# US 2022/0103939 A1 · Apparatus for processing an audio signal

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- Number: US 2022/0103939 A1
- Document ID: US20220103939A1
- Status: Published application
- Kind: A1
- Application number: 17/434,173
- Filed: 2019-10-21
- Published: 2022-03-31
- Earliest claimed: 2019-10-21
- Assignees: Ask Industries GmbH
- Applicants: Ask Industries GmbH
- Inventors: Benjamin SELLAK
- Web page: https://patentgrep.com/patent/US20220103939A1

## CPC

- H04R 3/04: for correcting frequency response
- G10L 21/0388: Details of processing therefor
- H04R 3/12: for distributing signals to two or more loudspeakers {(specially adapted for hearing aids H04R25/407)}
- G10H 2210/311: Distortion, i.e. desired non-linear audio processing to change the tone colour, e.g. by adding harmonics or deliberately distorting the amplitude of an audio waveform
- G10H 2210/321: Missing fundamental, i.e. creating the psychoacoustic impression of a missing fundamental tone through synthesis of higher harmonics, e.g. to play bass notes pitched below the frequency range of reproducing speakers
- H04R 2430/03: Synergistic effects of band splitting and sub-band processing
- H04R 2430/20: Processing of the output signals of the acoustic transducers of an array for obtaining a desired directivity characteristic (H04R2203/12 takes precedence)
- H04R: LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS (producing sounds with frequency not determined by supply frequency G10K)
- G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
- G10H: ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE

## Abstract

Apparatus for processing an audio signal including an audio processing device configured to process, evaluate and modify an audio signal.

## Claims

### Claim 1

Apparatus for processing an audio signal comprising a number of samples, particularly so as to generate missing harmonics of low-frequency components in the audio signal, the apparatus comprising at least one audio processing device configured to:
process an audio signal in a time-dependent representation of the audio signal particularly in a half-wave representation of the audio signal;
determine an interval between a first zero-crossing and a further zero-crossing of the audio signal;
determine a first set of sample points in the interval, the first set of sample points comprising a number of sample points at first positions in the interval;
determine a second set of sample points in the interval, the second set of sample points comprising a number of sample points at second positions in the interval;
modify the audio signal in the interval, on basis of an audio signal modification rule, by changing positions of the sample points of the first set of sample points in the interval such that each sample point of the first set of sample points is changed from its respective first position in the first set of sample points to its respective second position in the second set of sample points;
apply the modified audio signal interval to the respective interval of the original audio signal so as to generate a modified audio signal; wherein
the audio processing device is configured to modify the audio signal on basis of an audio signal modification rule specifying a defined change of positions of the sample points of the first set of sample points in the interval such that each sample point of the first set of sample points is changed from its respective first position in the first set of sample points to its respective second position in the second set of sample points; wherein
the audio signal modification rule is or comprises a tilting function, configured to tilt a zero-crossing tangent of the audio signal in clockwise or counter-clockwise direction.

### Claim 2 (depends on 1)

Apparatus according to claim 1, wherein the audio signal modification rule specifies a defined change of positions of the sample points of the first set of sample points in the interval such that each sample point of the first set of sample points is changed from its respective first position in the first set of sample points to its respective second position in the second set of sample points such that the sample points of the second set of sample points are equally spaced.

### Claim 3 (depends on 2)

Apparatus according to claim 2, wherein the audio signal modification rule is or comprises a mapping function, particularly a monotonic mapping function, configured to map input sample points of the first set of sample having a respective first position to output sample points of the second set of sample points having a respective second position.

### Claim 4 (depends on 1)

Apparatus according to claim 1, wherein the audio signal processable or processed by the audio processing device has a specific original waveform, whereby
the audio processing device is configured to modify the specific original waveform of the audio signal to at least one target waveform of the audio signal.

### Claim 5 (depends on 4)

Apparatus according to claim 4, wherein the audio processing device is configured to modify the specific original waveform of the audio signal on basis of the or an audio signal modification rule specifying a defined change of the waveform of the audio signal from its original waveform to at least one target waveform of the audio signal.

### Claim 6 (depends on 4)

Apparatus according to claim 4, wherein the target waveform is a symmetric waveform, particularly a rectangular-waveform, a triangle-waveform or a needle-waveform, or an asymmetric waveform, particularly a sawtooth-waveform, preferably a straight or dented falling or rising sawtooth-waveform.

