# US 7,412,220 B2 · Signal processing

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- Number: US 7,412,220 B2
- Document ID: US7412220B2
- Status: Granted
- Kind: B2
- Application number: 11/114,547
- Filed: 2005-04-26
- Published: 2005-11-03
- Granted: 2008-08-12
- Earliest claimed: 2004-04-26
- Inventors: Robert Patrick Beyer
- Web page: https://patentgrep.com/patent/US7412220B2

## CPC

- H04S 1/002: {Non-adaptive circuits, e.g. manually adjustable or static, for enhancing the sound image or the spatial distribution (control circuits for electronic adaptation of the sound field H04S7/30)}
- H04S: STEREOPHONIC SYSTEMS

## Abstract

Signal processing apparatus produces an audio signal suitable for conveying a psychoacoustic perception of a low frequency audio signal to a listener, the apparatus generates harmonics of the low frequency signal by shaping the waveform of the low frequency signal with respect to time and/or level. This may be achieved using a peak-hold generator and a rectifier, or using a peak-hold-decay generator.

## Claims

### Claim 1

Signal processing apparatus for producing an audio signal suitable for conveying a psychoacoustic perception of a low frequency audio signal to a listener, the apparatus including a peak-hold generator to generate harmonics of the low frequency signal by shaping the waveform of the low frequency signal with respect to time by tracking the low frequency signal to a substantially peak magnitude until a zero crossing, then tracking the signal again in the opposite polarity.

### Claim 2 (depends on 1)

Signal processing apparatus as claimed in claim 1 wherein the peak-hold generator includes a signal decay element to shape the output waveform of the low frequency signal with respect to level.

### Claim 3 (depends on 2)

Signal processing apparatus as claimed in claim 2 wherein the peak-hold generator generates odd and even harmonics.

### Claim 4

Signal processing apparatus for producing an audio signal suitable for conveying a psychoacoustic perception of a low frequency audio signal to a listener, the apparatus including a peak-hold generator means to generate harmonics of the low frequency signal by shaping the waveform of the low frequency signal with respect to time and a rectifier to generate even harmonics.

### Claim 5 (depends on 2)

Signal processing apparatus as claimed in claim 2 wherein the peak-hold generator comprises a peak-hold-decay generator.

### Claim 6 (depends on 2)

Signal processing apparatus as claimed in claim 2 wherein the low frequency waveform is shaped asymmetrically with respect to time and with respect to level.

### Claim 7

A method of processing a low frequency audio signal to produce an output audio signal suitable for conveying a psychoacoustic perception of a low frequency audio signal to a listener, the method including shaping the waveform of the low frequency signal with respect to time by tracking the low frequency signal to a substantially peak magnitude until a zero crossing then tracking the signal again in the opposite polarity.

### Claim 8 (depends on 7)

A method as claimed in claim 7 including the step of shaping the waveform of the low frequency signal with respect to time and with respect to level by tracking the low frequency signal to a substantially peak magnitude then allowing the peak to decay at a predetermined rate.