined as the distance which a point on a wave, such as a compression or a rarefaction, travels per unit time.
We know that,

λ is the wavelength of the sound wave, which is the distance travelled by the sound wave. Then we get:

That is,    Speed / Velocity of wave  =  Frequency x Wavelength