### Claim 7 (depends on 1)

Apparatus according to claim 1, wherein the audio processing device is configured to apply a skipping rule or skipping factor according to which at least one zero-crossing between a first zero-crossing and a further zero-crossing is not considered for determining the interval between the first zero-crossing and the further zero-crossing of the audio signal.

### Claim 8 (depends on 1)

Apparatus according to claim 1, further comprising at least one filter device, particularly a lowpass filter device, arranged to apply at least one filtering rule on the audio signal before the audio signal is processed by the audio processing device, and/or at least one filter device, particularly a lowpass filter device, arranged to apply at least one filtering rule on the audio signal after the audio signal was processed by the audio processing device.

### Claim 9 (depends on 1)

Apparatus according to claim 1, comprising a first audio processing device and at least one further audio processing device arranged in a parallel arrangement.

### Claim 10 (depends on 9)

Apparatus according to claim 9, wherein the first audio processing device is configured to modify the audio signal on basis of a first audio signal modification rule, by changing positions of the sample points of the first set of sample points in the interval such that each sample point of the first set of sample points is changed from its respective first position in the first set of sample points to its respective second position in the second set of sample points, and
the at least one further audio processing device is configured to modify the audio signal on basis of at least one further audio signal modification rule, by changing positions of the sample points of the first set of sample points in the interval such that each sample point of the first set of sample points is changed from its respective first position in the first set of sample points to its respective second position in the second set of sample point.

### Claim 11 (depends on 10)

Apparatus according to claim 10, wherein the first modification rule of the first audio processing device specifies a defined change of the waveform of the audio signal from its original waveform to at least one first target waveform of the audio signal, and the at least one further modification rule of the at least one further audio processing device specifies a defined change of the waveform of the audio signal from its original waveform to at least one further target waveform of the audio signal.

### Claim 12 (depends on 11)

Apparatus according to claim 11, wherein the first target waveform of the audio signal is opposite to the at least one further target waveform of the audio signal.

### Claim 13 (depends on 1)

Apparatus according to claim 1, wherein the first audio processing device is configured to apply a first skipping rule or skipping factor according to which at least one zero-crossing between a first zero-crossing and a further zero-crossing is not considered for determining the interval between the first zero-crossing and the further zero-crossing of the audio signal, and
the at least one further audio processing device is configured to apply at least one further skipping rule or skipping factor according to which at least one zero-crossing between a first zero-crossing and a further zero-crossing is not considered for determining the interval between the first zero-crossing and the further zero-crossing of the audio signal.

### Claim 14 (depends on 1)

Apparatus according to claim 1, wherein the at least one audio processing device is configured to determine the number of sample points between the first zero-crossing and the further zero-crossing such that is identical to the number of sample points in the respective interval in the original audio signal.

### Claim 15

(canceled)

### Claim 16

Method for processing an audio signal comprising a number of samples, particularly so as to generate missing low-frequency components in the audio signal, the method comprising:
processing an audio signal comprising a number of non-uniformly spaced sampling points in a time-dependent representation of the audio signal, particularly in a half-wave representation of the audio signal;
determining an interval between a first zero-crossing and a further zero-crossing of the audio signal;
determining a first set of sample points in the interval, the first set of sample points comprising a number of sample points at first positions in the interval;
determining a second set of sample points in the interval, the second set of sample points comprising a number of sample points at second positions in the interval;
modifying the audio signal in the interval, on basis of an audio signal modification rule, by changing positions of the sample points of the first set of sample points in the interval such that each sample point of the first set of sample points is changed from its respective first position in the first set of sample points to its respective second position in the second set of sample points;
applying the modified audio signal interval to the respective interval of the original audio signal so as to generate a modified audio signal; wherein
modifying the audio signal is carried out on basis of an audio signal modification rule specifying a defined change of positions of the sample points of the first set of sample points in the interval such that each sample point of the first set of sample points is changed from its respective first position in the first set of sample points to its respective second position in the second set of sample points; wherein
the audio signal modification rule is or comprises a tilting function, configured to tilt a zero-crossing tangent of the audio signal in clockwise or counter-clockwise direction.

### Claim 17

(canceled)