Musical synthesizer combining deterministic and stochastic waveforms

• US 5,029,509 A
• Filed: 11/03/1989
• Issued: 07/09/1991
• Est. Priority Date: 05/10/1989
• Status: Expired due to Term

• Current Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford Management Co.)
• Original Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford Management Co.)
• Inventors: Serra, Xavier, Smith, Julius
• Primary Examiner(s): Witkowski, Stanley J.
• Application Number:
  US07/431,594
• Time in Patent Office: 613 Days
• Field of Search: 84/622, 84/623, 84/625, 84/627, 84/DIG. 9, 84/659-661, 84/663
• US Class Current: 84/625
• CPC Class Codes: G10H 1/125 using a digital filter
• CPC Class Codes: G10H 2250/031 Spectrum envelope processing
• CPC Class Codes: G10H 2250/065 Lattice filter, Zobel network, constant resistance filter or X-section filter, i.e. balanced symmetric all-pass bridge network filter exhibiting constant impedance over frequency
• CPC Class Codes: G10H 2250/211 Random number generators, pseudorandom generators, classes of functions therefor musical processes using white noise or nonwhite noise generators G10H2250/295; noise formant generator G10H2250/495; magnetic or electromagnetic noise shielding G10H2220/565
• CPC Class Codes: G10H 2250/235 Fourier transform; Discrete Fourier Transform [DFT]; Fast Fourier Transform [FFT]
• CPC Class Codes: G10H 2250/291 Kaiser windows; Kaiser-Bessel Derived [KBD] windows, e.g. for MDCT
• CPC Class Codes: G10H 7/105 using Fourier coefficients
• CPC Class Codes: Y10S 84/09 Filtering

Abstract

A musical sound analyzer and synthesizer uses a model that considers a sound to be composed of two types of elements: a deterministic component plus a stochastic component. The deterministic component is represented as a series of sinusoids, with an amplitude and a frequency function for each sinusoid. The stochastic component is represented as a series of magnitude spectral envelopes. From this representation, sounds can be synthesized that, in the absence of modifications, can behave as perceptual identities, that is, they are perceptually equal to the original sound. In addition, stored representations of sounds can be easily modified in a musical synthesizer to create a wide variety of new sounds.

Claims

1. A sound waveform synthesizer, comprising:

storage means for storing data denoting a sequence of sound partials and data denoting a corresponding sequence of spectral envelopes;

sinusoidal waveform generator means coupled to said storage means for generating a sequence of first waveforms during a sequence of time frames, including means for generating sinusoidal waveforms during each said time frame corresponding to a selected one of said sound partials denoted by data stored in said storage means;

stochastic waveform generator means coupled to said storage means for generating a sequence of stochastic waveforms during said sequence of time frames, including means for generating stochastic waveforms during each said time frame having a spectral envelope corresponding to a selected one of said spectral envelopes denoted by data stored in said storage means; and

means for generating a synthesized sound waveform, including means for combining said first waveforms and said stochastic waveforms;

said stochastic waveform generator means including

noise generating means for generating a noise signal; and

filter means coupled to said storage means and said noise generating means for generating a stochastic waveform, including means for filtering said noise signal with a time varying frequency response during said sequence of time frames, said frequency response during each said time frame corresponding to a selected one of said spectral envelopes denoted by data stored in said storage means.

2. A sound waveform synthesizer as set forth in claim 1, wherein said data denoting a sequence of spectral envelopes includes data denoting a set of lattice filter coefficients for each of a sequence of time frames;

said filter means in said stochastic waveform generator means comprising

lattice filter means for filtering said noise signal with a time varying frequency response during said sequence of time frames, said frequency response during each said time frame corresponding to a selected one of said sets of lattice filter coefficients denoted by data storage in said storage means.

3. A sound waveform synthesizer as set forth in claim 1,

said noise generating means comprising random number generating means for generating a set of random phase values for each said time frame;

said filter means including;

stochastic spectra means for generating a set of complex spectral values for each said time frame, including means for combining said set of random phase values for each said time frame with a selected one of said spectral envelopes denoted by data stored in said storage means; and

inverse Fourier transform means coupled to said stochastic spectra means for generating a stochastic waveform for each said time frame by inverse fourier transforming said complex spectral values.

4. A sound waveform synthesizer as set forth in claim 1, further including

transform means coupling said storage means with said sinusoidal waveform generator means, including means for transforming selected ones of said sound partials stored in said trajectory storage means, thereby altering the acoustic qualities of said sequence of first waveforms.

5. A sound waveform synthesizer as set forth in claim 1, further including

envelope transform means coupling said storage means with said stochastic waveform generator means, including means for transforming selected ones of said spectral envelopes stored in said storage means, thereby altering the acoustic qualities of said sequence of stochastic waveforms.

