# US 10,313,820 B2 · Sub-band spatial audio enhancement

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- Number: US 10,313,820 B2
- Document ID: US10313820B2
- Status: Granted
- Kind: B2
- Application number: 15/646,821
- Filed: 2017-07-11
- Published: 2019-01-17
- Granted: 2019-06-04
- Earliest claimed: 2017-07-11
- Assignees: Boomcloud 360, Inc.
- Applicants: Boomcloud 360, Inc.
- Inventors: Zachary Seldess
- Web page: https://patentgrep.com/patent/US10313820B2

## CPC

- H04S 7/303: {Tracking of listener position or orientation}
- 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 3/008: {in which the audio signals are in digital form, i.e. employing more than two discrete digital channels (data reduction aspects thereof based on psychoacoustics G10L19/02)}
- H04R 3/14: Cross-over networks
- H04R 5/04: Circuit arrangements, {e.g. for selective connection of amplifier inputs/outputs to loudspeakers, for loudspeaker detection, or for adaptation of settings to personal preferences or hearing impairments (combinations of amplifiers H03F3/68; stereophonic systems H04S)}
- H04R 2499/11: Transducers incorporated or for use in hand-held devices, e.g. mobile phones, PDA's, camera's
- H04S 3/002: {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 2400/01: Multi-channel, i.e. more than two input channels, sound reproduction with two speakers wherein the multi-channel information is substantially preserved
- H04S 2400/13: Aspects of volume control, not necessarily automatic, in stereophonic sound systems
- H04S 2420/01: Enhancing the perception of the sound image or of the spatial distribution using head related transfer functions [HRTF's] or equivalents thereof, e.g. interaural time difference [ITD] or interaural level difference [ILD]
- H04S 2420/07: Synergistic effects of band splitting and sub-band processing
- H04S: STEREOPHONIC SYSTEMS
- 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)

## Abstract

An audio system provides for spatial enhancement of an audio signal including a left input channel and a right input channel. The system may include a spatial frequency band divider, a spatial frequency band processor, and a spatial frequency band combiner. The spatial frequency band divider processes the left input channel and the right input channel into a spatial component and a nonspatial component. The spatial frequency band processor applies subband gains to subbands of the spatial component to generate an enhanced spatial component, and applies subband gains to subbands of the nonspatial component to generate an enhanced nonspatial component. The spatial frequency band combiner combines the enhanced spatial component and the enhanced nonspatial component into a left output channel and a right output channel. In some embodiments, the spatial component and nonspatial component are separated into spatial subband components and nonspatial subband components for the processing.

## Claims

### Claim 1

A method for enhancing an audio signal having a left input channel and a right input channel, comprising:
processing the left input channel and the right input channel into a spatial component and a nonspatial component, the spatial component including a difference between the left input channel and the right input channel and the nonspatial component including a sum of the left input channel and the right input channel;
applying first subband gains to subbands of the spatial component to generate an enhanced spatial component, wherein applying the first subband gains to the subbands of the spatial component includes applying a first set of subband filters to the spatial component;
applying second subband gains to subbands of the nonspatial component to generate an enhanced nonspatial component, wherein applying the second subband gains to the subbands of the nonspatial component includes applying a second set of subband filters to the nonspatial component; and
combining the enhanced spatial component and the enhanced nonspatial component into a left output channel and a right output channel.

### Claim 2 (depends on 1)

The method of claim 1, wherein:
processing the left input channel and the right input channel into the spatial component and the nonspatial component includes processing the left input channel and the right input channel into spatial subband components and nonspatial subband components;
applying the first subband gains to the subbands of the spatial component to generate the enhanced spatial component includes applying the first subband gains to the spatial subband components to generate enhanced spatial subband components;
applying the second gains to the subbands of the nonspatial component to generate the enhanced spatial component includes applying the second subband gains to the nonspatial subband components to generate enhanced nonspatial subband components; and
combining the enhanced spatial component and the enhanced nonspatial component into the left output channel and the right output channel includes combining the enhanced spatial subband components and the enhanced nonspatial subband components.

### Claim 3 (depends on 2)

The method of claim 2, wherein processing the left input channel and the right input channel into spatial subband components and nonspatial subband components includes:
processing the left input channel and the right input channel into left subband components and right subband components; and
converting the left subband components and the right subband components into the spatial subband components and nonspatial subband components.

### Claim 4 (depends on 2)

The method of claim 2, wherein processing the left input channel and the right input channel into spatial subband components and nonspatial subband components includes:
converting the left input channel and the right input channel into the spatial component and the nonspatial component; and
processing the spatial component and the nonspatial component into the spatial subband components and the nonspatial subband components.

