Question

What is the frequency heard by a person driving at 15 m/s toward a blowing factory whistle (800. Hz) if the speed of sound is 340.6 m/s?

Answer 1

Answer:

The frequency heard by a person is 835.23 Hz.

Explanation:

Given that,

Frequency f = 800 Hz

Velocity $v_{r} =15\ m/s$

Speed of sound v = 340.6 m/s

We know that,

The frequency heard is

$f_{d} = f(\dfrac{v+v_{r}}{v-v_{s}})$

$f_{d}= 800(\dfrac{340.6+15}{340.6})$

$f_{d}=835.23 Hz$

Hence, The frequency heard by a person is 835.23 Hz.

Answer 2

Answer:

Frequency heard by the person = 835.23 Hz

Explanation:

Formula required:

Δf = f * (V/Vs)

Here,

Δf = Change in frequency.

V is the velocity of person driving.

Vs is the velocity of the sound (in air).

f is the frequency of the source (blowing whistle factory).

Frequency heard by the person = Frequency of source + change in frequency.

Note: Since the person is moving towards the source of sound, we need to add the frequencies.

Given details:

f = 800 Hz

V = 15 m/s

Vs = 340.6 m/s

Solution:

Δf = 800 * 15/340.6 = 35.23 Hz

Therefore,

Frequency heard by the person = 800 + 35.23 = 835.23 Hz