Patent Application
20100123785
1. Field
Embodiments of the invention relate to the field of audio beamforming; and more specifically, to the aiming of audio beamforming.
2. Background
Under typical imperfect conditions, a single microphone that is embedded in a mobile device does a poor job of capturing sound because of background sounds that are captured along with the sound of interest. An array of microphones can do a better job of isolating a sound source and rejecting ambient noise and reverberation.
Beamforming is a way of combining sounds from two or more microphones that allows preferential capture of sounds coming from certain directions. In a delay-and-sum beamformer sounds from each microphone are delayed relative to sounds from the other microphones, and the delayed signals are added. The amount of delay determines the beam angle—the angle in which the array preferentially “listens.” When a sound arrives from this angle, the sound signals from the multiple phones are added constructively. The resulting sum is stronger, and the sound is received relatively well. When a sound arrives from another angle, the delayed signals from the various microphones add destructively—with positive and negative parts of the sound waves canceling out to some degree—and the sum is not as loud as an equivalent sound arriving from the beam angle.
For example, if the sound comes into the microphone on the right before it enters the microphone on the left, then you know the sound source is to the right of the microphone array. During sound capturing, the microphone array processor can aim a capturing beam in the direction of the sound source. Beamforming allows a microphone array to simulate a highly directional microphone pointing toward the sound source. The directivity of the microphone array reduces the amount of captured ambient noises and reverberated sound as compared to a single microphone. This may provide a clearer representation of a speaker's voice.
A beamforming microphone array may made up of distributed omnidirectional microphones linked to a processor that combines the several inputs into an output with a coherent form. Arrays may be formed using numbers of closely spaced microphones. Given a fixed physical relationship in space between the different individual microphone transducer array elements, simultaneous digital signal processor (DSP) processing of the signals from each of the individual microphones in the array can create one or more “virtual” microphones. Different algorithms permit the creation of virtual microphones with extremely complex virtual polar patterns and even the possibility to steer the individual lobes of the virtual microphones patterns so as to home-in-on, or to reject, particular sources of sound. Beamforming techniques, however, rely on knowledge of the location of the sound source. Therefore it is necessary to aim the beamforming at the intended sound source to benefit from the use of a microphone array.
A device to provide an audio output includes a microphone array, a signal processor, and a graphic user interface (GUI). The signal processor is coupled to the microphone array to perform audio beamforming with input from the microphone array. The GUI is coupled to the signal processor to display a plurality of audio sources, to receive a selection of at least one of the plurality of audio sources from a user, and to provide the selection to the signal processor for aiming the audio beamforming toward the selected audio source. The selection may be made by touching the display. The device may further include a camera and the GUI may display an image received from the camera as the plurality of audio sources. The camera may provide a moving video image and the signal processor may provide a synchronized audio signal aimed at the selected audio source.
Other features and advantages of the present invention will be apparent from the accompanying drawings and from the detailed description that follows below.
The invention may best be understood by referring to the following description and accompanying drawings that are used to illustrate embodiments of the invention by way of example and not limitation. In the drawings, in which like reference numerals indicate similar elements:
In the following description, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known circuits, structures and techniques have not been shown in detail in order not to obscure the understanding of this description.
A signal processor 24 is coupled to the microphone array to produce the audio output using audio beamforming with input from the microphone array.
The signal processor 24 may identify a spatial arrangement of sounds received by the microphone array 12, 14 and provides the spatial arrangement to the GUI 20. The GUI may display a graphic representation of the spatial arrangement of audio sources as the image of the plurality of audio sources. The spatial arrangement identified by the signal processor 24 may be in the form of a plurality of beamforming angles that are directed to the plurality of audio sources. The spatial arrangement may identify only one dimension. Therefore, the graphic representation of the spatial arrangement of audio sources may be a somewhat abstract representation.
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The signal processor 24 may identify a spatial arrangement of sounds received by the microphone array 12, 14 and provide the spatial arrangement to the GUI 20. As shown in
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The image processor 22 may receive the spatial arrangement of sounds received by the microphone array 12, 14 identified by the signal processor 24. As shown in
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It will be appreciated that the selection on the GUI 20 may provide a width and a height of the audio source at which the beamforming is to be aimed but the beamforming may be responsive to one dimension of the selection such as the width.
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The device may be a camera that provides a moving video image with the signal processor providing a synchronized audio signal aimed at the selected audio source as the audio output. In other embodiments, the camera, if present, may be used only to provide images to the image processor to assist in the aiming of the audio beamforming with the device providing only an audio output aimed at the selected audio source.
While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that this invention is not limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those of ordinary skill in the art. The description is thus to be regarded as illustrative instead of limiting.
