Hello to all the fantastic tutors! I'm stuck on this question, I was wondering if there is a way to solve this.
A car horn emits 378Hz sound. If the car moves at 23m/s with its horn blasting, what frequency will a person standing in front of the car hear?
What I've done:
f=378Hz
v=23m/s
wavelength: v/f = 23/378 = 0.061m
(not too sure what to do next)
Thank you so much in advance!
Fp = ((Vs+Vp)/(Vs-Vh))*Fh
Fp = ((343+0)/(343-23)*378 = 405.2 Hz.
Fp = Freq. heard by the person.
Vp = Velocity of the person.
Vs = Velocity of sound in air.
Vh = Velocity of the horn.
Fh = Freq. of the horn.
To find the frequency heard by a person standing in front of the car, you need to consider the Doppler effect. The Doppler effect describes the change in frequency or pitch of sound waves due to relative motion between the source of the sound and the observer.
In this case, the car is moving towards the person, so the frequency heard by the person will be higher than the frequency emitted by the car horn.
The formula for the Doppler effect can be written as:
f' = (v + vo) / (v + vs) * f
where:
f' is the frequency heard by the observer,
f is the frequency emitted by the source (car horn),
v is the speed of sound in air,
vo is the speed of the observer,
vs is the speed of the source.
In this scenario, the speed of sound in air is usually approximately 343 m/s.
Now, let's substitute the given values into the formula:
v = 343 m/s (speed of sound in air),
vo = 0 m/s (speed of the observer, assuming the person is stationary),
vs = 23 m/s (speed of the source, which is the car),
f = 378 Hz (frequency emitted by the car horn).
Plugging these values into the formula, we get:
f' = (343 + 0) / (343 + 23) * 378
f' = (343 / 366) * 378
f' ≈ 354 Hz
Therefore, a person standing in front of the moving car will hear a frequency of approximately 354 Hz.