Patent Grant
9002036
This patent application is related to U.S. Pat. No. 8,130,979, issued Mar. 6, 2012, entitled, “NOISE MITIGATING MICROPHONE SYSTEM AND METHOD,” naming Kieran Harney, Jason Weigold, and Gary Elko as inventors, the disclosure of which is incorporated herein, in its entirety, by reference.
The invention generally relates to microphones and, more particularly, the invention relates to improving the performance of microphone systems.
Condenser microphones typically have a diaphragm that forms a capacitor with an underlying backplate. Receipt of an audible signal causes the diaphragm to vibrate to form a variable capacitance signal representing the audible signal. It is this variable capacitance signal that can be amplified, recorded, or otherwise transmitted to another electronic device.
Background noise often can degrade or otherwise swamp the input audible signal intended to be processed.
In accordance with one embodiment of the invention, a microphone system has a primary microphone for producing a primary signal, a secondary microphone for producing a secondary signal, and a selector operatively coupled with both the primary microphone and the secondary microphone. The system also has an output for delivering an output audible signal principally produced by one of the two microphones. The selector selectively permits 1) at least a portion of the primary signal and/or 2) at least a portion of the secondary signal to be forwarded to the output as a function of the noise in the primary signal.
It should be noted that respective portions of the primary signal or secondary signal may be processed prior to being forwarded to the output.
Moreover, the primary microphone may have a primary low frequency cut-off, while the secondary microphone may have a secondary low frequency cut-off that is greater than the primary low frequency cut-off. To that end, among other ways, the primary microphone may have a primary diaphragm and a primary circumferential gap defined at least in part by the primary diaphragm. In a similar manner, the secondary microphone may have a secondary diaphragm and a secondary circumferential gap defined at least in part by the secondary diaphragm. To provide the above noted low frequency cut-off relationship, the secondary circumferential gap may be greater than the primary circumferential gap.
In illustrative embodiments, the selector forwards at least a portion of the primary signal to the output if the noise is below about a predefined amount. In a corresponding manner, the selector may forward at least a portion of the secondary signal to the output if the noise is greater than about the predefined amount.
The portion of the primary signal illustratively is not forwarded to the output when the portion of the secondary signal is forwarded to the output. In like manner, the portion of the secondary signal illustratively is not forwarded to the output when the portion of the primary signal is forwarded to the output. Moreover, the selector may have a detector that detects saturation of the primary microphone.
In accordance with another embodiment of the invention, a microphone system has a primary microphone for producing a primary signal, a secondary microphone with a high pass filter for producing a secondary signal, and a base mechanically coupling the two microphones. The system also has a base mechanically coupling the primary and secondary microphones, a selector operatively coupled with the primary microphone and the secondary microphone, and an output. The selector, which has a detector for detecting low frequency noise, permits at least a portion of the primary signal to be forwarded to the output if the detector detects no low frequency noise. In a corresponding manner, the selector permits at least a portion of the secondary signal to be forwarded to the output if the detector detects low frequency noise.
Among other implementations, the primary and secondary microphones may be MEMS devices. In addition, among other things, the base may include a two way communication device (e.g., a mobile or cordless telephone).
Illustrative embodiments of the invention are implemented as a computer program product having a computer usable medium with computer readable program code thereon. The computer readable code may be read and utilized by a computer system in accordance with conventional processes.
The foregoing advantages of the invention will be appreciated more fully from the following further description thereof with reference to the accompanying drawings wherein:
In illustrative embodiments, a microphone system selects between the output of a primary and a secondary microphone based upon the noise level in the output of the primary microphone. More specifically, the secondary microphone is configured to not detect certain types of noise (e.g., low frequency noise, such as wind noise in a cellular telephone). As a result, its signal may not detect as wide a range of frequencies as those detected by the primary microphone.
In other words, the primary microphone may be more sensitive than the secondary microphone. As a result, the primary microphone may detect noise that is not detectable, or only partially detectable, by the secondary microphone. Accordingly, if the noise detected by the primary microphone exceeds some prespecified threshold, the microphone system delivers the output of the secondary microphone to its output. Although the output of the secondary microphone may not have as wide a frequency range, in many instances it still is anticipated to be more discernable than a signal from a primary microphone having significant noise. Details of illustrative embodiments are discussed below.
In alternative embodiments, the microphone system 12 is not fixedly secured to the telephone body 14—it may be movably secured to the telephone body 14. Since they are mechanically coupled, both microphones 18A and 18B nevertheless still should receive substantially the same mechanical signals as discussed above. For example, the two microphones 18A and 18B may be formed on a single die that is movably connected to the telephone body 14. Alternatively, the microphones 18A and 18B may be formed by separate dies packaged together or separately.
