Audio filter bank with decorrelation components

Abstract

A multi-input, multi-output audio processing is implemented as a linear system for use in an audio filter bank to convert a set of frequency-domain input audio signals into a set of frequency-domain output audio signals. The transfer function from one input to one output is defined as a frequency-dependent gain function. In some implementations, the transfer function includes a direct component that is substantially defined as a frequency-dependent gain and one or more decorrelating components having a frequency-varying group phase response. The transfer function is formed by a set of sub-band functions, where each sub-band function is formed by a set of corresponding component transfer functions that include the direct component and one or more decorrelating components.

Description

[0001] Cross - reference to related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 62 / 895,096, filed on September 3, 2019, which is hereby incorporated by reference in its entirety. Technical field

[0003] The present disclosure generally relates to audio signal processing, and more particularly to audio signal processing for processing a set of one or more frequency - domain input audio signals to create a set of new one or more frequency - domain output audio signals. Background art

[0004] In audio signal processing, a set of input audio signals is typically converted into a new set of audio output signals, where the number of output audio signals can be the same as or greater than the number of input audio signals. For example, a surround sound system can convert two input audio signals (e.g., stereo audio signals) into five output audio signals by using linear matrix operations. The linear matrix operations apply a matrix to the input audio signals, and the matrix contains coefficients that can vary according to time or frequency. When the input audio signals have been subjected to known processing, the linear matrix operations can also determine the covariance of the output audio signals. Summary of the invention

[0005] A multi - input, multi - output audio processing is implemented as a linear system for an audio filter bank to convert a set of frequency - domain input audio signals into a set of frequency - domain output audio signals. The transfer function from one input to one output is defined as a frequency - dependent gain function. In some implementations, the transfer function includes a direct component that is substantially defined as a frequency - dependent gain and one or more decorrelation components having a frequency - varying group phase response. The transfer function is formed by a set of sub - band functions, where each sub - band function is formed by a set of corresponding component transfer functions that include the direct component and one or more decorrelation components.

[0006] In some implementations, a method of converting a set of frequency-domain input audio signals to a set of frequency-domain output audio signals includes: using one or more processors to compute each frequency-domain output audio signal as a sum of filtered frequency-domain input audio signals, where each filter for filtering the frequency-domain input audio signals is characterized by a complex gain function over a corresponding sub-band frequency range of the frequency-domain input audio signals, where the contribution of the frequency-domain input audio signals to the frequency-domain output audio signals is determined by a composite frequency-domain gain vector, and the composite frequency-domain gain vector is obtained by: using the one or more processors to compute a set of component frequency-domain gain vectors, where at least one of the component frequency-domain gain vectors is a decorrelated component frequency-domain gain vector formed by enhancing the component frequency-domain gain vector with an additional component frequency-domain gain vector having a modified frequency response to create a decorrelation effect; and using the one or more processors to sum the component frequency-domain gain vectors to form the composite frequency-domain gain vector.

[0007] In some implementations, the decorrelated component frequency-domain gain vector is formed by scaling the at least one of the component frequency-domain vectors by a component gain value.

[0008] In some implementations, one or more of the component frequency-domain gain vectors include a phase response that varies over a sub-band frequency range, thereby providing a group delay that is substantially constant over the sub-band frequencies, and where the group delay is substantially constant if the fluctuations in the group delay are small enough to be perceptually insignificant to a listener.

[0009] In some implementations, one or more of the component frequency-domain gain vectors include a phase response that varies over the sub-band frequency range, thereby providing a group delay that varies over the sub-band frequency range to provide a decorrelation effect.

[0010] In some implementations, the decorrelated component frequency-domain gain vector is formed by multiplying the component frequency-domain gain vector by a decorrelation function.

[0011] In some implementations, an audio filter bank having decorrelated components includes: a converter configured to convert a set of time-domain input audio signals to a set of frequency-domain input audio signals; and a linear mixer configured to convert the set of frequency-domain input audio signals to a set of frequency-domain output audio signals, where each frequency-domain output audio signal is a sum of filtered frequency-domain input audio signals, where each filter for filtering the frequency-domain input audio signals is characterized by a complex gain function over a corresponding sub-band frequency range of the frequency-domain input audio signals, and the contribution of the frequency-domain input audio signals to the frequency-domain output audio signals is determined by a composite frequency-domain gain vector.

