Stereo separation and directional suppression with omni-directional microphones

Systems and methods for stereo separation and directional suppression are provided. An example method includes receiving a first audio signal, representing sound captured by a first microphone associated with a first location, and a second audio signal, representing sound captured by a second microphone associated with a second location. The microphones comprise omni-directional microphones. The distance between the first and second microphones is limited by the size of a mobile device. A first channel signal of a stereo signal is generated by forming, based on the first and second audio signals, a first beam at the first location. A second channel signal of the stereo signal is generated by forming, based on the first and second audio signals, a second beam at the second location. First and second directions, associated respectively with the first and second beams, are fixed relative to a line between the first and second locations.

FIELD

The present invention relates generally to audio processing, and, more specifically, to systems and methods for stereo separation and directional suppression with omni-directional microphones.

BACKGROUND

Recording stereo audio with a mobile device, such as smartphones and tablet computers, may be useful for making video of concerts, performances, and other events. Typical stereo recording devices are designed with either large separation between microphones or with precisely angled directional microphones to utilize acoustic properties of the directional microphones to capture stereo effects. Mobile devices, however, are limited in size and, therefore, the distance between microphones is significantly smaller than a minimum distance required for optimal omni-directional microphone stereo separation. Using directional microphones is not practical due to the size limitations of the mobile devices and may result in an increase in overall costs associated with the mobile devices. Additionally, due to the limited space for placing directional microphones, a user of the mobile device can be a dominant source for the directional microphones, often interfering with target sound sources.

Another aspect of recording stereo audio using a mobile device is a problem of capturing acoustically representative signals to be used in subsequent processing. Traditional microphones used for mobile devices may not able to handle high pressure conditions in which stereo recording is performed, such as a performance, concert, or a windy environment. As a result, signals generated by the microphones can become distorted due to reaching their acoustic overload point (AOP).

SUMMARY

Provided are systems and methods for stereo separation and directional suppression with omni-directional microphones. An example method includes receiving at least a first audio signal and a second audio signal. The first audio signal can represent sound captured by a first microphone associated with a first location. The second audio signal can represent sound captured by a second microphone associated with a second location. The first microphone and the second microphone can include omni-directional microphones. The method can include generating a first channel signal of a stereo audio signal by forming, based on the at least first audio signal and second audio signal, a first beam at the first location. The method can also include generating a second channel signal of the stereo audio signal by forming, based on the at least first audio signal and second audio signal, a second beam at the second location.

In some embodiments, a distance between the first microphone and the second microphone is limited by a size of a mobile device. In certain embodiments, the first microphone is located at the top of the mobile device and the second microphone is located at the bottom of the mobile device. In other embodiments, the first and second microphones (and additional microphones, if any) may be located differently, including but not limited to, the microphones being located along a side of the device, e.g., separated along the side of a tablet having microphones on the side.

In some embodiments, directions of the first beam and the second beam are fixed relative to a line between the first location and the second location. In some embodiments, the method further includes receiving at least one other acoustic signal. The other acoustic signal can be captured by another microphone associated with another location. The other microphone includes an omni-directional microphone. In some embodiments, forming the first beam and the second beam is further based on the other acoustic signal. In some embodiments, the other microphone is located off the line between the first microphone and the second microphone.

In some embodiments, forming the first beam includes reducing signal energy of acoustic signal components associated with sources outside the first beam. Forming the second beam can include reducing signal energy of acoustic signal components associated with further sources off the second beam. In certain embodiments, reducing signal energy is performed by a subtractive suppression. In some embodiments, the first microphone and the second microphone include microphones having an acoustic overload point (AOP) greater than a pre-determined sound pressure level. In certain embodiments, the pre-determined sound pressure level is 120 decibels.

According to another example embodiment of the present disclosure, the steps of the method for stereo separation and directional suppression with omni-directional microphones are stored on a machine-readable medium comprising instructions, which when implemented by one or more processors perform the recited steps.

Other example embodiments of the disclosure and aspects will become apparent from the following description taken in conjunction with the following drawings.

