120
One set of relatively unexplored features, referred to as non-linear phenomena,
can also be observed as a component of whistles emissions. This phenomenon
includes subharmonics, frequencies jumps, biphonation and deterministic chaos.
These complex features are produced by nonlinearities in the vocal production system, where rather simple neural commands to the system can result in highly complex and individually variable acoustic signals (Fitch et al. 2002). The spectrogram
in Fig. 5.5 shows some non-linear acoustic phenomena.
5.3.2 Echolocation Clicks
As well as in whistles, we have been firstly categorizing echolocation into categories based on the visual inspection of spectrogram. The first category consists on
clicks that can be aurally assigned to one vocalizing animal and does not show any
other clicks belonging to a different train (Fig. 5.6A). The second category gathers
clicks produced by more than one animal, and therefore it is possible to visualize
many overlapped clicks (Fig. 5.6b). Again, depending on the main objective, both
Fig. 5.5 Examples of non-linear phenomena. Arrows point to: (a) Subharmonics, (b) Frequency
jump, (c) Deterministic chaos and (d) Biphonation
A. Andriolo et al.
One set of relatively unexplored features, referred to as non-linear phenomena,
can also be observed as a component of whistles emissions. This phenomenon
includes subharmonics, frequencies jumps, biphonation and deterministic chaos.
These complex features are produced by nonlinearities in the vocal production system, where rather simple neural commands to the system can result in highly complex and individually variable acoustic signals (Fitch et al. 2002). The spectrogram
in Fig. 5.5 shows some non-linear acoustic phenomena.
5.3.2 Echolocation Clicks
As well as in whistles, we have been firstly categorizing echolocation into categories based on the visual inspection of spectrogram. The first category consists on
clicks that can be aurally assigned to one vocalizing animal and does not show any
other clicks belonging to a different train (Fig. 5.6A). The second category gathers
clicks produced by more than one animal, and therefore it is possible to visualize
many overlapped clicks (Fig. 5.6b). Again, depending on the main objective, both
Fig. 5.5 Examples of non-linear phenomena. Arrows point to: (a) Subharmonics, (b) Frequency
jump, (c) Deterministic chaos and (d) Biphonation
A. Andriolo et al.