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5 Acoustics in Biology and Medicine
Fig. 5.9 Oscillogram and spectrogram of a brown long-eared bat
Fig. 5.10 Oscillogram and spectrogram of the clicks from a bottle-nose dolphin
A large variety of fish can communicate with popping and grunting sounds, with
the purpose of keeping schools together, sending distress signals, or attracting the
opposite sex.
5.16 Physical Sound Wave Detection
Any phenomena in nature capable of generating sound has an inverse: The same
mechanisms can be used to detect sound. This reflexive property of such phenomena
has its basis in the time reversal symmetry of the laws of nature at the level
of atoms and molecules: Electrodynamics applied to atoms and electrons has the
property that for every dynamical solution, changing the time variable t to −t gives
another valid solution. At a macroscopic level, the principle still holds, except it
may happen that the time-reversed solution is highly improbable. Evidence for this
possibility comes from the production of entropy in the forward process. If the
forward process has little or no entropy production, then the process which has all
the dynamical components with an odd power of time reversed (such as speed) is
also a macroscopic possibility.
5 Acoustics in Biology and Medicine
Fig. 5.9 Oscillogram and spectrogram of a brown long-eared bat
Fig. 5.10 Oscillogram and spectrogram of the clicks from a bottle-nose dolphin
A large variety of fish can communicate with popping and grunting sounds, with
the purpose of keeping schools together, sending distress signals, or attracting the
opposite sex.
5.16 Physical Sound Wave Detection
Any phenomena in nature capable of generating sound has an inverse: The same
mechanisms can be used to detect sound. This reflexive property of such phenomena
has its basis in the time reversal symmetry of the laws of nature at the level
of atoms and molecules: Electrodynamics applied to atoms and electrons has the
property that for every dynamical solution, changing the time variable t to −t gives
another valid solution. At a macroscopic level, the principle still holds, except it
may happen that the time-reversed solution is highly improbable. Evidence for this
possibility comes from the production of entropy in the forward process. If the
forward process has little or no entropy production, then the process which has all
the dynamical components with an odd power of time reversed (such as speed) is
also a macroscopic possibility.