[0012] In some implementations, the composite frequency-domain gain vector is obtained by: calculating a set of component frequency-domain gain vectors, where at least one of the component frequency-domain gain vectors is a decorrelated component frequency-domain gain vector formed by enhancing the component frequency-domain gain vector with an additional component frequency-domain gain vector having a modified frequency response to create a decorrelation effect on the frequency-domain output audio signal; and summing the component frequency-domain gain vectors to form the composite frequency-domain gain vector.

[0013] In some implementations, the decorrelated component frequency-domain gain vector is formed by scaling the at least one of the component frequency-domain vectors by a component gain value.

[0014] In some implementations, one or more of the component frequency-domain gain vectors include a phase response that varies within a subband frequency range, thereby providing a group delay that is substantially constant over the subband frequencies, and where the group delay is substantially constant if the fluctuations in the group delay are small enough to be perceptually insignificant to a listener.

[0015] In some implementations, one or more of the component frequency-domain gain vectors include a phase response that varies within the subband frequency range, thereby providing a group delay that varies within the subband frequency range to provide a decorrelation effect on the frequency-domain output audio signal.

[0016] In some implementations, the decorrelated component frequency-domain gain vector is formed by multiplying the component frequency-domain gain vector by a decorrelation function.

[0017] In some implementations, a filter bank-based audio system includes: a converter configured to convert a set of time-domain input audio signals into a set of frequency-domain input audio signals; and a linear mixer configured to convert the set of frequency-domain input signals into a set of frequency-domain output signals, where the linear mixer includes weighting coefficients that provide a frequency-dependent gain function, the frequency-dependent gain function including a direct component defined as a frequency-dependent gain and one or more decorrelated components having a frequency-varying group phase response, and where the frequency-dependent gain is formed by a set of subband functions, where each subband function is formed by a set of corresponding component transfer functions including a direct component and one or more decorrelated components.

[0018] Other implementations disclosed herein relate to systems, devices, and computer-readable media. Details of the disclosed implementations are set forth in the following figures and description. Other features, objectives, and advantages will become apparent from the description, figures, and claims.

[0019] Certain embodiments disclosed herein provide one or more of the following advantages. The disclosed implementation integrates decorrelation processing into an audio filter bank, thus allowing an input audio signal to be mapped to an output audio signal using a single linear mixer, resulting in a lower latency compared to conventional audio filter banks that perform decorrelation processing using multiple linear mixers. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In the drawings, for ease of description, a specific configuration or order of schematic elements such as those representing devices, units, instruction blocks, and data elements is shown. However, those skilled in the art should understand that the specific order or configuration of the schematic elements in the drawings is not intended to imply a need for a specific processing order or sequence, or separate processing. Additionally, the inclusion of schematic components in the figures is not intended to imply that such an element is required in all embodiments, or that the features represented by such an element in some implementations may not be included in or combined with other elements.

[0021] Furthermore, in the drawings, where connection elements such as solid lines, dashed lines, or arrows are used to depict a connection, relationship, or association between or among two or more other schematic elements, the absence of any such connection element is not intended to imply that no connection, relationship, or association may exist. In other words, some connections, relationships, or associations between elements are not shown in the drawings so as not to obscure the invention. Additionally, for ease of illustration, a single connection element is used to represent multiple connections, relationships, or associations between elements. For example, where the connection element represents the communication of signals, data, or instructions, those skilled in the art should understand that this element represents one or more signal paths that may be required to effect the communication.

[0022] Figure 1 Shown is filtering a set of input audio signals using a filter array to produce a set of audio output signals, according to one or more embodiments.

[0023] Figure 2 Shown is a desired frequency response curve, according to one or more embodiments.

[0024] Figure 3 Shown is a set of filter bank frequency responses, according to one or more embodiments.

[0025] Figure 4 Shown is the bandpass response of a typical component frequency-domain gain vector, according to one or more embodiments.

[0026] Figure 5 Shown is the frequency response of a subband filter having a group delay that varies significantly with frequency, according to one or more embodiments.

[0027] Figure 6Shows a known method for mixing input signals to create an output signal using a direct mixing matrix and one or more decorrelating mixing matrices, according to one or more embodiments.

[0028] Figure 7 Is a flowchart of an exemplary process for converting a set of frequency-domain input audio signals to a set of frequency-domain output audio signals, according to one or more embodiments.

