US-12621630-B2 - System and method for audio diffusor

US12621630B2US 12621630 B2US12621630 B2US 12621630B2US-12621630-B2

Abstract

A system for processing audio data, comprising a diffusion data filter coupled to a source of digital audio data, the diffusion data filter configured to generate filtered audio data from the digital audio data. A delay coupled to the source of digital audio data, the delay configured to delay the digital audio data by a predetermined amount. A first multiplier configured to multiply the filtered audio data by a distance gain parameter to generate a first intermediate output. A second multiplier configured to multiply the delayed digital audio data by a complementary distance gain parameter to generate a second intermediate output. An adder configured to add the first intermediate output and the second intermediate output to generate an audio output.

Inventors

James David Johnston

Assignees

SPOTIFY AB

Dates

Publication Date: 20260505
Application Date: 20220725

Claims (16)

1 . A system for processing audio data, comprising: a diffusion data filter coupled to a source of digital audio data, the diffusion data filter configured to generate filtered audio data from the digital audio data, wherein the diffusion data filter simulates an arrival time being modified to be both before and after a center point of a time-varying data filter while maintaining a near-flat frequency response; a delay coupled to the source of the digital audio data, the delay configured to delay the digital audio data by a predetermined amount; a first multiplier configured to multiply the filtered audio data by a distance gain parameter to generate a first intermediate output; a second multiplier configured to multiply the delayed digital audio data by a complementary distance gain parameter to generate a second intermediate output; and a first adder configured to add the first intermediate output and the second intermediate output to generate an audio output.
2 . The system of claim 1 wherein the diffusion data filter comprises a sinusoidal variation component configured to generate the time-varying data filter from two or more filters.
3 . The system of claim 2 , wherein a first stereo audio channel is processed by the time-varying data filter and a second stereo audio channel is processed by a time reverse of the time-varying data filter.
4 . The system of claim 1 further comprising: a first filter; a first sinusoidal variation component configured to generate a first time-varying signal; and a third multiplier configured to receive the first filter and the first time-varying signal and to multiply the first filter and the first time-varying signal to generate a first filter output.
5 . The system of claim 4 further comprising: a second filter; a second sinusoidal variation component configured to generate a second time-varying signal; and a fourth multiplier configured to receive the second filter and the second time-varying signal and to multiply the second filter and the second time-varying signal to generate a second filter output.
6 . The system of claim 5 further comprising a second adder configured to receive the first filter output and the second filter output and to add the first filter output to the second filter output to generate the diffusion data filter.
7 . The system of claim 6 further comprising a time reversal system coupled to the diffusion data filter and configured to reverse a time value of the diffusion data filter to generate a reverse diffusion data filter.
8 . The system of claim 1 , wherein a first stereo audio channel is processed by the diffusion data filter and a second stereo audio channel is processed by a time reverse of the diffusion data filter.
9 . A method for processing audio data, comprising: generating filtered audio data from digital audio data by simulating an arrival time that is modified to be both before and after a center point of a time-varying data filter while maintaining a near-flat frequency response; delaying the digital audio data by a predetermined amount; multiplying the filtered audio data by a distance gain parameter to generate a first intermediate output; multiplying the delayed digital audio data by a complementary distance gain parameter to generate a second intermediate output; and adding the first intermediate output and the second intermediate output to generate an audio output.
10 . The method of claim 9 wherein generating the filtered audio data comprises a generating the time-varying data filter from two or more filters.
11 . The method of claim 10 , wherein a first stereo audio channel is processed by the time-varying data filter and a second stereo audio channel is processed by a time reverse of the time-varying data filter.
12 . The method of claim 9 wherein generating the filtered audio data comprises: generating a first time-varying signal; and multiplying a first filter and the first time-varying signal to generate a first filter output.
13 . The method of claim 12 wherein generating the filtered audio data comprises: generating a second time-varying signal; and multiplying a second filter and the second time-varying signal to generate a second filter output.
14 . The method of claim 13 further comprising adding the first filter output to the second filter output to generate a diffusion data filter.
15 . The method of claim 14 further comprising reversing a time value of the diffusion data filter to generate a reverse diffusion data filter.
16 . The method of claim 9 , further comprising processing a first stereo audio channel by a diffusion data filter and processing a second stereo audio channel by a time reverse of the diffusion data filter.

Description

TECHNICAL FIELD The present disclosure relates generally to audio data processing, and more specifically to a system and method for an audio diffusor that creates a spatial image external to the headphone listener. BACKGROUND OF THE INVENTION The ability to reproduce digitally-encoded audio data in a manner that sounds like a natural source external to the headphone listener is limited by the lack of acoustic artifacts particular to air propagation, especially in moving air. SUMMARY OF THE INVENTION A system for processing audio data is disclosed that includes a diffusion filter coupled to a source of digital audio data, where the diffusion filter generates filtered audio data from the digital audio data. A delay is coupled to the source of digital audio data and delays the digital audio data by a predetermined amount. A first multiplier multiplies the filtered audio data by a distance gain parameter to generate a first intermediate output and a second multiplier multiplies the delayed digital audio data by the compliment of the distance gain parameter to generate a second intermediate output. An adder combines the first intermediate output and the second intermediate output to generate an audio output. Other systems, methods, features, and advantages of the present disclosure will be or become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present disclosure, and be protected by the accompanying claims. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS Aspects of the disclosure can be better understood with reference to the following drawings. The components in the drawings may be to scale, but emphasis is placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views, and in which: FIG. 1 is a diagram of a system for generating a diffused audio signal from digitally encoded audio data, in accordance with an example embodiment of the present disclosure; FIG. 2 is a diagram of an algorithm for generating filter components for generating a diffused audio signal, in accordance with an example embodiment of the present disclosure; FIG. 3 is a diagram of a system for generating filter components for generating a diffused audio signal, in accordance with an example embodiment of the present disclosure; and FIG. 4 is a diagram of a system for processing digitally encoded two-channel audio data to generate a diffused audio signal, in accordance with an example embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION In the description that follows, like parts are marked throughout the specification and drawings with the same reference numerals. The drawing figures may be to scale and certain components can be shown in generalized or schematic form and identified by commercial designations in the interest of clarity and conciseness. FIG. 1 is a diagram of a system 100 for generating a diffused audio signal from digitally encoded audio data, in accordance with an example embodiment of the present disclosure. System 100 includes diffusion filter 102, delay 104, complementary distance gain 106, multiplier 108, multiplier 110 and adder 112, each of which can be implemented in hardware or a suitable combination of hardware and software, such as one or more algorithms operating on an audio data processor. Diffusion filter 102 can be implemented as one or more algorithms operating on an audio data processor that is configured to receive digitally-encoded audio data and to perform diffusion filtering of the digitally encoded audio data to generate filtered audio data. In one example embodiment, the filter applied by diffusion filter 102 can be configured to change dynamically, so as to create a time varying audio data signal that causes a listener to perceive the audio signal differently from a non-time-varying audio data signal. In this example, the perception of the listener can be that the audio data is from a natural source as opposed to a recording, such as a source that is located in a space outside of the apparent space that the listener experiences from recorded audio played over headphones. In particular, the creation of this filter specifically addresses the perception of air movement in a listening room, by moving parts of the signal both earlier and later than the mean path from the source to the listener, thereby simulating the sensation resulting from the actual acoustics in the room with moving air currents due to audience, heat, convection, HVAC, and the like. In this manner, signals can come both earlier than and later than the mean free path, which provides the desired effect. When a filter is created in this fashion, the amount of other signal modification i