CN101901601A - Method and system for reducing noise of voice communication in vehicle - Google Patents
Method and system for reducing noise of voice communication in vehicle Download PDFInfo
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Abstract
The invention discloses a method and a system for reducing noise of voice communication in a vehicle, relating to the field of voice noise reduction. The method comprises the following steps: shifting voice signal frequency spectrum to a high-frequency section in a transmitting end, carrying out separation of signal from noise in a receiving end, adopting adaptive-filtering to reduce the noise, and using frequency spectrum reduction to obtain a voice signal. The method is used to realize the purposes of achieving noise reduction and voice communication under the condition of having lower signal to noise ratio in the vehicle.
Description
Technical field
The present invention relates to the voice de-noising field, particularly a kind of method and system of reducing noise of voice communication in vehicle.
Background technology
Along with development of science and technology, the noise pollution in the modern transportation instrument passenger cabin becomes the topic that people pay close attention to.How in the environment of this relative closure, to reduce the noise pollution of being brought owing to engine running, air-flow and vehicle body friction and air-conditioning fan etc. as far as possible, thereby obtain the environment of gratifying rest and speech exchange, become the focus of domestic and international research.
The current demand that strengthens and discern at voice in the car handsfree communication facilities, the technology of the reduction internal car noise of employing is divided into traditional noise separation method and adaptive filter method.Wherein traditional noise isolation technics is to improve voice SNR (Signal to Noise Ratio in the car, signal to noise ratio (S/N ratio)) is target, noise detection technique based on small echo has successively been proposed, the noise isolation technics of subtracting each other based on noise spectrum and based on the relevant solutions such as noise reduction algorithm of microphone array.Wavelet technique is difficult to realize on the current number word signal processor owing to too complicated; The noise spectrum subtraction technique is owing to counting noise spectrum in advance, so will satisfy the constant ideal conditions of internal car noise frequency spectrum; The microphone array noise reduction is subject to number of microphone and array shape, is not suitable for the application of headphone.Application along with modern random digital signal theory, the particularly popularization of adaptive filter algorithm, adaptive active noise reduction earmuff has appearred, it gathers elementary neighbourhood noise by elementary microphone, the sef-adapting filter of sending in the controller produces secondary signal, through power amplification rear drive secondary sound source, produces the secondary signal identical with elementary acoustical signal frequency, that phase place is opposite, with the primary signal stack, realize the decay of noise.This method can reduce the low-frequency noise that common earmuff is difficult to decay, thereby on very wide frequency band, obtain comprehensive Noise Reduction effect preferably, as shown in Figure 1, wherein, H1 is the transition function of elementary sound source to the error microphone transmission path, and H2 is the transition function of elementary sound source to elementary microphone transmission path.
The inventor finds above-mentioned existing adaptive active noise reduction earmuff in realizing process of the present invention, just solved the problem of noise reduction, does not really solve the voice communication under noise background.In addition, from theoretical derivation and interpretation, the effect of above noise-reduction method all is to produce a relatively-stationary snr gain, but under the very low input signal-to-noise ratio situation of script, the effect of output with regard to still being difficult to reach satisfied.
Summary of the invention
In order to be implemented in the voice communication under the noise background, and in car than also well realizing noise reduction and voice communication under the situation of low signal-to-noise ratio, the invention provides a kind of method and system of reducing noise of voice communication in vehicle, said method comprising the steps of:
(1) transmitting terminal is the paramount frequency range of voice signal frequency spectrum shift, and the voice signal behind the frequency spectrum shift is sent in the air;
(2) voice signal and the ground unrest stack mixed signal that produced of receiving end after by the described frequency spectrum shift in the broadband microphone acquisition step (1);
(3) receiving end carries out low-pass filtering to the described mixed signal in the step (2), gets access to the low-frequency noise of separation and the voice signal behind the frequency spectrum shift respectively;
(4) receiving end is that described low-frequency noise in reference signal, the step (3) is that input signal carries out adaptive noise cancellation with the noise that directly imports people's ear in the air into;
(5) voice signal of receiving end after to the described frequency spectrum shift in the step (3) reduces processing, gets access to the clean speech signal, and described clean speech conversion of signals is become acoustical signal;
(6) receiving end superposes the residual signals of adaptive noise cancellation described in middle described acoustical signal that produces of step (5) and the step (4), and imports people's ear into.
Described receiving end is that described low-frequency noise in reference signal, the step (3) is that input signal carries out adaptive noise cancellation with the noise that directly imports people's ear in the air into, is specially:
As the reference signal, as input signal, adopt sef-adapting filter that the noise of the described people's of importing into ear is offset low-frequency noise with the noise that directly imports people's ear in the air into.
Described reduction in described adaptive noise cancellation in the step (4) and the step (5) is handled and is carried out simultaneously.