The base 10 may be any structure that can be adapted to use a microphone. Those skilled in the art thus should understand that other structures may be used as a base 10, and that the mobile telephone 10 is discussed for illustrative purposes only. For example, among other things, the base 10 may be a movable or relatively small device, such as the dashboard of an automobile, a computer monitor, a video recorder, a camcorder, or a tape recorder. The base 10 also may be a surface, such as the substrate of a single chip or die, or the die attach pad of a package. Conversely, the base 10 also may be a large or relatively unmovable structure, such as a building (e.g., next to the doorbell of a house).
The selector 19 also may have some multiplexing apparatus (i.e., a multiplexer 23) that forwards one of the two noted microphone signals to its output. To that end, the microphone may have a select input for receiving a select signal from a detector 21. If the select signal is a first value (e.g., logical “1”), the multiplexer 23 will forward the output signal of the primary microphone 18A. To the contrary, if the selector 19 is a second value (e.g., logical “0”), then the multiplexer 23 will forward the output of the secondary microphone 18B.
Of course, it should be noted that discussion of the specific means for performing the selection is illustrative and not intended to limit various embodiments. Those skilled in the art should understand that other implementations may be used.
The detector 21 forwards, as a function of the noise levels of the output signal of the primary microphone 18A, a first amplification value X to the first amplifier A1, and a second amplification value 1-X to the second amplifier A2. These amplification values determine the relative compositions of the signals of the two amplifiers A1 and A2 within the final selector signal. A summing module 36 thus sums the outputs of these two amplifiers A1 and A2 to produce the final output signal of the selector 19.
For example, if there the output of the primary microphone 18A has no noise, the detector 21 may set the value “X” to “1.” As a result, the signal from the primary microphone 18A is fully passed to the summing module 36, while no portion of the signal of the secondary microphone 18B is passed. When the noise is at some intermediate level, however, portions of both signals from the two microphones 18A and 18B may form the final selector output signal. In other words, in this case, the selector output signal is a combination of the signals from both microphones 18A and 18B. Of course, when it detects a significant enough noise level in the primary microphone output signal, the detector 21 may set the value “X” to “0,” which causes no part of the primary microphone signal to reach the output. Instead, in that case, the output signal of the secondary microphone 18B forms the final output signal of the selector 19.
The detector 21 may determine an appropriate value for “X” by any number of means. For example, the detector 21 generate the value “X” by using a look-up table in internal memory, or an internal circuit that generates the value on the fly.
Various embodiments may use any conventional microphone in the art that can be adapted for the discussed purposes.
Audio signals cause the diaphragm 24 to vibrate, thus producing a changing capacitance. On-chip or off-chip circuitry (not shown) converts this changing capacitance into electrical signals that can be further processed. It should be noted that discussion of the microphone of
As noted above, the two microphones illustratively are configured to have different sensitivities (i.e., to be responsive to signals having different frequency ranges). Among other ways, those two frequency ranges may overlap at higher frequencies. For example, the primary microphone 18A may be responsive to signals from a very low-frequency (e.g., 100 hertz) up to some higher frequency. The secondary microphone 18B, however, may be responsive to signals from a higher low frequency (e.g., 500 Hertz) up to the same (or different) higher frequency as the primary microphone 18A. Of course, it should be noted that these discussed frequency ranges are illustrative and not intended to limit various aspects of the invention.
To those ends,
As known by those skilled in the art, it is generally desirable to minimize the size of that gap (e.g., gap 1) to ensure that the microphone can respond to low-frequency audio signals. In other words, if the gap is too large, the microphone may not be capable of detecting audio signals having relatively low frequencies. Specifically, with respect to the frequency response of a microphone, the location of its low frequency cut-off (e.g., the 30 dB point) is a function of this gap.
In accordance with one embodiment of the invention, gap 2 (of the secondary microphone 18B) is larger than gap 1 (of the primary microphone 18A). Accordingly, as shown in
There are various ways to make gap 2 larger than gap 1 while still ensuring that both microphones 18A and 18B have substantially identical responses to noise signals. Among other ways, the diaphragms 24 may be formed to have substantially identical masses. To that end, the diaphragm 24 of the secondary microphone 18B may be thicker than the diaphragm 24 of the primary microphone 18A, while the diameter of the diaphragm 24 of the secondary microphone 18B is smaller than the diameter of the diaphragm 24 of the primary microphone 18A.
In general terms, the embodiments shown in
The entire microphone system 12 may be formed in a number of different manners. For example, the system 12 could be formed within a single package as separate dies (e.g., the microphone 18A, microphone 18B, and selector 19 as separate dies), or on the same dies. As another example, the system 12 could be formed from separately packaged elements that cooperate to produce the desired output.
