92
D. Rocchesso: Sound Processing
stochastic residual
sms
spectral modeling synthesis
guides
hysteresis
to give the stochastic residual. One popular implementation of the scheme in
figure 1 is found in the software sms, an acronym for spectral modeling synthe-
sis
Peak
Detection
and
Continuation
FFT
Additive
Synthesis
Spectral
Fitting
sound
Analysis
Window
phase
magnitude
Magnitude trajectory
Frequency trajectory
Phase trajectory
Deterministic
Component
Smoothing window
residual
Filter
Noise
Level
Coefficients
Figure 1: Separation of the sinusoidal components from a stochastic residual.
Peak detection and continuation
In order to separate the sinusoidal part from the residual we have to detect and
track the most prominent frequency peaks, as they are indicators of strong
sinusoidal components. One strategy is to draw "guides" across the STFT
frames [94], in such a way that prolongation by continuity fills local holes that
may occur in peak trajectories. If a guide detects missing evidence of the sup-
porting peak for more than a certain number of frames, the guide is killed.
Similarly, we start new guides as long as we detect a persistent peak. Therefore,
the generation and destruction of peaks is governed by hysteresis (see figure 2).
Birth
Death
Figure 2: Hysteretic procedure for guide activation and destruction.
In order to better capture the deterministic structure during transients, it is
1