### Claim 5 (depends on 2)

The method of claim 2, wherein:
processing the left input channel and the right input channel into the spatial subband components and the nonspatial subband components includes:
converting the left input channel and the right input channel into the spatial component and the nonspatial component;
applying a forward fast Fourier transform (FFT) to the spatial component to generate the spatial subband components; and
applying the forward FFT to the nonspatial component to generate the nonspatial subband components; and
the method further includes, prior to combining the enhanced spatial component and the enhanced nonspatial component:
applying an inverse FFT to the enhanced spatial subband components to generate the enhanced spatial component; and
applying the inverse FFT to the enhanced nonspatial subband components to generate the enhanced nonspatial component.

### Claim 6 (depends on 2)

The method of claim 2, wherein the first subband gains are applied to the spatial subband components in parallel and the second subband gains are applied to the nonspatial subband components in parallel.

### Claim 7 (depends on 2)

The method of claim 2, wherein combining the enhanced spatial subband components and the enhanced nonspatial subband components includes:
processing the enhanced spatial subband components and the enhanced nonspatial subband components into enhanced left subband components and enhanced right subband components; and
combining the enhanced left subband components into the left output channel and the enhanced right subband components into the right output channel.

### Claim 8 (depends on 2)

The method of claim 2, wherein combining the enhanced spatial component and the enhanced nonspatial component into the left output channel and the right output channel includes:
combining the enhanced spatial subband components into the enhanced spatial component and the enhanced nonspatial subband components into the enhanced nonspatial component; and
converting the enhanced spatial component and the enhanced nonspatial component into the left output channel and the right output channel.

### Claim 9 (depends on 1)

The method of claim 1, further comprising:
applying time delays to the subbands of the spatial component to generate the enhanced spatial component; and
applying time delays to the subbands of the nonspatial component to generate an enhanced nonspatial component.

### Claim 10 (depends on 1)

The method of claim 1, wherein:
the first set of subband filters includes a first series of subband filters including a subband filter for each of the subbands of the spatial component; and
the second set of filters includes a second series of subband filters including a subband filter for each of the subbands of the nonspatial component.

### Claim 11 (depends on 1)

The method of claim 1, further comprising, prior to combining the enhanced spatial component and the enhanced nonspatial component, applying a first gain to the enhanced spatial component and a second gain to the enhanced nonspatial component.

### Claim 12 (depends on 1)

The method of claim 1, further comprising applying crosstalk cancellation to at least one of:
the left output channel and the right output channel; and
the left input channel and the right input channel.

### Claim 13 (depends on 1)

The method of claim 1, further comprising applying crosstalk simulation to at least one of:
the left output channel and the right output channel; and
the left input channel and the right input channel.

### Claim 14

A system for enhancing an audio signal having a left input channel and a right input channel, comprising:
a spatial frequency band divider configured to process the left input channel and the right input channel into a spatial component and a nonspatial component, the spatial component including a difference between the left input channel and the right input channel and the nonspatial component including a sum of the left input channel and the right input channel;
a spatial frequency band processor including:
a first set of subband filters configured to apply first subband gains to subbands of the spatial component to generate an enhanced spatial component; and
a second set of subband filters configured to apply second subband gains to subbands of the nonspatial component to generate an enhanced nonspatial component; and
a spatial frequency band combiner configured to combine the enhanced spatial component and the enhanced nonspatial component into a left output channel and a right output channel.

### Claim 15 (depends on 14)

The system of claim 14, wherein:
the spatial frequency band divider configured to process the left input channel and the right input channel into the spatial component and the nonspatial component includes the spatial frequency band divider being configured to process the left input channel and the right input channel into spatial subband components and nonspatial subband components;
the spatial frequency band processor configured to apply the first subband gains to the subbands of the spatial component to generate the enhanced spatial component includes the spatial frequency band processor being configured to apply the first subband gains to the spatial subband components to generate enhanced spatial subband components;
the spatial frequency band processor configured to apply the second subband gains to the subbands of the nonspatial component to generate the enhanced nonspatial component includes the spatial frequency band processor being configured to apply the second subband gains to the nonspatial subband components to generate enhanced nonspatial subband components; and
the spatial frequency band combiner configured to combine the enhanced spatial component and the enhanced nonspatial component into the left output channel and the right output channel includes the spatial frequency band combiner being configured to combine the enhanced spatial subband components and the enhanced nonspatial subband components.