DETAILED DESCRIPTION

The technology disclosed herein relates to systems and methods for stereo separation and directional suppression with omni-directional microphones. Embodiments of the present technology may be practiced with audio devices operable at least to capture and process acoustic signals. In some embodiments, the audio devices may be hand-held devices, such as wired and/or wireless remote controls, notebook computers, tablet computers, phablets, smart phones, personal digital assistants, media players, mobile telephones, and the like. The audio devices can have radio frequency (RF) receivers, transmitters and transceivers; wired and/or wireless telecommunications and/or networking devices; amplifiers; audio and/or video players; encoders; decoders; speakers; inputs; outputs; storage devices; and user input devices. Audio devices may have input devices such as buttons, switches, keys, keyboards, trackballs, sliders, touch screens, one or more microphones, gyroscopes, accelerometers, global positioning system (GPS) receivers, and the like. The audio devices may have outputs, such as LED indicators, video displays, touchscreens, speakers, and the like.

In various embodiments, the audio devices operate in stationary and portable environments. The stationary environments can include residential and commercial buildings or structures and the like. For example, the stationary embodiments can include concert halls, living rooms, bedrooms, home theaters, conference rooms, auditoriums, business premises, and the like. Portable environments can include moving vehicles, moving persons or other transportation means, and the like.

According to an example embodiment, a method for stereo separation and directional suppression includes receiving at least a first audio signal and a second audio signal. The first audio signal can represent sound captured by a first microphone associated with a first location. The second audio signal can represent sound captured by a second microphone associated with a second location. The first microphone and the second microphone can comprise omni-directional microphones. The example method includes generating a first stereo signal by forming, based on the at least first audio signal and second audio signal, a first beam at the first location. The method can further include generating a second stereo signal by forming, based on the at least first audio signal and second audio signal, a second beam at the second location.

FIG. 1is a block diagram of an example environment100in which the embodiments of the present technology can be practiced. The environment100ofFIG. 1can include audio device104and audio sources112,114, and116. The audio device can include at least a primary microphone106aand a secondary microphone106b.

The primary microphone106aand the secondary microphone106bof the audio device104may comprise omni-directional microphones. In some embodiments, the primary microphone106ais located at the bottom of the audio device104and, accordingly, may be referred to as the bottom microphone. Similarly, in some embodiments, the secondary microphone106bis located at the top of the audio device104and, accordingly, may be referred to as the top microphone. In other embodiments, the first and second microphones (and additional microphones, if any) may be located differently, including but not limited to, the microphones being located along a side of the device, e.g., separated along the side of a tablet having microphones on the side.

Some embodiments if the present disclosure utilize level differences (e.g., energy differences), phase differences, and differences in arrival times between the acoustic signals received by the two microphones106aand106b. Because the primary microphone106ais closer to the audio source112than the secondary microphone106b, the intensity level, for the audio signal from audio source112(represented graphically by122, which may also include noise in addition to desired sounds) is higher for the primary microphone106a, resulting in a larger energy level received by the primary microphone106a. Similarly, because the secondary microphone106bis closer to the audio source116than the primary microphone106a, the intensity level, for the audio signal from audio source116(represented graphically by126, which may also include noise in addition to desired sounds) is higher for the secondary microphone106, resulting in a larger energy level received by the secondary microphone106b. On the other hand, the intensity level for the audio signal from audio source114(represented graphically by124, which may also include noise in addition to desired sounds) could be higher for one of the two microphones106aand106b, depending on, for example, its location within cones108aand108b.

The level differences can be used to discriminate between speech and noise in the time-frequency domain. Some embodiments may use a combination of energy level differences and differences in arrival times to discriminate between acoustic signals coming from different directions. In some embodiments, a combination of energy level differences and phase differences is used for directional audio capture.

Various example embodiments of the present technology utilize level differences (e.g. energy differences), phase differences, and differences in arrival times for stereo separation and directional suppression of acoustic signals captured by microphones106aand106b. As shown inFIG. 1, a multi-directional acoustic signal provided by audio sources112,114, and116can be separated into a left channel signal of a stereo audio signal and a right channel signal of the stereo audio signal (also referred to herein as left and right stereo signals, or left and right channels of the stereo signal). The left channel of the stereo signal can be obtained by focusing on acoustic signals within cone118aand suppressing acoustic signals outside the cone118a. The cone118acan cover audio sources112and114. Similarly, a right channel of the stereo signal can be obtained by focusing on acoustic signals within cone118band suppressing acoustic signals outside cone118b. The cone118bcan cover audio sources114and116. In some embodiments of the present disclosure, audio signals coming from a site associated with user510(also referred to as narrator/user510) are suppressed in both the left channel of the stereo signal and the right channel of the stereo signal. Various embodiments of the present technology can be used for capturing stereo audio when shooting video at home, during concerts, school plays, and so forth.

