Question
Answers

How is speed of sound in air affected by pressure of air?
A. No effect
B. Decreases with increases in pressure
C. Increases with increases in pressure
D. Data insufficient

Answer
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Hint: Sound travels at a speed of 330 meter per second in air. Vibrations caused by the source create a disturbance in the molecules in the medium which leads to the motion of sound. Air pressure is due to the interaction between walls and the molecules and not between molecules themselves.

Complete answer:
Sound travels in a medium due to the motion of the particles of the medium from the source to the listener. In an ideal gas approximation, air pressure has no role to play in deciding the speed of sound because pressure and density both contribute to the velocity of sound equally and thus cancels each other out.

Hence, Air pressure has no effect on sound speed.
So, the correct answer is “Option A”.

Additional Information:
Loudness of the sound is defined as the amplitude or intensity of a sound. The larger the amplitude of the sound wave, higher is its intensity and louder is the sound produced by that sound wave. The unit to measure the loudness of sound is called decibels (dB). Sound with very high amplitude can damage your ears but the ones with very low amplitude are difficult to hear.

We can hear only those sounds which have frequency from 20 Hz to 20 kHz. Our ear is not sensitive to frequencies higher or lower than the given range of frequencies. Higher the frequency of the sound, shriller is the sound and higher is the pitch. For example, the female voice has a higher pitch than male voice. Singing birds produce sound of high frequencies and high pitch.

Note:
Sound is different from noise in the sense that noise doesn’t have a well-defined frequency, amplitude, loudness or pitch. Noise is basically an incoherent mixture of sounds of different frequencies and loudness.