Sound Frequency | MCQs

Explanation

The human hearing range is typically from 20 Hz to 20,000 Hz.

Sounds below 20 Hz are called infrasound.

Sounds above 20,000 Hz are called ultrasound, both of which are inaudible to humans.

Since 22,000 Hz is above 20,000 Hz, it is an inaudible sound.

Explanation

Pitch determines whether a sound is shrill (high-pitched) or grave (low-pitched).

It depends on the frequency of the sound waves — higher frequency means higher pitch.

Explanation

When Bilal moves away from a stationary organ producing a sound of frequency 'f' with a speed equal to 0.5 times the speed of sound, he will hear a sound of lower frequency.

This phenomenon is known as the Doppler effect.

To calculate the frequency of the sound Bilal hears, we can use the following formula:

f' = f * (v + vL) / (v + vS)

Where:

- f' is the frequency of the sound heard by Bilal

- f is the frequency of the sound produced by the stationary organ

- v is the speed of sound

- vL is the speed of Bilal

- vS is the speed of the source (in this case, the stationary organ)

Since Bilal is moving away from the source, vS is negative.

We substitute the values into the formula:

f' = f * (v - 0.5v) / (v - (-v))

Simplifying the equation:

f' = f * (0.5v) / (2v)

f' = f * 0.5 / 2

f' = f * 0.25