FIG. 2is a block diagram of an example audio device. In some embodiments, the example audio device ofFIG. 2provides additional details for audio device104ofFIG. 1. In the illustrated embodiment, the audio device104includes a receiver210, a processor220, the primary microphone106a, a secondary microphone106b, an audio processing system230, and an output device240. In some embodiments, the audio device104includes another, optional tertiary microphone106c. The audio device104may include additional or different components to enable audio device104operations. Similarly, the audio device104may include fewer components that perform similar or equivalent functions to those depicted inFIG. 2.

Processor220may execute instructions and modules stored in a memory (not illustrated inFIG. 2) of the audio device104to perform functionality described herein, including noise reduction for an acoustic signal. Processor220may include hardware and software implemented as a processing unit, which may process floating point and/or fixed point operations and other operations for the processor220.

The example receiver210can be a sensor configured to receive a signal from a communications network. In some embodiments, the receiver210may include an antenna device. The signal may then be forwarded to the audio processing system230for noise reduction and other processing using the techniques described herein. The audio processing system230may provide a processed signal to the output device240for providing an audio output(s) to the user. The present technology may be used in one or both of the transmitting and receiving paths of the audio device104.

The audio processing system230can be configured to receive acoustic signals that represent sound from acoustic source(s) via the primary microphone106aand secondary microphone106band process the acoustic signals. The processing may include performing noise reduction for an acoustic signal. The example audio processing system230is discussed in more detail below. The primary and secondary microphones106a,106bmay be spaced a distance apart in order to allow for detecting an energy level difference, time arrival difference, or phase difference between them. The acoustic signals received by primary microphone106aand secondary microphone106bmay be converted into electrical signals (e.g., a primary electrical signal and a secondary electrical signal). The electrical signals may, in turn, be converted by an analog-to-digital converter (not shown) into digital signals, that represent the captured sound, for processing in accordance with some embodiments.

The output device240can include any device which provides an audio output to the user. For example, the output device240may include a loudspeaker, an earpiece of a headset or handset, or a memory where the output is stored for video/audio extraction at a later time, e.g., for transfer to computer, video disc or other media for use.

In various embodiments, where the primary and secondary microphones include omni-directional microphones that are closely-spaced (e.g., 1-2 cm apart), a beamforming technique may be used to simulate forward-facing and backward-facing directional microphones. The energy level difference may be used to discriminate between speech and noise in the time-frequency domain used in noise reduction.

FIG. 3is a block diagram of an example audio processing system. The block diagram ofFIG. 3provides additional details for the audio processing system230of the example block diagram ofFIG. 2. Audio processing system230in this example includes various modules including fast cochlea transform (FCT)302and304, beamformer310, multiplicative gain expansion320, reverb330, mixer340, and zoom control350.

FCT302and304may receive acoustic signals from audio device microphones and convert the acoustic signals into frequency range sub-band signals. In some embodiments, FCT302and304are implemented as one or more modules operable to generate one or more sub-band signals for each received microphone signal. FCT302and304can receive an acoustic signal representing sound from each microphone included in audio device104. These acoustic signals are illustrated as signals X1-XI, wherein X1represent a primary microphone signal and Xirepresents the rest (e.g., N−1) of the microphone signals. In some embodiments, the audio processing system230ofFIG. 3performs audio zoom on a per frame and per sub-band basis.

In some embodiments, beamformer310receives frequency sub-band signals as well as a zoom indication signal. The zoom indication signal can be received from zoom control350. The zoom indication signal can be generated in response to user input, analysis of a primary microphone signal, or other acoustic signals received by audio device104, a video zoom feature selection, or some other data. In operation, beamformer310receives sub-band signals, processes the sub-band signals to identify which signals are within a particular area to enhance (or “zoom”), and provide data for the selected signals as output to multiplicative gain expansion module320. The output may include sub-band signals for the audio source within the area to enhance. Beamformer310can also provide a gain factor to multiplicative gain expansion320. The gain factor may indicate whether multiplicative gain expansion320should perform additional gain or reduction to the signals received from beamformer310. In some embodiments, the gain factor is generated as an energy ratio based on the received microphone signals and components. The gain indication output by beamformer310may be a ratio of energy in the energy component of the primary microphone reduced by beamformer310to output energy of beamformer310. Accordingly, the gain may include a boost or cancellation gain expansion factor. An example gain factor is discussed in more detail below.