6. A sound waveform synthesizer, comprising:

trajectory storage means for storing sound partials, including means for storing corresponding sets of magnitude and frequency trajectories, each set representing a sound partial;

envelope storage means for storing spectral envelopes, each spectral envelope corresponding to the stochastic portion of a predefined sound;

sinusoidal waveform generator means coupled to said trajectory storage means for generating a first waveform corresponding to selected sound partials stored in said trajectory storage means;

noise generating means for generating a noise signal;

filter means coupled to said envelope storage means and said noise generating means for generating a stochastic waveform, including means for filtering said noise signal with a frequency response equal to a selected spectral envelope stored in said envelope storage means; and

means for generating a synthesized sound waveform, including means for combining said first waveform and said stochastic waveform.

7. A sound waveform synthesizer as set forth in claim 6, further including

transform means coupling said trajectory storage means with said sinusoidal waveform generator means, including means for transforming selected ones of said sound partials stored in said trajectory storage means, thereby altering the acoustic qualities of said first waveform.

8. A sound waveform synthesizer as set forth in claim 6, further including

envelope transform means coupling said envelope storage means with said filter means, including means for transforming selected ones of said spectral envelopes stored in said envelope storage means, thereby altering the acoustic qualities of said stochastic waveform.

9. A method of generating sound waveforms, the steps of the method comprising:

storing data denoting a sequence of sound partials and data denoting a corresponding sequence of spectral envelopes;

generating a sequence of first waveforms during a sequence of time frames, including generating a plurality of sinusoidal waveforms during each said time frame corresponding to a selected one of said stored sound partials; and

generating a sequence of stochastic waveforms during said sequence of time frames, including generating stochastic waveforms during each said time frame having a spectral envelope corresponding to a selected one of said stored spectral envelopes; and

combining said first waveforms and said stochastic waveforms to generate a synthesized sound waveform;

said second generating step including the steps of

generating a noise signal; and

filtering said noise signal with a time varying frequency response during said sequence of time frames, said frequency response during each said time frame corresponding to a selected one of said stored spectral envelopes.

10. A method of generating sound waveforms, as set forth in claim 9, wherein said stored data denoting a sequence of spectral envelopes includes data denoting a set of lattice filter coefficients for each of a sequence of time frames;

said noise filtering step including the step of filtering said noise signal with a lattice filter employing time varying lattice filter coefficients corresponding to a sequence of said sets of lattice filter coefficients.

11. A method of generating sound waveforms, as set forth in claim 9, said second generating step including the steps of:

said noise generating step including generating a set of random phase values for each said time frame;

said noise filtering step including the steps of;

generating a set of complex spectral values by combining said set of random phase values for each said time frame with a selected one of said spectral envelopes denoted by said stored data; and

inverse fourier transforming said complex spectral values for each said time frame.

12. A method of generating sound waveforms, as set forth in claim 9, said first generating step including the step of transforming selected ones of said stored sound partials and thereby altering the acoustic qualities of said sequence of first waveforms.

13. A method of generating sound waveforms, as set forth in claim 9, said second generating step including the step of transforming selected ones of said stored spectral envelopes and thereby altering the acoustic qualities of said sequence of stochastic waveforms.

14. A sound waveform synthesizer, comprising:

storage means for storing data denoting a sequence of sound partials and data denoting a corresponding sequence of spectral envelopes;

sinusoidal component generator means coupled to said storage means for generating a sequence of sinusoidal waveform components during a sequence of time frames, including means for generating sinusoidal waveform components during each of said time frame corresponding to a selected one of said sound partials denoted by data stored in said storage means;

stochastic component generator means coupled to said storage means for generating a sequence of stochastic waveform components during said sequence of time frames, including means for generating stochastic waveform components during each said time frame having a spectral envelope corresponding to a selected one of said spectral envelopes denoted by data stored in said storage means; and

means for generating a synthesized sound waveform, including means for combining said sinusoidal waverform and stochastic waveform components;

said stochastic component generator means including;

noise generating means for generating a noise signal; and

noise shaping means coupled to said storage means and said noise generating means for combining said noise signal with selected ones of said spectral envelopes denoted by data stored in said storage means so as to generate spectrally shaped stochastic waveform components.

15. A sound waveform synthesizer as set forth in claim 14, wherein said noise shaping means comprises inverse fourier transforming means for generating a stochastic waveform for each said time frame by inverse fourier transforming said noise signal combined with selected ones of said spectral envelopes.

16. A sound waveform synthesizer as set forth in claim 14, further including

transform means coupling said storage means with said sinusoidal waveform generator means, including means for transforming selected ones of said sound partials stored in said trajectory storage means, thereby altering the acoustic qualities of said sequence of first waveforms.

17. A sound waveform synthesizer as set forth in claim 14, further including

envelope transform means coupling said storage means with said stochastic waveform generator means, including means for transforming selected ones of said spectral envelopes stored in said storage means, thereby altering the acoustic qualities of said sequence of stochastic waveforms.