# Doppler effect: sound out of tune

1. Apr 12, 2008

### dragonlau

1. The problem statement, all variables and given/known data
Two trumpet players tune their instruments to exactly 440 Hz. Find the difference in the apparent frequencies due to the Doppler effect if one plays her instrument while marching away from an observer and the other plays while marching toward the observer. Is this enough to make them sound out of tune? (Assume 1 m/s as a reasonable marching speed).

2. Relevant equations
$$f=f\frac{V}{V-V_s}$$
and
$$f=f\frac{V}{V+V_s}$$

3. The attempt at a solution
$$f=440\frac{343}{343-1}=441 Hz$$
and
$$f=440\frac{343}{343+1}=439 Hz$$
However, how should I know whether this is enough to make them sound out of tune? And am I correct with the difference in the apparent frequencies due to the Doppler effect?

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