Beamformer310can be implemented as a null processing noise subtraction (NPNS) module, multiplicative module, or a combination of these modules. When an NPNS module is used in microphones to generate a beam and achieve beamforming, the beam is focused by narrowing constraints of alpha (α) and gamma (σ). Accordingly, a beam may be manipulated by providing a protective range for the preferred direction. Exemplary beamformer310modules are further described in U.S. patent application Ser. No. 14/957,447, entitled “Directional Audio Capture,” and U.S. patent application Ser. No. 12/896,725, entitled “Audio Zoom” (issued as U.S. Pat. No. 9,210,503 on Dec. 8, 2015), the disclosures of which is incorporated herein by reference in its entirety. Additional techniques for reducing undesired audio components of a signal are discussed in U.S. patent application Ser. No. 12/693,998, entitled “Adaptive Noise Reduction Using Level Cues” (issued as U.S. Pat. No. 8,718,290 on May 6, 2014), the disclosure of which is incorporated herein by reference in its entirety.

Multiplicative gain expansion module320can receive sub-band signals associated with audio sources within the selected beam, the gain factor from beamformer310, and the zoom indicator signal. Multiplicative gain expansion module320can apply a multiplicative gain based on the gain factor received. In effect, multiplicative gain expansion module320can filter the beamformer signal provided by beamformer310.

The gain factor may be implemented as one of several different energy ratios. For example, the energy ratio may include a ratio of a noise reduced signal to a primary acoustic signal received from a primary microphone, the ratio of a noise reduced signal and a detected noise component within the primary microphone signal, the ratio of a noise reduced signal and a secondary acoustic signal, or the ratio of a noise reduced signal compared to an intra level difference between a primary signal and a further signal. The gain factors may be an indication of signal strength in a target direction versus all other directions. In other words, the gain factor may be indicative of multiplicative expansions and whether these additional expansions should be performed by the multiplicative gain expansion320. Multiplicative gain expansion320can output the modified signal and provide signal to reverb330(also referred to herein as reverb (de-reverb)330).

Reverb330can receive the sub-band signals output by multiplicative gain expansion320, as well as the microphone signals also received by beamformer310, and perform reverberation (or dereverberation) of the sub-band signal output by multiplicative gain expansion320. Reverb330may adjust a ratio of direct energy to remaining energy within a signal based on the zoom control indicator provided by zoom control350. After adjusting the reverberation of the received signal, reverb330can provide the modified signal to a mixing component, e.g., mixer340.

The mixer340can receive the reverberation adjusted signal and mix the signal with the signal from the primary microphone. In some embodiments, mixer340increases the energy of the signal appropriately when audio is present in the frame and decreases the energy when there is little audio energy present in the frame.

FIG. 4is a block diagram illustrating an audio processing system400, according to another example embodiment. The audio processing system400can include audio zoom audio (AZA), a subsystem augmented with a source estimation subsystem430. The example AZA subsystem includes limiters402a,402b, and402c, along with various other modules including FCT404a,404b, and404c, analysis406, zoom control410, signal modifier412, plus variable amplifier418and a limiter420. The source estimation subsystem430can include a source direction estimator (SDE)408(also referred to variously as SDE module408or as a target estimator), a gain (module)416, and an automatic gain control (AGC) (module)414. In various embodiments, the audio processing system400processes acoustic audio signal from microphones106a,106b, and optionally a third microphone,106c.

In various embodiments, SDE module408is operable to localize a source of sound. The SDE module408is operable to generate cues based on correlation of phase plots between different microphone inputs. Based on the correlation of the phase plots, the SDE module408is operable to compute a vector of salience estimates at different angles. Based on the salience estimates, the SDE module408can determine a direction of the source. In other words, a peak in the vector of salience estimates is an indication of direction of a source in a particular direction. At the same time, sources of diffused nature, i.e., non-directional, are represented by poor salience estimates at all the angles. The SDE module408can rely upon the cues (estimates of salience) to improve the performance of a directional audio solution, which is carried out by the analysis module406, signal modifier412, and zoom control410. In some embodiments, the signal modifier412includes modules analogous or similar to beamformer310, multiplicative gain expansion module320, reverb module330, and mixer module340as shown for audio system230inFIG. 3.