[0029] Figure 8 Shows a block diagram of a system suitable for implementing the features and processes described with reference to Figures 1 to 7 The features and processes described.

[0030] Like reference numerals used in the various figures indicate like elements. Detailed Description

[0031] In the following embodiments, numerous specific details are set forth to provide a thorough understanding of the various described embodiments. Those of ordinary skill in the art will understand that the various described embodiments may be practiced even without these specific details. In other instances, well-known methods, processes, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the embodiments. Several features will be described below, each of which may be used independently of one another or in any combination with other features.

[0032] Nomenclature

[0033] As used herein, the term "comprising" and its variants will be construed as an open-ended term meaning "including, but not limited to". The term "or" will be construed as "and / or" unless the context clearly dictates otherwise. The term "based on" will be construed as "at least partially based on". The terms "an example implementation" and "example implementation" shall be construed as "at least one example implementation". The term "another implementation" will be construed as "at least one other implementation". The terms "is determined", "determines" will be construed as obtaining, receiving, operating, calculating, estimating, predicting, or deriving. Additionally, in the following description and claims, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains.

[0034] System Overview

[0035] Figure 1Shows a linear mixing system 100 according to one or more embodiments, where a set of input audio signals is filtered to produce a set of audio output signals. For example, the system 100 can be implemented in an audio filter bank. The audio filter bank includes a bank of band-pass filters that separate the input audio signal into multiple frequency sub-bands of the input audio signal. In the example shown, the linear mixing system 100 includes a set of filters 101 and a summer 102. N input signals (X1... X N ) are processed by the filter bank 101 and summed by the summer 102 to produce M output signals (Y1... Y M ). The linear mixing system 100 can be defined in terms of frequency-domain input and frequency-domain output signals as follows:

[0036]

[0037]

[0038] According to Equation [3], the frequency-domain output audio signal Y m (f) (m ∈ [1... M]) is formed as the sum of the filtered frequency-domain input audio signals X n (f), where the contribution of the frequency-domain input audio signal X n (f) (n ∈ [1... N]) to Y m (f) is determined by the composite frequency-domain vector G m,n (f) according to the following equation:

[0039]

[0040] For the purposes of the following discussion, G(f) will be referred to as the exemplary composite frequency-domain gain vector, and this should be understood to refer to any of the composite frequency-domain gain vectors G m,n (f) used in Equations [3] and [4].

[0041] Figure 2 Shows the desired frequency response curve of the filter according to one or more embodiments. The desired frequency response of the exemplary composite frequency-domain gain vector can be generated by a process that creates a smooth function, as Figure 2 shown, where the filter gain 20 as a function of frequency is defined according to a predefined set of control frequencies fc1, fc2... and corresponding component gain values w1, w2.... For example, the gain 21 of the filter at frequency fc2 is set by the component gain value w2, as Figure 2 shown. Figure 2 The frequency response shown in is achieved by the weighted sum of several predefined component frequency-domain gain vectors.

[0042] Figure 3shows a set of filter bank frequency responses according to one or more embodiments, where the response 300H of the reference band 2 0,2 (f). The frequency responses of these predefined component frequency domain gain vectors are hereinafter referred to as the component frequency domain gain vectors H 0,b (f), b ∈ [1...B], where B is the number of frequency bands (e.g., in the Figure 3 example of, B = 5), and each of the component frequency domain gain vectors has an alternative representation in the form of a time-domain impulse response h 0,b (n).

[0043] In an embodiment, the desired filter response (see Figure 2 ) can be formed by a weighted sum of predefined filter bank responses. This can be expressed as a time-domain or frequency-domain summation:

[0044]

[0045] In some implementations, the set of component frequency domain gain vectors is augmented with additional component frequency domain gain vectors H 0,b (f) whose frequency responses are modified to create a decorrelation effect. The augmented set of component frequency domain gain vectors is hereinafter referred to as the decorrelated component frequency domain gain vectors, which are represented by the following nomenclature:

[0046] H l，b (f) b ∈ [1...B], l ∈ [0...L]. [6]

[0047] where B is the number of sub-bands and L is the number of decorrelation functions.

