A half-open pipe is constructed to produce a fundamental frequency of 230 Hz when the air temperature is 17 °C. It is used in an overheated building when the temperature is 39 °C. Neglecting thermal expansion in the pipe, what frequency will be heard?

1 answer

The first temperature is T1 =273 +17 = 290K
The speed of sound at T1 is v1=332•sqrt(T1/273) =
=332•sqrt(290/273) =342.18 m/s.
v= L•f.
The length of pipe is L=v1/f1=342.18 /230=1.49 m
The second temperature is T2 =273 +39 = 312K
The speed of sound at T2 is v2=332•sqrt(T2/273) =
=332•sqrt(312/273) =354.9 m/s.
f2=v2/L=354.9/1.49=238.20 Hz