During operation, both microphones should receive substantially the same audio signal (e.g., a person's voice) and associated noise. For example, noise can include, among other things, wind blowing into the microphones, the impact of the telephone being dropped on the ground, rubbing of a phone against a user's face, or noise in a camera from a motor moving a lens. The secondary microphone 18B should not detect this noise if the frequency of the noise signal is below its low frequency cut-off F2. To the contrary, however, the primary microphone 18A detects this noise. The selector 19 therefore determines if this noise is of such a magnitude that the output signal from the secondary microphone 18B should be used. For example, if the noise saturates the primary microphone circuitry, then the selector 19 may forward the output signal from the secondary microphone 18B to the output.
Those skilled in the art understand that when there is no noise, the quality of the signal produced by the secondary microphone 18B may not be as good as that of the primary microphone 18A. Noise nevertheless may change that, thus causing the quality of the signal from the secondary microphone 18B to be better than that of the signal from the primary microphone 18A. Accordingly, despite its nominally less optimal performance, the output signal of the secondary microphone 18B may be more desirable than that of the primary microphone 18A.
In alternative embodiments, rather than using the logical high pass filter (e.g., the larger gap), the secondary microphone 18B has an actual high pass filter. To that end, both microphones 18A and 18B may be substantially structurally the same and thus, have substantially the same responses to audio signals. The output of the secondary microphone 18B, however, may be directed to a high pass filter, which filters out the low frequency signals (e.g., the noise). Accordingly, if the selector 19 detects low frequency noise, such as wind, it may direct the output of the high pass filter to the output of the microphone system 12. This should effectively produce a similar result to that of other embodiments discussed above.
Various embodiments of the invention may be implemented at least in part in any conventional computer programming language. For example, some embodiments may be implemented in a procedural programming language (e.g., “C”), or in an object oriented programming language (e.g., “C++”). Other embodiments of the invention may be implemented as preprogrammed hardware elements (e.g., the selector 19 may be formed from application specific integrated circuits, FPGAs, and/or digital signal processors), or other related components.
In an alternative embodiment, the disclosed apparatus and methods (e.g., see the flow chart described above) may be implemented as a computer program product for use with a computer system. Such implementation may include a series of computer instructions fixed either on a tangible medium, such as a computer readable medium (e.g., a diskette, CD-ROM, ROM, or fixed disk) or transmittable to a computer system, via a modem or other interface device, such as a communications adapter connected to a network over a medium. The medium may be either a tangible medium (e.g., optical or analog communications lines) or a medium implemented with wireless techniques (e.g., WIFI, microwave, infrared or other transmission techniques). The series of computer instructions can embody all or part of the functionality previously described herein with respect to the system.
Those skilled in the art should appreciate that such computer instructions can be written in a number of programming languages for use with many computer architectures or operating systems. Furthermore, such instructions may be stored in any memory device, such as semiconductor, magnetic, optical or other memory devices, and may be transmitted using any communications technology, such as optical, infrared, microwave, or other transmission technologies.
Among other ways, such a computer program product may be distributed as a removable medium with accompanying printed or electronic documentation (e.g., shrink wrapped software), preloaded with a computer system (e.g., on system ROM or fixed disk), or distributed from a server or electronic bulletin board over the network (e.g., the Internet or World Wide Web). Of course, some embodiments of the invention may be implemented as a combination of both software (e.g., a computer program product) and hardware. Still other embodiments of the invention are implemented as entirely hardware, or entirely software.
Although the above discussion discloses various exemplary embodiments of the invention, it should be apparent that those skilled in the art can make various modifications that will achieve some of the advantages of the invention without departing from the true scope of the invention.
This patent application is a continuation patent application of U.S. patent application Ser. No. 11/828,049, filed on Jul. 25, 2007, entitled, “MULTIPLE MICROPHONE SYSTEM,” naming Kieran Harney, Jason Weigold, and Gary Elko as inventors, which claims priority from provisional U.S. patent application No. 60/833,032, filed Jul. 25, 2006, entitled, “MULTIPLE MICROPHONE SYSTEM,” naming Kieran Harney, Jason Weigold, and Gary Elko as inventors. The disclosures of both patent applications are incorporated herein, in their entireties, by reference.
| Number | Name | Date | Kind |
|---|---|---|---|
| 5226087 | Ono et al. | Jul 1993 | A |
| 6101258 | Killion et al. | Aug 2000 | A |
| 7181030 | Rasmussen et al. | Feb 2007 | B2 |
| 20020009203 | Erten | Jan 2002 | A1 |
| 20020057815 | Killion | May 2002 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20120207324 A1 | Aug 2012 | US |
| Number | Date | Country | |
|---|---|---|---|
| 60833032 | Jul 2006 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11828049 | Jul 2007 | US |
| Child | 13454508 | US |
