Answer
$f_1=3430Hz$
$f_3=10300Hz$
$f_5=17200Hz$
Work Step by Step
Model the ear canal as a closed pipe of length 0.025m.
See figure 12-12. For a pipe that is closed at one end, the fundamental frequency is $f_1=\frac{v}{4 \mathcal{l}}$, and only the odd harmonic frequencies are present.
$f_1=\frac{343 m/s}{4 (0.025m)}=3430Hz$
$f_3=3f_1=10300Hz$
$f_5=5f_1=17200Hz$
In the figure, we see that the ear is most sensitive to frequencies between 3-4 kHz, which is approximately the fundamental resonant frequency of the ear canal.
There is again a region of enhanced sensitivity just above 10,000 Hz, corresponding to the first overtone of the ear canal.
