Non-linear tone generator
AssigneeChromatic Research, Inc.
InventorAvery L. Wang
Life of this patent
Estimating the term…
Abstract
A method and apparatus for producing a tone (e.g. for music) without use of a waveform memory and using a feedback loop. The feedback loop includes a waveform generator which calculates, in real time, a parabolic approximation to a sine wave. The feedback loop includes a delay phase differencer to eliminate hunting. The output waveform from the feedback loop is provided to a sine function generator which approximates a sine value using a third order polynomial, to provide the output tone.
Claims25
A method for producing a tone, comprising the steps of:
- generating a signal by a calculation;
- multiplying the generated signal by a feedback parameter to produce a product signal;
- providing a base frequency;
- and
- feeding back a sum of the base frequency and the product signal as an input value to the step of generating.
An apparatus for producing a tone, comprising:
- a waveform generator producing a signal by a calculation;
- a multiplier receiving the signal from the waveform generator and a feedback parameter and producing a product signal therefrom;
- an adder connected to the multiplier and to a source of a base frequency for adding the product signal and the base frequency;
- and
- a feedback loop coupling a sum output by the adder to an input of the waveform generator.
A method for producing a tone by synthesizing a waveform using a polynomial of a variable x, comprising the steps of:
- providing a set of at least three coefficients .alpha..sub.0, .alpha..sub.1, .alpha..sub.2,;
- calculating an approximation of a sine value of the variable x using a polynomial of the variable x by the steps of:
- providing a value of the variable x;
- computing by a first operation a value y that is a sum of x.sup.2 and a constant;
- performing no more than three more operations a, b, c to compute respectively:
- (a) .alpha..sub.0 y+.alpha.1;
- (b) y(.alpha..sub.0 y+.alpha..sub.1)+.alpha..sub.2 ;
- and
- (c) y(y(.alpha..sub.0 y+.alpha..sub.1)+.alpha..sub.2);
- and
- generating a tone from the result of operation (c) using the calculated approximation of the sine value of the variable x using a multiply operation no more than four times.
Dependencies are inferred from the claim text.