Lab 8: Sinusoidal plus Residual Modeling
The Sinusoidal plus Residual Modeling assumes that the sinusoids
model the stable partials or harmonics of a sound, which
could also be called the deterministic component of the sound. The
residual models the noisy part of the sound, which could also be called
the stochastic component of the sound. The residual is obtained by
subtraction the sinusoidal components from the original sound, which
then can be modeled as an stochastic signal.
In this lab we will
be subtracting the sinusoidal components in the frequency domain. In
order to do that we will have to analyze the sound with a
Blackman-Harris 92dB window in order to be able to subtract the main
lobe of that window in the spectrum.
To do this lab you can start from the harmonicmodel.m using the functions given in lab-7, converting it to sinesplusresmodel.m
8.1 Sinusoidal subtraction1. Subtract the complex spectrum of the sines obtained by the function genspecsines (ex: Xsines = genspecsines(ihloc,ihmag,ihphase,M,N,bh92lobe);) from the original complex spectrum at each frame, (ex: Xres = X - Xsines;).
Synthesize the residual sound by performing the inverse-fft of the
residual spectrum and applying the same synthesis window used in the
harmonic model. ex:
- fftbuffer = real(ifft(Xres)); % inverse FFT
- x1((M+1)/2:M) = fftbuffer(1:(M+1)/2);
- x1(1:(M-1)/2) = fftbuffer(N-(M-1)/2+1:N);
- res(pin+1:pin+M) = res(pin+1:pin+M) + x1(1:M) .* ws;
8.2 Residual approximation1. Approximante the magnitude of the residual spectrum by line segments given a step size that will be the number of bins to approximate by a single value. ex:
the residual approximation by generating noise with the frequency
characteristics of the spectral envelope of the residual.
- mXres = abs(Xres(1:N2));
- resenv = zeros(floor(N2/step), 1);
- for i = 1:step:(N2-step);
- Generate a new residual magnitude spectrum, mXres, by interpolating the approximation, resenv, to the N2 size.
- Generate the phase spectrum, pXres, by filling it with random numbers from 0 to 2pi.
- Create the complex spectrum by Xres = mXres.*cos(pXres)+i*mXres.*sin(pXres);
8.3 Tunning the model parametersAnalyze several harmonic sounds with the obtained model. The function should be defined by
[y, sines, res] = sinesplusresmodel(x, fs, w, N, H, mthreshold, nHarms,
minf0, maxf0, maxf0error, maxharmdev, resapproxstep)
- % x: input array sound
- % fs: sampling rate
- % w: window (odd size), ex: blackmanharris(1023)
- % N: FFT size, ex: 1024
- % H: hop size, ex: 512
- % mthreshold: threshold in dB used for peak detection, ex: -20
- % nHarms: maximum number of harmonics to find, ex: 40
- % minf0: minimum frequency for f0, ex: 80
- % maxf0: maximim frequency for f0, ex: 500
- % maxf0error: maximum error allowed in the f0 detection, ex: 5
- % maxharmdev: maximum deviation allowed in detecting harmonics, as a product, ex: .2
- % resapproxstep: step increment in bins in spectral noise approximation, ex: 10
different parameters, specially window-size, FFT
size, hop-size, magnitude threshold, number of harmonics, maximum
f0 error, and maximum harmonic deviation.
- Describe the effect of these changes
8.4 Trying another model implementationYou can try a complete implementation of the model by using the sms.m code, which does not perform the residual approximation. Compare the two implementations.