[0048] By applying a modified form of Equation [5] as shown in Equation [7], this augmented set of component frequency domain gain vectors can be used in a filter bank-based audio processing system to generate a composite frequency domain gain vector:

[0049]

[0050] Figure 4 shows the bandpass response of a typical component frequency domain gain vector according to one or more embodiments. In the example shown, the component frequency domain gain vector H 0,b (f) has an amplitude response 401 that typically dominates within a specific sub-band range of the total frequency range, and the group delay 402 is substantially constant within the sub-band range. When a filter is used to process an audio signal, the group delay is considered to be substantially constant if the fluctuations in the group delay are small enough to be perceptually insignificant to the listener.

[0051] Figure 5Shows the frequency response of a sub - band filter having a group delay that varies significantly with frequency according to one or more embodiments. The frequency response of the decorrelation component frequency - domain gain vectors (such as H l,b (f)(l≠0)) exhibits a group delay 502 that varies within the sub - band frequency range, and the variation in the group delay is such that an input audio signal filtered by the decorrelation component frequency - domain gain vector H l,b (f)(l≠0) is perceived as being decorrelated from an input audio signal filtered by the component frequency - domain gain vector H 0,b (f).

[0052] In the art, it is known how to create a frequency response having a varying group delay that varies over a wide frequency range for the purpose of creating a perceived decorrelation effect. In one embodiment, a known decorrelation frequency response can be adjusted by applying an amplitude response 501 to form a decorrelation component frequency - domain gain vector. In one embodiment, a known decorrelation function D l (f)(l∈[1...L]) is used to calculate a set of B decorrelation component frequency - domain gain vectors:

[0053] H l，b (f) = D l X H 0，b (f)(b∈[1...B]). [8]

[0054] Figure 6 Shows a system 600 for mixing input signals using a direct mixing matrix and one or more decorrelation mixing matrices to produce an output signal according to one or more embodiments. Given a set of L known decorrelation functions D l (f)(l∈[1...L]), an N - channel input signal (X) is processed by the system 600 to produce an M - channel output signal (Y). In this example, the processing for one sub - band (e.g., band b) is shown, where the N - channel input 601 (X) is applied to a direct linear mixing matrix 602 (C) (e.g., an M×N matrix) to produce an M - channel direct signal 603. The N - channel input 601 is also processed by a linear mixer 610 (Q l )(e.g., a K L ×N matrix) to produce a set of K L channels 611, which are passed through a set of K L decorrelation filters 612 (D l ), each decorrelation filter applying a frequency response D L (f) to produce K L channel signals 613, and the K L channel signals 613 are then processed by a linear mixer 614 (P l )(e.g., an M×K LThe matrix) is remixed to produce M-channel decorrelated component signals 615. Then, the M-channel direct signals 603 are summed with the M-channel decorrelated component signals (e.g., the decorrelated component signals (615)) to produce M-channel outputs 602 (Y).

[0055] In this embodiment, by using a single set of weighting coefficients to replace the functions of the linear mixing matrices C, Q1...Q L and P1...P L and is implemented Figure 6 An alternative to the processing shown. According to one embodiment, and referring back to Equation [4], the output channel Y m (f) can be generated according to the following:

[0056]

[0057]

[0058] Equation [9] can be implemented in a filter bank-based audio processing system, where the number of filters is (L + 1) x B, rather than the B filters known to be used in the art. This expanded filter bank can be further regarded as the B filters known previously, and an additional L x B filters corresponding to L different decorrelation functions.

[0059] In some embodiments, Equation [9] is implemented as an audio filter bank that includes a converter (e.g., a fast Fourier transform) configured to convert a set of time-domain input audio signals into a set of frequency-domain input audio signals X n (f), and a linear mixer (performing matrix multiplication operations) configured to implement to convert the set of frequency-domain input audio signals X n (f) into a set of frequency-domain output audio signals Y m (f). Each frequency-domain output audio signal is the sum of the filtered frequency-domain input audio signals, and each filter used to filter the frequency-domain input audio signals is characterized by a complex gain function within the corresponding sub-band frequency range of the frequency-domain input audio signals. The contribution of the frequency-domain input audio signals to the frequency-domain output audio signals is determined by a composite frequency-domain gain vector.

[0060] In some embodiments, Equation [9] is implemented as an audio filter bank system that includes a converter (e.g., a fast Fourier transform) configured to convert a set of time-domain input audio signals into a set of frequency-domain input audio signals X n (f), and configured to implement to convert the set of frequency-domain input audio signals X n(f) is converted into a set of frequency-domain output audio signals Y m The linear mixer of (f) (software and hardware for implementing the summation of product operations). The linear mixer includes weighting coefficients (element G m,n (f)) that provide a frequency-dependent gain function, which includes a direct component defined as a frequency-dependent gain and one or more decorrelating components having a group phase response that varies with frequency. The frequency-dependent gain is formed by a set of sub-band functions, where each sub-band function is formed by a set of corresponding component transfer functions that include a direct component and one or more decorrelating components.

