Physically Informed Subtraction of a
String's Resonances from Monophonic,
Discretely Attacked Tones :
a Phase Vocoder Approach.
PhD thesis, National University of Ireland Maynooth.
A method for the subtraction of a string's oscillations from monophonic,
plucked- or hit-string tones is presented. The remainder of the subtraction
is the response of the instrument's body to the excitation, and potentially
other sources, such as faint vibrations of other strings, background
noises or recording artifacts. In some respects, this method is similar to a
stochastic-deterministic decomposition based on Sinusoidal Modeling Synthesis
[MQ86, IS87]. However, our method targets string partials expressly,
according to a physical model of the string's vibrations described in this thesis.
Also, the method sits on a Phase Vocoder scheme. This approach has
the essential advantage that the subtraction of the partials can take place
\instantly", on a frame-by-frame basis, avoiding the necessity of tracking the
partials and therefore availing of the possibility of a real-time implementation.
The subtraction takes place in the frequency domain, and a method
is presented whereby the computational cost of this process can be reduced
through the reduction of a partial's frequency-domain data to its main lobe.
In each frame of the Phase Vocoder, the string is encoded as a set of partials,
completely described by four constants of frequency, phase, magnitude
and exponential decay. These parameters are obtained with a novel method,
the Complex Exponential Phase Magnitude Evolution (CSPME), which is
a generalisation of the CSPE [SG06] to signals with exponential envelopes
and which surpasses the nite resolution of the Discrete Fourier Transform.
The encoding obtained is an intuitive representation of the string, suitable
to musical processing.
||String's Resonances from Monophonic; Discretely Attacked Tones; Phase Vocoder Approach;
||Science & Engineering > Computer Science
||26 Sep 2012 15:53
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