Feature enhancement: pulsing

A sharp contrast is seen between the `crowded' energy map of the modulated oscillations (individual minima and maxima of the signal identified by the Mexican hat wavelet) in section 13 and and the `smooth' presentation of the norm-Morlet transforms of the same data in section 15. It may be of interest to keep the emphasis on individual events forming a sustained `wavetrain', but without assuming that the wavetrain is periodic. This can be achieved by the following simple algorithm:

1. construct an energy map based on individual events.
2. smooth the map by merging the events that are `close enough' to each other. This is achieved by scale-dependent filtering, in which the filter size is proportional to the wavelet size.

Smoothed energy map of can be compared to the Morlet-transform.

Differences with Figs 17-19 are seen in the vertical spread of the contours, with better spectral localization using the locally-periodic Morlet wavelet, and in the horizontal spread -- particularly for the modulated wave -- where single events can contribute.