[0061] Example process

[0062] Figure 7 is a flowchart of an exemplary process 700 for converting a set of frequency-domain input audio signals into a set of frequency-domain output audio signals according to one or more embodiments. Process 700 may be implemented, for example, by the system 800 described with reference to Figure 8 described.

[0063] Process 700 calculates each frequency-domain output audio signal as the sum of filtered frequency-domain input audio signals, where each filtered frequency-domain input audio signal defines a complex gain function over a corresponding sub-band frequency range, and the contribution of the frequency-domain input audio signal to the frequency-domain output audio signal is determined by a composite frequency-domain gain vector (701).

[0064] Process 700 continues by obtaining a composite frequency-domain gain vector by calculating a set of component frequency-domain gain vectors (702). At least one of the component frequency-domain gain vectors is a decorrelating component frequency-domain gain vector formed by enhancing a component frequency-domain gain vector with an additional component frequency-domain gain vector having a modified frequency response to create a decorrelating effect.

[0065] Process 700 continues by summing the component frequency-domain gain vectors to form a composite frequency-domain gain vector (703).

[0066] Example system architecture

[0067] Figure 8 shows a block diagram of an example system 800 suitable for implementing the embodiments of the present disclosure. System 800 includes one or more server computers or any client device, including but not limited to: call servers, user equipment, conference room systems, home theater systems, virtual reality (VR) devices, and immersive content capture devices. System 800 includes any consumer device, including but not limited to: smart phones, tablet computers, wearable computers, in-vehicle computers, game consoles, surround sound systems, information kiosks, etc.

[0068] As shown in the figure, system 800 includes a central processing unit (CPU) 801, which is capable of executing various processes according to a program stored in, for example, a read-only memory (ROM) 802 or a program loaded into a random access memory (RAM) 803 from, for example, a storage unit 808. In the RAM 803, data required when the CPU 801 executes various processes is also stored as needed. The CPU 801, ROM 802, and RAM 803 are connected to each other via a bus 804. An input / output (I / O) interface 805 is also connected to the bus 804.

[0069] The following components are connected to the I / O interface 805: an input unit 806, which may include a keyboard, a mouse, or the like; an output unit 807, which may include a display such as a liquid crystal display (LCD) and one or more speakers; a storage unit 808, which includes a hard disk or another suitable storage device; and a communication unit 809, which includes a network interface such as a network card (e.g., wired or wireless).

[0070] In some implementations, the input unit 806 includes one or more microphones at different positions (depending on the host device) capable of acquiring audio signals in various formats (e.g., mono, stereo, spatial, immersive, and other suitable formats).

[0071] In some implementations, the output unit 807 includes a system with various numbers of speakers. The output unit 807 can present audio signals in various formats (e.g., mono, stereo, immersive, binaural, and other suitable formats) depending on the capabilities of the host device.

[0072] The communication unit 809 is configured to communicate with other devices (e.g., via a network). A driver 810 is also connected to the I / O interface 805 as needed. A removable medium 811 (e.g., a disk, an optical disc, a magneto-optical disc, a flash drive, or another suitable removable medium) is installed on the driver 810 so that a computer program read from it is installed into the storage unit 808 as needed. Those skilled in the art will understand that although the system 800 is described as including the above components, in practical applications, some of these components can be added, removed, and / or replaced, and all such modifications or changes fall within the scope of the present disclosure.

[0073] According to an exemplary embodiment of the present disclosure, the processes described above can be implemented as a computer software program or implemented on a computer-readable storage medium. For example, an embodiment of the present disclosure includes a computer program product that includes a computer program tangibly embodied on a machine-readable medium, the computer program including program code for performing a method. In such an embodiment, the computer program can be downloaded and installed from a network via the communication unit 809, and / or installed from the removable medium 811, as inFigure 8 as shown in

[0074] Generally, various example embodiments of the present invention may be implemented in hardware or in special-purpose circuitry (e.g., control circuitry), software, logic, or any combination thereof. For example, the units discussed above may be executed by control circuitry (e.g., a CPU combined with Figure 8 other components of), and thus, the control circuitry may perform the actions described in the present disclosure. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software executable by a controller, microprocessor, or other computing device (e.g., control circuitry). Although various aspects of the example embodiments of the present disclosure are shown and described as block diagrams, flowcharts, or using some other graphical representation, it should be understood that, as a non-limiting example, the blocks, apparatus, systems, techniques, or methods described herein may be implemented in hardware, software, firmware, special-purpose circuitry or logic, general-purpose hardware or controllers, or other computing devices, or some combination thereof.

