When applying our model on a continuous
sound wave (as opposed to a single pulse situation),
one should take into account the resonance
phenomenon. This means that for input sounds
of half-wavelength, which is about the size of a
stethoscope, we might get a resonance that will
cause the sound amplification to be of a much
higher magnitude than the one predicted by
equation (12). Let us demonstrate this point by
considering one possible resonance mode, generated
by a standing sound wave formed along the
main symmetry axes of a stethoscope funnel. In
this case one may consider the stethoscope as an
open-ended tube of length h. Therefore, the resonant
frequencies are given by [5, 11]: