Patent Application
20080304677
Undesirable sounds and noises from various sources such as snoring of a partner or humming of an air conditioner, etc. can be annoying at times when silence is desired, (such as during sleep, studying, etc.). Acoustic Echo Cancellation (AEC) is a technology that can mitigate such undesired sounds by a great magnitude. Products such as noise canceling headphones have been in the market for many years and the technology has even been used in fighter aircraft to mitigate the engine noise while the pilot is communication. Cell phones and many high-end speakerphones also use the AEC technology as well.
AEC techniques are very efficient in suppressing unwanted sounds usually targeted at a point, or rather a very small space around a listener's ears or a microphone. for instance, noise-canceling headphones that are worn on the head of a user. These headphones can easily cancel the unwanted sounds at the users' ears. In some instances the user may not like to use a headphone to achieve the benefits of AEC technology, either due to comfort or practicality, such as during sleep. This invention addresses the latter case.
In order to relieve a user from wearing a headphone or a similar device, a system and method for noise cancellation may be provided generally comprising, in one variation, a microphone for detecting sound, a processor for receiving the sound, generating a canceling waveform with respect to the detected sound, and transmitting the canceling waveform in the direction of a user's head via a speaker array. In one variation, the processor may contain a filtering subsystem, such as adaptive acoustic echo cancellation (AEC) subsystem. The AEC subsystem may separate desirable sounds from undesirable sounds, e.g., undesirable sounds which the user would find disruptive such as snoring, that are detected by the microphone. Speaker arrays can provide directionality to the sounds they produce, therefore noise canceling sounds may be localized by the speaker array (produced by the AEC block) around the user's head. This may be achieved by running localization algorithms to the sound signal provided to the speaker elements of the speaker array to achieve the maximum sound effect in a particular direction. The sound intensity can also be adjusted by a similar adaptive signal processing subsystem.
The system may contain one or more microphones which may be placed in close proximity to the user's head to provide an accurate sample of the sound amplitude perceived by the user. In one variation, at least one microphone may be used to detect a first desirable and undesirable sound and at least one other microphone in a different location may be used to detect a second version of the same desirable and undesirable sound. In another variation, the AEC subsystem may suppress the undesirable sound by generating a canceling waveform for transmission by the speaker array. The desirable sounds, such as alarms, sirens and cries, may be sampled by a processor and their signature stored in a memory unit. The AEC system may include a separate subsystem that checks for the signature of these types of sounds and if there is no match, allows the AEC subsystem to suppress it otherwise it will enhance it or at the very least not suppress it. In one variation, the AEC subsystem may enhance the desirable sound by generating an amplified waveform to the speaker array.
The speaker array may comprise of two or more speakers which have the capability to direct signals toward a given direction. In one variation, the speakers may be mounted on a controllably movable device, such as a gimbal, to allow the speakers to be adjusted such that they point toward the user's head. In the event the user moves his or her head out of range of the AEC speaker array performance, the system may further comprise an image tracking system which contains an image tracking device (e.g. a camera) which may be used to track the location of the user's head as he or she moves. When engaged, the image tracking system may actively track the user's head while transmitting the coordinates of the location of the user's head to a processor which may control the direction of the speaker array such that they actively point in the direction of the user's head. With the user's head location known and tracked, the canceling waveform may be transmitted to the head in the vicinity of the user's ears to thus actively cancel the undesired sounds prior to reaching the ears of the user. The cancelled undesirable sound results in silence or a mitigated amplitude perceived by the user regardless of the physical movement of the user.
Sound is transmitted as a pressure wave which consists of a compression phase and a decompression or rarefaction phase. When two sound waves pass through the same region of space at the same time, a phenomenon known as interference occurs. As shown in
As shown in
In another variation, a speaker array 16 in conjunction with a processor 22 containing a filtering feature such as acoustic echo cancellation (AEC) 24 may be utilized to eliminate or mitigate undesired sounds 10 received by the microphone 12. AEC algorithms are well utilized and are typically used to anticipate the signal which may re-enter the transmission path from the microphone 12 and cancel it out by digitally sampling an initial received signal to form a reference signal. Examples of acoustic echo cancellation are disclosed in U.S. Pat. Nos. 5,546,459; 5,661,813; and 7,003,099, the contents of which are incorporated herein by reference.
In the variation shown in
In the example shown in
The desired sound signals 26 may be transmitted via wired or wireless communication where the signal may be sampled and received by the AEC processor 22. A portion of the desired sound 26 may be transmitted to one or more speakers 16. The resulting echo from the speaker array 16, if any, may be detected by the second microphone 34 along with any other undesirable sound signals 10, as mentioned above. The undesired sound signals 10 detected by the second microphone 34 or the sampled signal received by AEC processor 22 may be processed and shifted out-of-phase, e.g., ideally 180° out-of-phase at each frequency, such that the summation of the two sound signals results in a cancellation of any echo and/or other undesired sounds 10.
The resulting summed sound signal may be redirected through an adaptive filter and re-summed to further clarify the sound signal until the desired sound signal is passed along to the speaker array 16 where the filtered sound signal 26, free or relatively free from the undesired sounds 10, may be transmitted to the user 20. Although two microphones 32, 34 are described in this example, an array of additional microphones may be utilized in close proximity to the user 20. Alternatively, one or more microphones may also be worn by the user 20, such as in an earring, necklace, etc. Furthermore, although two speakers 16 are illustrated, other variations may include more than two if so desired.
As the user 20 is likely to move his or her head 40 while asleep, the user 20 may potentially move out of the cone of performance of the speaker array 16 and thus reduce or lose the benefits that noise canceling provides. As a result, a noise canceling system 42 may also include an image tracking subsystem 44 with the capability to track the image of the head of the user 40 as he or she moves. As shown in
Similar to high-end speakerphone systems, each time the system (8, 30, 42) is installed or moved from its installed location to another location, a self localization procedure is performed in order for the whole system to determine its location with respect to the environment the system is operating in. This information together with the camera's motion tracking information provides the processor (14, 22, 48) with the exact information required for direction adjustments.
The applications of the systems and methods may be applied to other areas of noise cancellation. While illustrative examples are described above, it will be apparent to one skilled in the art that various changes and modifications may be made therein. Moreover, various systems or methods described above are also intended to be utilized in combination with one another, as practicable. The appended claims are intended to cover all such changes and modifications that fall within the true spirit and scope of the invention.
This application claims the benefit of priority to U.S. Provisional Patent Application Ser. No. 60/942,943 filed Jun. 8, 2007 which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60942943 | Jun 2007 | US |