[0075] Additionally, the various blocks shown in the flowcharts may be regarded as method steps, and / or operations resulting from operations of computer program code, and / or as multiple coupled logic circuit elements configured to perform the associated one or more functions. For example, embodiments of the present disclosure include a computer program product that includes a computer program tangibly embodied on a machine-readable medium, the computer program containing program code configured to perform the methods described above.

[0076] In the context of the present disclosure, a machine / computer-readable medium may be any tangible medium that can contain or store a program for use by or in connection with an instruction execution system, apparatus, or device. A machine / computer-readable medium may be a machine / computer-readable signal medium or a machine / computer-readable storage medium. A machine / computer-readable medium may be non-transitory and may include (but is not limited to) electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination of the foregoing. More specific examples of a machine / computer-readable storage medium would include: an electrical connection having one or more wires; a portable computer diskette; a hard disk; a RAM; a ROM; an erasable programmable read-only memory (EPROM or Flash memory); an optical fiber; a portable compact disc read-only memory (CD-ROM); an optical storage device; a magnetic storage device; or any suitable combination of the foregoing.

[0077] Computer program code for performing the methods of the present disclosure may be written in any combination of one or more programming languages. Such computer program code may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing device having control circuitry, such that when executed by the processor of the computer or other programmable data processing device, the program code causes the functions / operations specified in the flowchart and / or block diagram to be implemented. The program code may be executed entirely on the computer, partly on the computer (as a stand-alone software package), partly on the computer and partly on a remote computer, or entirely on the remote computer or server or distributed among one or more remote computers and / or servers.

[0078] Although this document contains many specific implementation details, these details should not be regarded as limitations on the scope of the claimed invention, but rather as descriptions of features specific to particular embodiments. Certain features described in the context of separate embodiments in this specification may also be implemented in combination in a single embodiment. Conversely, the various features described in the context of a single embodiment may also be implemented separately or in any suitable sub-combination in multiple embodiments. In addition, although the features may be described above as acting in a particular combination and even initially claimed as such, in some cases, one or more features from the claimed combination may be excluded from the combination, and the claimed combination may be directed to a sub-combination or a variation of the sub-combination. The logical flow depicted in the figures does not necessarily require the particular order shown or sequential order to achieve the desired result. Additionally, other steps may be provided, or steps may be eliminated from the described flow, and other components may be added to the described system or other components removed from the described system. Accordingly, other embodiments are also within the scope of the following claims.

Claims

1. A method for converting a set of frequency-domain input audio signals into a set of frequency-domain output audio signals, the method comprising: using one or more processors to calculate the sum of the filtered frequency-domain input audio signals as the respective frequency-domain output audio signals, wherein each filter for filtering the frequency-domain input audio signals is characterized by a complex gain function over a corresponding sub-band frequency range of the frequency-domain input audio signals, wherein the contribution of the frequency-domain input audio signals to the frequency-domain output audio signals is determined by a composite frequency-domain gain vector, and the composite frequency-domain gain vector is obtained by: using the one or more processors to calculate a set of component frequency-domain gain vectors, wherein at least one of the set of component frequency-domain gain vectors is a decorrelated component frequency-domain gain vector formed by enhancing the component frequency-domain gain vector with an additional component frequency-domain gain vector having a modified frequency response to create a decorrelation effect; and using the one or more processors to sum the set of component frequency-domain gain vectors to form the composite frequency-domain gain vector.

2. A system, comprising: one or more processors; and a non-transitory computer-readable medium storing instructions that, when executed by the one or more processors, cause the one or more processors to perform the method of claim 1.

3. A non-transitory computer-readable medium storing instructions that, when executed by one or more processors, cause the one or more processors to perform the method of claim 1.

4. A computer program product comprising instructions that, when executed by one or more processors, cause the one or more processors to perform the method of claim 1.

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