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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