Beat freuqency of a saxophone and trombone at middle A (440 Hz)

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When a saxophone and trombone both play middle A at 440 Hz, the beat frequency heard is 4 Hz. The discussion revolves around determining the frequency of the trombone, with calculations suggesting two possibilities: 444 Hz and 436 Hz. Since the trombone is approaching, the frequency heard will be higher than 440 Hz due to the Doppler effect. Therefore, the correct frequency for the trombone is 444 Hz. Understanding the Doppler shift is crucial in this context, as it affects the perceived pitch when the source is moving towards the listener.
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If you are playing your saxophone at middle A (440 Hz) and a trombone also playing middle A (440 Hz) in the open bed of a pickup truck is approaching you. The beat frequency you hear is 4 Hz. What frequency do you hear from the trombone?

The formula I know I am supposed to use is:
fbeat=f1-f2

but for my question what is f1 and f2. two answers i get depending on me putting 440 for f1 and f2 and the fbeat of 4 is 440 and 436.
Which one is right?
 
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Have you had anything on the Doppler effect yet? The truck with the trombone player is approaching you. Is 440 and 436 the only solution?

BTW, it doesn't actually matter for the calculation which frequency is f1. The beat frequency is generally stated as

b.f. = | f1 - f2 | ...
 


dynamicsolo said:
Have you had anything on the Doppler effect yet? The truck with the trombone player is approaching you. Is 440 and 436 the only solution?

BTW, it doesn't actually matter for the calculation which frequency is f1. The beat frequency is generally stated as

b.f. = | f1 - f2 | ...

Sorry I meant 444 and 436. They are the only answer choices given, but I can't figure out which one is the correct answer.
I thought of doppler effect but the velocity of the truck is not given.
 


You don't need the truck's velocity for this problem, but only the concept of Doppler shift. You are going to hear your own note at A-440, so that is one of the frequencies (doesn't matter which). If the truck is coming AT YOU, will the tone you hear from it be shifted higher or lower from 440 Hz?
 


dynamicsolo said:
You don't need the truck's velocity for this problem, but only the concept of Doppler shift. You are going to hear your own note at A-440, so that is one of the frequencies (doesn't matter which). If the truck is coming AT YOU, will the tone you hear from it be shifted higher or lower from 440 Hz?

Oh...it should be higher then, since it's coming closer.
 


And there you go!
 


thanks
 

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