### Claim 16 (depends on 15)

The system of claim 15, wherein the spatial frequency band divider includes:
a crossover network configured to process the left input channel and the right input channel into left subband components and right subband components; and
L/R to M/S converters configured to convert the left subband components and the right subband components into the spatial subband components and nonspatial subband components.

### Claim 17 (depends on 15)

The system of claim 15, wherein the spatial frequency band divider includes:
L/R to M/S converters configured to convert the left input channel and the right input channel into the spatial component and the nonspatial component; and
a crossover network configured to process the spatial component into the spatial subband components and the nonspatial component into the nonspatial subband components.

### Claim 18 (depends on 15)

The system of claim 15, wherein:
the spatial frequency band divider includes:
a L/R to M/S converter configured to convert the left input channel and the right input channel into the spatial component and the nonspatial component; and
a forward fast Fourier transform (FFT) configured to:
apply a forward FFT to the spatial component to generate the spatial subband components; and
apply the forward FFT to the spatial component to generate the spatial subband components; and
the spatial frequency band combiner includes:
an inverse FFT configured to, prior to the spatial frequency band combiner combining the enhanced spatial component and the enhanced nonspatial component:
apply an inverse FFT to the enhanced spatial subband components to generate the enhanced spatial component; and
apply the inverse FFT to the enhanced nonspatial subband components to generate the enhanced nonspatial component.

### Claim 19 (depends on 15)

The system of claim 15, wherein the spatial frequency band processor includes:
a first set of amplifiers configured to apply the first subband gains to the spatial subband components in parallel; and
a second set of amplifiers configured to apply the second subband gains to the nonspatial subband components in parallel.

### Claim 20 (depends on 15)

The system of claim 15, wherein the spatial frequency band combiner being configured to combine the enhanced spatial subband components and the enhanced nonspatial subband components includes the spatial frequency band combiner being configured to:
process the enhanced spatial subband components and the enhanced nonspatial subband components into enhanced left subband components and enhanced right subband components; and
combining the enhanced left subband components into the left output channel and the enhanced right subband components into the right output channel.

### Claim 21 (depends on 15)

The system of claim 15, wherein the spatial frequency band combiner being configured to combine the enhanced spatial subband components and the enhanced nonspatial subband components includes the spatial frequency band combiner being configured to:
combine the enhanced spatial subband components into the enhanced spatial component and the enhanced nonspatial subband components into the enhanced nonspatial component; and
convert the enhanced spatial subband component and the enhanced nonspatial component into the left output channel and the right output channel.

### Claim 22 (depends on 14)

The system of claim 14, wherein
the first set of subband filters are further configured to apply time delays to the subbands of the spatial component to generate the enhanced spatial component; and
the second set of subband filters are further configured to apply time delays to the subbands of the nonspatial component to generate the enhanced nonspatial component.

### Claim 23 (depends on 14)

The system of claim 14, wherein:
the first set of subband filters includes a first series of subband filters including a subband filter for each of the subbands of the spatial component; and
the second set of subband filters includes a second series of subband filters including a subband filter for each of the subbands of the nonspatial component.

### Claim 24 (depends on 14)

The system of claim 14, wherein the spatial frequency band combiner further includes:
a first amplifier configured to apply a first gain to the enhanced spatial component; and
a second amplifier configured to apply a second gain to the enhanced nonspatial component.

### Claim 25 (depends on 14)

The system of claim 14, further comprising a crosstalk cancellation processor configured to apply crosstalk cancellation to at least one of:
the left output channel and the right output channel; and
the left input channel and the right input channel.

### Claim 26 (depends on 14)

The system of claim 14, further comprising a crosstalk simulation processor configured to apply crosstalk simulation to at least one of:
the left output channel and the right output channel; and
the left input channel and the right input channel.

### Claim 27

A non-transitory computer readable medium configured to store program code, the program code comprising instructions that when executed by a processor cause the processor to:
process a left input channel and a right input channel of an audio signal into a spatial component and a nonspatial component, the spatial component including a difference between the left input channel and the right input channel and the nonspatial component including a sum of the left input channel and the right input channel;
apply first subband gains to subbands of the spatial component to generate an enhanced spatial component, wherein applying the first subband gains to the subbands of the spatial component includes applying a first set of subband filters to the spatial component;
apply second subband gains to subbands of the nonspatial component to generate an enhanced nonspatial component, wherein applying the second subband gains to the subbands of the nonspatial component includes applying a second set of subband filters to the nonspatial component; and
combine the enhanced spatial component and the enhanced nonspatial component into a left output channel and a right output channel.