Patent Application
20150063583
The disclosures herein relate in general to audio signal processing, and in particular to a method and system for active noise cancellation.
A user may hear noise from a surrounding environment. A mechanical structure can attempt to physically buffer the user's ears against some of the noise, but the mechanical structure has limits. In addition to the mechanical structure, an active noise cancellation system can attempt to generate signals for cancelling at least some of the noise. Nevertheless, different techniques for active noise cancellation have respective shortcomings and trade-offs.
From at least a first microphone, first microphone signals are received that represent first sound waves. From at least a second microphone, second microphone signals are received that represent second sound waves. In response to the first microphone signals, first noise in the first sound waves is estimated, and first cancellation signals are output for causing a speaker array to generate first additional sound waves via at least a first acoustic beam for cancelling at least some of the first noise. In response to the second microphone signals, second noise in the second sound waves is estimated, and second cancellation signals are output for causing the speaker array to generate second additional sound waves via at least a second acoustic beam for cancelling at least some of the second noise.
The array 108 is suitable for acoustic beam forming. Examples of acoustic beam forming are described in co-owned U.S. Patent Application Publication No. 2012/0093348, co-owned U.S. Patent Application Publication No. 2012/0121113, and co-owned U.S. Pat. No. 8,396,233, which are hereby fully incorporated herein by reference. Accordingly, in response to signals from an active noise cancellation (“ANC”) unit 110, the array 108 generates: (a) at least a first acoustic beam through a region 112, so that at least first sound waves exist within an environment 114 (which is part of the region 112) around the ear 104; and (b) at least a second acoustic beam through a region 116, so that at least second sound waves (distinct from the first sound waves) exist within an environment 118 (which is part of the region 116) around the ear 106.
In the example of
Similarly, an error microphone 124 is located within the environment 118, and a reference microphone 126 is located outside the region 116. The error microphone 124: (a) converts, into signals, sound waves from the environment 118 (e.g., including sound waves of at least the second acoustic beam from the array 108); and (b) outputs those signals. The reference microphone 126: (a) converts, into signals, sound waves from outside the region 116 (e.g., ambient noise around the reference microphone 126); and (b) outputs those signals.
Accordingly, the signals from the error microphone 120 and the reference microphone 122 represent various sound waves (“first sounds”). The ANC unit 110: (a) receives and processes the signals from the error microphone 120 and the reference microphone 122; and (b) in response thereto, outputs signals for causing the array 108 to generate first additional sound waves (via at least the first acoustic beam) that cancel at least some noise in those first sounds.
Similarly, the signals from the error microphone 124 and the reference microphone 126 represent various sound waves (“second sounds”). The ANC unit 110: (a) receives and processes the signals from the error microphone 124 and the reference microphone 126; and (b) in response thereto, outputs signals for causing the array 108 to generate second additional sound waves (via at least the second acoustic beam) that cancel at least some noise in those second sounds.
In one example, the ANC unit 110 optionally: (a) receives audio signals from a left channel of an audio source 128 (“left audio”); and (b) combines the left audio into the first signals that the ANC unit 110 outputs to the array 108. Accordingly, in this example: (a) the array 108 generates the first additional sound waves to also represent the left audio's information (e.g., music and/or speech), which is audible to the ear 104 via at least the first acoustic beam; and (b) the ANC unit 110 suitably accounts for the left audio in its further processing (e.g., estimating noise) of the signals from the error microphone 120 for cancelling at least some noise in those sound waves.
Similarly, the ANC unit 110 optionally: (a) receives audio signals from a right channel of the audio source 128 (“right audio”); and (b) combines the right audio into the second signals that the ANC unit 110 outputs to the array 108. Accordingly, in this example: (a) the array 108 generates the second additional sound waves to also represent the right audio's information (e.g., music and/or speech), which is audible to the ear 106 via at least the second acoustic beam; and (b) the ANC unit 110 suitably accounts for the right audio in its further processing (e.g., estimating noise) of the signals from the error microphone 124 for cancelling at least some noise in those sound waves.
In one embodiment, a user interface 130 is a touchscreen, such as: (a) a liquid crystal display (“LCD”) device; and (b) touch-sensitive circuitry of such LCD device, so that the touch-sensitive circuitry is integral with such LCD device. In such embodiment, the user 102 operates the touchscreen (e.g., virtual keys thereof, such as a virtual keyboard and/or virtual keypad) for: (a) viewing information (e.g., alphanumeric text information) from the ANC unit 110; and (b) specifying information to the ANC unit 110, which receives that user-specified information from the touchscreen and operates in response thereto. Accordingly, the user 102 operates the user interface 130 to control various operations of the ANC unit 110.
Although
A mixer 304: (a) combines the first noise cancellation signals and the left audio (which the ANC unit 110 receives from the left channel of the audio source 128); and (b) outputs those combined signals to a spatial audio rendering unit 306. Similarly, a mixer 308: (a) combines the second noise cancellation signals and the right audio (which the ANC unit 110 receives from the right channel of the audio source 128); and (b) outputs those combined signals to the spatial audio rendering unit 306. In response to those signals from the mixers 304 and 308, the spatial audio rendering unit 306 causes the array 108 to generate the first and second acoustic beams through the regions 112 and 116, respectively.
For clarity, although
As discussed hereinabove in connection with
Although illustrative embodiments have been shown and described by way of example, a wide range of alternative embodiments is possible within the scope of the foregoing disclosure.