In some embodiments, estimates of salience are used to localize the angle of the source in the range of 0 to 360 degrees in a plane parallel to the ground, when, for example, the audio device104is placed on a table top. The estimates of salience can be used to attenuate/amplify the signals at different angles as required by the customer. The characterization of these modes may be driven by a SDE salience parameter. Example AZA and SDE subsystems are described further in U.S. patent application Ser. No. 14/957,447, entitled “Directional Audio Capture,” the disclosure of which is incorporated herein by reference in its entirety.

FIG. 5Aillustrates an example environment500for directional audio signal capture using two omni-directional microphones. The example environment500can include audio device104, primary microphone106a, secondary microphone106b, a user510(also referred to as narrator510) and a second sound source520(also referred to as scene520). Narrator510can be located proximate to primary microphone106a. Scene520can be located proximate to secondary microphone106b. The audio processing system400may provide a dual output including a first signal and a second signal. The first signal can be obtained by focusing on a direction associated with narrator510. The second signal can be obtained by focusing on a direction associated with scene520. SDE module408(an example of which is shown inFIG. 4) can provide a vector of salience estimates to localize a direction associated with target sources, for example narrator510and scene520.FIG. 5Billustrates a directional audio signal captured using two omni-directional microphones. As target sources or audio device change positions, SDE module408(e.g., in the system inFIG. 4) can provide an updated vector of salience estimates to allow audio processing system400to keep focusing on the target sources.

FIG. 6shows a block diagram of an example NPNS module600. The NPNS module600can be used as a beamformer module in audio processing systems230or400. NPNS module600can include analysis modules602and606(e.g., for applying coefficients σ1and σ2respectively), adaptation modules604and608(e.g., for adapting the beam based on coefficients α1 and α2) and summing modules610,612, and614. The NPNS module600may provide gain factors based on inputs from a primary microphone, a secondary microphone, and, optionally, a tertiary microphone. Exemplary NPNS modules are further discussed in U.S. patent application Ser. No. 12/215,980, entitled “System and Method for Providing Noise Suppression Utilizing Null Processing Noise Subtraction” (issued as U.S. Pat. No. 9,185,487 on Nov. 10, 2015), the disclosure of which is incorporated herein by reference in its entirety.

In the example inFIG. 6, the NPNS module600is configured to adapt to a target source. Attenuation coefficients σ1and σ2can be adjusted based on a current direction of a target source as either the target source or the audio device moves.

FIG. 7Ashows an example coordinate system710used for determining the source direction in the AZA subsystem. Assuming that the largest side of the audio device104is parallel to the ground when, for example, the audio device104is placed on a table top, X axis of coordinate system710is directed from the bottom to the top of audio device104. Y axis of coordinate system710is directed in such a way that XY plane is parallel to the ground.

In various embodiments of the present disclosure, the coordinate system710used in AZA is rotated to adapt for providing a stereo separation and directional suppression of received acoustic signals.FIG. 7Bshows a rotated coordinate system720as related to audio device104. The audio device104is oriented in such way that the largest side of the audio device is orthogonal (e.g., perpendicular) to the ground and the longest edge of the audio device is parallel to the ground when, for example, the audio device104is held when recording a video. The X axis of coordinate system720is directed from the top to the bottom of audio device104. The Y axis of coordinate system720is directed in such a way that XY plane is parallel to the ground.

According to various embodiments of the present disclosure, at least two channels of a stereo signal (also referred to herein as left and right channel stereo (audio) signals, and a left stereo signal and a right stereo signal) are generated based on acoustic signals captured by two or more omni-directional microphones. In some embodiments, the omni-directional microphones include the primary microphone106aand the secondary microphone106b. As shown inFIG. 1, the left (channel) stereo signal can be provided by creating a first target beam on the left. The right (channel) stereo signal can be provided by creating a second target beam on the right. According to various embodiments, the directions for the beams are fixed and maintained as a target source or audio device changes position. Fixing the directions for the beams allows obtaining a natural stereo effect (having left and right stereo channels) that can be heard by a user. By fixing the direction, the natural stereo effect can be heard when an object moves across the field of view, from one side to the other, for example, a car moving across a movie screen. In some embodiments, the directions for the beams are adjustable but are maintained fixed during beamforming.

