Patent Application
20110026733
This application claims foreign priority benefits under 35 U.S.C. §119 of Chinese Patent Application Serial No. 200910109073.3, filed on Jul. 29, 2009, the content of which is incorporated herein by reference in its entirety.
Exemplary embodiments of the present invention generally relate to an audio device, and in particular, relate to a device for cancelling background noise and method thereof.
In many communication systems, such as hands-free mobile phones, hearing aids, speech recognition systems, and voice control systems, it is critical to obtain desired speech signals from collected audio signals which may often be corrupted by a considerable amount of background noise signals. The high amount of background noise in a moving vehicle, for example, may render a speech communication system worthless.
Since background noise signals have similar characteristics as speech signals, many of the noise cancellation devices may discriminate speech signals from noise signals by comparing the collected signals with a predetermined noise threshold. Nevertheless, the noise may not be suppressed from the speech signals when the noise level suddenly increases or decreases. On the other side, the speech signals that are smaller than the predetermined noise threshold may possibly be lost.
According to one exemplary embodiment of the invention, a method for cancelling background noise of an audio device comprises determining characteristic values of an audio signal to construct a characteristic signal reflecting a change trend of the audio signal, multiplying the determined characteristic signal with the audio signal to construct a multiplication signal and amplifying the multiplication signal.
According to one exemplary embodiment of the invention, a device for cancelling background noise comprises a detecting unit configured to determine characteristic values of an audio signal to construct a characteristic signal reflecting a change trend of the audio signal. The device further comprises a multiplying unit configured to multiplying the characteristic signal with the audio signal to construct a multiplication signal and an amplifying unit configured to amplify the multiplication signal.
According to one exemplary embodiment of the invention, a method for cancelling background noise of an audio device comprises determining characteristic values of an audio signal to construct a characteristic signal reflecting a change trend of the audio signal, multiplying the determined characteristic signal with the audio signal to construct a multiplication signal and amplifying the multiplication signal. Steps of determining the characteristics of the audio signal, multiplying the determined characteristic signal with the audio signal to construct a multiplication signal and amplifying the multiplication signal are performed by one or more circuits configured to determine characteristic values of an audio signal to construct a characteristic signal reflecting a change trend of the audio signal, multiply the determined characteristic signal with the audio signal to construct a multiplication signal and amplify the multiplication signal.
The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawings. The embodiments illustrated in the figures of the accompanying drawings herein are by way of example and not by way of limitation. In the drawings:
The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. For example, a number of components or objects may be described herein in the singular, plural or as being “at least one” or “one or more.” It should be understood, however, that notwithstanding any particular quantity with which a component or object may be described herein, unless explicitly stated otherwise, the component or object may be in any of a number of different quantities, from the singular to the plural. Like numbers refer to like elements throughout.
To discriminate and cancel the noise signals from the speech signals, the received audio signals are passed to a detecting unit through the signal collecting unit, and are detected and processed at step S104. The received signals may comprise speech signals and noise signals. Characteristic values of the received audio signals may be determined as or after the detection and the processing to construct a characteristic signal reflecting a change trend of the audio signal. In one exemplary embodiment, the speech and noise signal may be associated with characteristics of which the speech signal typically exhibit large values, while the noise signal typically exhibit small values. For example, to make a phone call in an environment with a noise level of 85 db, the average characteristic value of speech signal is about 10˜30 mv, the average characteristic value of noise signal is below 5 mv.
At step S106, multiplications between the audio signals and the characteristic signals may be performed by a multiplying unit. After the multiplication, the product of the voice signal and its respective, associated characteristic signal is larger than that of the noise and its characteristic signal. In this regard, the discrimination level between the speech signals and the noise signals may be greatly increased. The results of the multiplication may be amplified by an amplifying unit at step S108.
In one exemplary embodiment, an additional step S110 may be performed after the audio signals have been received. At this step, the received audio signals may be pre-amplified before input to the detecting unit and the multiplying unit.
Additionally or alternatively, the values of the characteristics signals generated by the detecting unit may be input to a peak suppression unit, which may suppress at least a portion of the respective values at step S112. The peak suppressed characteristic signal may then be multiplied with their respective, associated audio signals at step S106.
Since the speech signal may correspond to large characteristic values and the noise signal may correspond to small characteristic values, the discrimination level between the speech signals and the noise signals may be greatly increased as a result of the multiplication. After the multiplying unit 204 performs the multiplication operation, the multiplying unit 204 may be configured to output the results of the multiplication operation to an amplifying unit 208 configured to further increase the discrimination level between the speech signals and the noise.
In operation, audio signals VS are collected from the microphone 420. Only AC signals in the vocal signals may pass through to the voltage follower circuit 422, while the DC bias may be blocked by the capacitor C1. Audio signals appear at the amplifier output 430, after the capacitor C1 and the operational amplifier U1.
In operation, the pre-amplifying unit 210 may be configured to detect a weak signal and strengthen it for further amplification. The pre-amplifying unit 210 may be configured to receive the audio signals AS from the signal collecting unit 202. The second operational amplifier circuit U2 may be configured to produce pre-amplified audio signal PAMP at the amplifier output 530. In various exemplary embodiments, the gain may be between four and five.
In operation, the FWR 632 is employed in detection of the audio signals. The audio signals may or may not be amplified before detection. As described above, the input of the FWR 632 may be the audio signals AS at the amplifier output 430 of the signal collecting unit 202 as shown in
In operation, when the positive input 736 (the characteristic signal CV) are at a higher voltage than the negative input 738 coupled to the pre-determined peak suppression voltage VF, the comparator U3 is configured to control the switch S1 switch to the negative input 738. On the other side, when the positive input 736 is at a lower voltage than the negative input 738, the comparator U3 is configured to control the switch S1 switch to the positive input 736. In this manner, the peak voltages may be suppressed. The peak suppressed characteristic signal may be accordingly referred to as peak suppressed characteristic signal PSCV.
In operation, the resistor R6 may be a variable resistor that may be configured to determine the input resistance of the operational amplifier U5. The output resistance may be determined by a mode control signal MC. When the switch S2 is closed in response to the mode control signal MC, the output resistance may be (R7+R8). Accordingly, the gain of the operational amplifier U5 may be (R7+R8)/R6. In another exemplary embodiment, the gain may be R7/R6 when the switch S2 is open. In other words, the gain of the operational amplifier U5 may be adjusted by the resistance of the variable resistor R6 and the mode control signal MC, according to various applications. By adjusting the gain of the operational amplifier U5, the noise signals may be strongly attenuated. The variable gain may also greatly amplify the speech signals.
It will be appreciated by those skilled in the art that changes could be made to the examples described above without departing from the broad inventive concept. It is understood, therefore, that this invention is not limited to the particular examples disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 200910109073.3 | Jul 2009 | CN | national |
