The figure below shows the apparatus set up to investigate the interference of sound wave.
Two distanced speakers are connected to the same audio generator.
A microphone is moved in front of the 2 speakers from left to right.

Result:
Alternating loud and soft sounds are detected as the microphone is moved from left to right.

Formula

The wavelength of the sound wave is given by the equation

a = Distance between two loudspeakers
x = Distance between two successive loud sound.
D = Distance between the straight-line path and the two loudspeakers.

Q & A

Explain briefly why alternating loud and soft sound is detected in front of the speakers?

The alternating loud and soft sounds are caused by interference of the sound wave.
The loud sound corresponds to the occurrence of constructive interference.
The soft sound corresponds to the occurrence of destructive interference.

Q & A

Explain why the experiment is not suitable to be done in a lab.

The sound wave will be reflected by the wall and causes interference of reflected waves.

Q & A

How do we make sure that the sources of the sound wave are coherent?

The two loudspeakers are sources of two coherent sound waves as they are connected to the same audio signal generator.

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