where T is the air temperature measured in
Celsius scale. It is important to note that the resonant
frequencies fn which are defined in (13a) and
(13b) are not the only possible resonant modes.
For instance, additional resonant frequencies
are defined by the geometry of a funnel. One of
the ways to reduce the number of possible resonant
modes is to smoothly round the form of the
stethoscope’s walls (see figure 2). Discussing all
the possible resonance frequencies is beyond the
scope of the present work.