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

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Homework Help Overview

The discussion revolves around the beat frequency heard when a saxophone and a trombone are both playing middle A (440 Hz) while the trombone is in a moving truck approaching the listener. Participants are exploring the implications of the Doppler effect on the perceived frequency of the trombone.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants are attempting to determine the correct frequencies involved in the beat frequency calculation and are questioning the role of the Doppler effect in this scenario. There is confusion regarding which frequency should be assigned to f1 and f2 in the beat frequency formula.

Discussion Status

Some participants have provided guidance on the relevance of the Doppler effect and the nature of beat frequencies, suggesting that the frequency from the trombone will be shifted due to the truck's motion. Multiple interpretations of the problem are being explored, particularly regarding the perceived frequency changes.

Contextual Notes

There is a noted absence of information regarding the velocity of the truck, which some participants believe may not be necessary for understanding the Doppler effect in this context.

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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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