According to some embodiments of the present disclosure, NPNS module600(in the example inFIG. 6) is modified so it does not adapt to a target source. A modified NPNS module800is shown inFIG. 8. Components of NPNS module800are analogous to elements of NPNS module600except that the modules602and606inFIG. 6are replaced with modules802and806. Unlike in the example inFIG. 6, values for coefficients σ1and σ2in the example embodiment inFIG. 8are fixed during forming the beams for creation of stereo signals. By preventing adaptation to the target source, the direction for beams remains fixed, ensuring that the left stereo signal and the right stereo signal do not overlap as sound source(s) or the audio device change position. In some embodiments, the attenuation coefficients σ1and σ2are determined by calibration and tuning.

FIG. 9is an example environment900, in which example methods for stereo separation and directional suppression can be implemented. The environment900includes audio device104and audio sources910,920, and930. In some embodiments, the audio device104includes two omni-directional microphones106aand106b. The primary microphone106ais located at the bottom of the audio device104and the secondary microphone106bis located at the top of the audio device104, in this example. When the audio device104is oriented to record video, for example, in the direction of audio source910, the audio processing system of the audio device may be configured to operate in a stereo recording mode. A left channel stereo signal and a right channel stereo signal may be generated based on inputs from two or more omni-directional microphones by creating a first target beam for audio on the left and a second target beam for audio on the right. The directions for the beams are fixed, according to various embodiments.

In certain embodiments, only two omni-directional microphones106aand106bare used for stereo separation. Using two omni-directional microphones106aand106b, one on each end of the audio device, a clear separation between the left side and the right side can be achieved. For example, the secondary microphone106bis closer to the audio source920(at the right in the example inFIG. 9) and receives the wave from the audio source920shortly before the primary microphone106a. The audio source can be then triangulated based on the spacing between the microphones106aand106band the difference in arrival times at the microphones106aand106b. However, this exemplary two-microphone system may not distinguish between acoustic signals coming from a scene side (where the user is directing the camera of audio device) and acoustic signals coming from the user side (e.g., opposite the scene side). In the example embodiment shown inFIG. 9, the audio sources910and930are equidistant from microphones106aand106b. From the top view of an audio device104, the audio source910is located in front of the audio device104at scene side and the audio source930is located behind the audio device at the user side. The microphones106aand106breceive the same acoustic signal from the audio source910and the same acoustic signal from audio source930since there is no delay in the time of arrival between the microphones, in this example. This means that, when using only the two microphones106aand106b, locations of audio sources910and930cannot be distinguished, in this example. Thus, for this example, it cannot be determined which of the audio sources910and930is located in front and which of the audio sources910and930is located behind the audio device.

In some embodiments, an appropriately-placed third microphone can be used to improve differentiation of the scene (audio device camera's view) direction from the direction behind the audio device. Using a third microphone (for example, the tertiary microphone106cshown inFIG. 9) may help providing a more robust stereo sound. Input from the third microphone can also allow for better attenuation of unwanted content such as speech of the user holding the audio device and people behind the user. In various embodiments, the three microphones106a,106b, and106care not all located in a straight line, so that various embodiments can provide a full 360 degree picture of sounds relative to a plane on which the three microphones are located.

In some embodiments, the microphones106a,106b, and106cinclude high AOP microphones. The AOP microphones can provide robust inputs for beamforming in loud environments, for example, concerts. Sound levels at some concerts are capable of exceeding 120 dB with peak levels exceeding 120 dB considerably. Traditional omni-directional microphones may saturate at these sound levels making it impossible to recover any signal captured by the microphone. High AOP microphones are designed for a higher overload point as compared to traditional microphones and, therefore, are capable of capturing an accurate signal under significantly louder environments when compared to traditional microphones. Combining the technology of high AOP microphones with the methods for stereo separation and directional suppression using omni-directional microphones (e.g., using high AOP omni-directional microphones for the combination) according to various embodiments of the present disclosure, can enable users to capture a video providing a much more realistic representation of their experience during, for example, a concert.

FIG. 10shows a depiction1000of example plots of example directional audio signals. Plot1010represents an unprocessed directional audio signal captured by a secondary microphone106b. Plot1020represents an unprocessed directional audio signal captured by a primary microphone106a. Plot1030represents a right channel stereo audio signal obtained by forming a target beam on the right. Plot1040represents a left channel stereo audio signal obtained by forming a target beam on the left. Plots1030and1040, in this example, show a clear stereo separation of the unprocessed audio signal depicted in plots1010and1020.

