A source emits sound of frequency $f_s = 500\ \text{Hz}$ and moves directly towards a stationary observer with a speed of $30\ \text{m s}^{-1}$. At the same time the observer walks directly away from the source with a speed of $10\ \text{m s}^{-1}$. The speed of sound in air is $v = 340\ \text{m s}^{-1}$.

(a) Calculate the frequency heard by the observer.

(b) A second stationary source emits a sound of frequency $520\ \text{Hz}$. Determine the beat frequency heard by the observer due to the interference of the two sounds.

Question

A source emits sound of frequency $f_s = 500\ \text{Hz}$ and moves directly towards a stationary observer with a speed of $30\ \text{m s}^{-1}$. At the same time the observer walks directly away from the source with a speed of $10\ \text{m s}^{-1}$. The speed of sound in air is $v = 340\ \text{m s}^{-1}$.

(a) Calculate the frequency heard by the observer.

(b) A second stationary source emits a sound of frequency $520\ \text{Hz}$. Determine the beat frequency heard by the observer due to the interference of the two sounds.

Accepted Answer

Observed frequency ≈ 532 Hz, beat frequency = 12 Hz

Neco Model Questions Vol1 2023 Physics Question 17

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