FIG. 11is a flow chart showing steps of a method for stereo separation and directional suppression, according to an example embodiment. Method1100can commence, in block1110, with receiving at least a first audio signal and a second audio signal. The first audio signal can represent sound captured by a first microphone associated with a first location. The second audio signal can represent sound captured by a second microphone associated with a second location. The first microphone and the second microphone may comprise omni-directional microphones. In some embodiments, the first microphone and the second microphone comprise microphones with high AOP. In some embodiments, the distance between the first and the second microphones is limited by size of a mobile device.

In block1120, a first stereo signal (e.g., a first channel signal of a stereo audio signal) can be generated by forming a first beam at the first location, based on the first audio signal and the second audio signal. In block1130, a second stereo signal (e.g., a second channel signal of the stereo audio signal) can be generated by forming a second beam at the second location based on the first audio signal and the second audio signal.

FIG. 12illustrates an example computer system1200that may be used to implement some embodiments of the present invention. The computer system1200ofFIG. 12may be implemented in the contexts of the likes of computing systems, networks, servers, or combinations thereof. The computer system1200ofFIG. 12includes one or more processor unit(s)1210and main memory1220. Main memory1220stores, in part, instructions and data for execution by processor unit(s)1210. Main memory1220stores the executable code when in operation, in this example. The computer system1200ofFIG. 12further includes a mass data storage1230, portable storage device1240, output devices1250, user input devices1260, a graphics display system1270, and peripheral devices1280.

The components shown inFIG. 12are depicted as being connected via a single bus1290. The components may be connected through one or more data transport means. Processor unit(s)1210and main memory1220is connected via a local microprocessor bus, and the mass data storage1230, peripheral devices1280, portable storage device1240, and graphics display system1270are connected via one or more input/output (I/O) buses.

Mass data storage1230, which can be implemented with a magnetic disk drive, solid state drive, or an optical disk drive, is a non-volatile storage device for storing data and instructions for use by processor unit(s)1210. Mass data storage1230stores the system software for implementing embodiments of the present disclosure for purposes of loading that software into main memory1220.

Portable storage device1240operates in conjunction with a portable non-volatile storage medium, such as a flash drive, floppy disk, compact disk, digital video disc, or Universal Serial Bus (USB) storage device, to input and output data and code to and from the computer system1200ofFIG. 12. The system software for implementing embodiments of the present disclosure is stored on such a portable medium and input to the computer system1200via the portable storage device1240.

User input devices1260can provide a portion of a user interface. User input devices1260may include one or more microphones, an alphanumeric keypad, such as a keyboard, for inputting alphanumeric and other information, or a pointing device, such as a mouse, a trackball, stylus, or cursor direction keys. User input devices1260can also include a touchscreen. Additionally, the computer system1200as shown inFIG. 12includes output devices1250. Suitable output devices1250include speakers, printers, network interfaces, and monitors.

Graphics display system1270include a liquid crystal display (LCD) or other suitable display device. Graphics display system1270is configurable to receive textual and graphical information and processes the information for output to the display device.

Peripheral devices1280may include any type of computer support device to add additional functionality to the computer system.

The components provided in the computer system1200ofFIG. 12are those typically found in computer systems that may be suitable for use with embodiments of the present disclosure and are intended to represent a broad category of such computer components that are well known in the art. Thus, the computer system1200ofFIG. 12can be a personal computer (PC), hand held computer system, telephone, mobile computer system, workstation, tablet, phablet, mobile phone, server, minicomputer, mainframe computer, wearable, or any other computer system. The computer may also include different bus configurations, networked platforms, multi-processor platforms, and the like. Various operating systems may be used including UNIX, LINUX, WINDOWS, MAC OS, PALM OS, QNX ANDROID, IOS, CHROME, TIZEN, and other suitable operating systems.

The processing for various embodiments may be implemented in software that is cloud-based. In some embodiments, the computer system1200is implemented as a cloud-based computing environment, such as a virtual machine operating within a computing cloud. In other embodiments, the computer system1200may itself include a cloud-based computing environment, where the functionalities of the computer system1200are executed in a distributed fashion. Thus, the computer system1200, when configured as a computing cloud, may include pluralities of computing devices in various forms, as will be described in greater detail below.

The present technology is described above with reference to example embodiments. Therefore, other variations upon the example embodiments are intended to be covered by the present disclosure.