Described system comprises:
Dispensing device is used for the paramount frequency range of voice signal frequency spectrum shift, and the voice signal behind the frequency spectrum shift is sent in the air;
Receiving trap is used for gathering the mixed signal that voice signal behind the frequency spectrum shift of described dispensing device and ground unrest stack are produced by the broadband microphone; Described mixed signal is carried out low-pass filtering, get access to the low-frequency noise of separation and the voice signal behind the frequency spectrum shift respectively; With the noise that directly imports people's ear in the air into is that reference signal, described low-frequency noise are that input signal carries out adaptive noise cancellation; Voice signal behind the described frequency spectrum shift is reduced processing, get access to the clean speech signal, and described clean speech conversion of signals is become acoustical signal; With the residual signals stack of described acoustical signal and described adaptive noise cancellation, and import people's ear into.
Described receiving trap is that reference signal, described low-frequency noise are that input signal carries out adaptive noise cancellation with the noise that directly imports people's ear in the air into, is specially:
As the reference signal, as input signal, adopt sef-adapting filter that the noise of the described people's of importing into ear is offset low-frequency noise with the noise that directly imports people's ear in the air into.
Described adaptive noise cancellation in the described receiving trap and described reduction are handled and are carried out simultaneously.
The beneficial effect of the technical scheme that the embodiment of the invention provides is:
By at transmitting terminal with the voice signal frequency spectrum shift to high band, carrying out noise at receiving end separates, the employing auto adapted filtering carries out noise reduction and adopts the frequency spectrum reduction, obtain voice signal, realized in car than the purpose that also can well realize noise reduction and voice communication under the low signal-to-noise ratio situation by said method.
Description of drawings
Fig. 1 is the adaptive active noise cancelling headphone structured flowchart that provides in the prior art;
Fig. 2 is the method block diagram that the embodiment of the invention 1 provides;
Fig. 3 is the method flow diagram that the embodiment of the invention 1 provides;
Fig. 4 is a Volvo noise inside automobile frequency spectrum in the NOISEX-92 noise storehouse that provides of the embodiment of the invention 1;
Fig. 5 is the system schematic that the embodiment of the invention 2 provides;
Fig. 6 is the noise reduction that provides of the embodiment of the invention and the comparison diagram of microphone array noise reduction.
Embodiment
For making the purpose, technical solutions and advantages of the present invention clearer, embodiment of the present invention is described further in detail below in conjunction with accompanying drawing.
In order to be implemented in the voice communication under the noise background, and in car than also well realizing noise reduction and voice communication under the situation of low signal-to-noise ratio, the embodiment of the invention provides a kind of method of reducing noise of voice communication in vehicle, and referring to Fig. 2 and Fig. 3, this method thes contents are as follows:
By theoretical model research and actual measurement checking, internal car noise has following characteristics: the first, and the internal car noise frequency spectrum mainly concentrates on the following low-frequency range of 10kHz, as shown in Figure 4; The second, the environment inside car noise intensity is generally bigger, needs to consider that SNR hangs down the voice communication problem under the situation.
101: transmitting terminal is the paramount frequency range of voice signal frequency spectrum shift, and the voice signal behind the frequency spectrum shift is sent in the air;
Transmitting terminal is specially the method for the paramount frequency range of voice signal frequency spectrum shift: transmitting terminal with the voice signal frequency spectrum shift to supersonic range, for example: x (k) is a voice signal, fm is a centre frequency, xm (k) is the voice signal behind the frequency spectrum shift, then xm (k)=x (k) * cos (2 π * fm * k).
102: receiving end is gathered the mixed signal that voice signal behind the frequency spectrum shift and ground unrest stack are produced by the broadband microphone;
103: receiving end carries out low-pass filtering to the mixed signal that produces in the step 102, gets access to the low-frequency noise of separation and the voice signal behind the frequency spectrum shift respectively;
Because broadband Mike's wind action, and the imperfection of low-pass filter, make low-frequency noise n1 and ground unrest n coherent signal but also inequality each other.
Utilize internal car noise to concentrate on the characteristic of low-frequency range, for example: the low-frequency range that 10kHz is following, the voice signal frequency spectrum shift is arrived the very little high band of noise energy, obtain the voice signal behind the frequency spectrum shift, because internal car noise concentrates on low-frequency range, therefore receiving end can be easily with voice signal and noise separation, to reach the purpose of isolating speech signals and noise on frequency spectrum.
Wherein, the low-pass filter in this step can adopt common low-pass filter, and during specific implementation, the embodiment of the invention does not limit this.
104: receiving end is that reference signal, low-frequency noise are that input signal carries out adaptive noise cancellation with the noise that directly imports people's ear in the air into;
Particularly, with the noise n2 that directly imports people's ear in the air into (because people's ear is different with the position of broadband microphone, n2 and n each other coherent signal but and inequality) as with reference to signal, as input signal, adopt sef-adapting filter that the noise that imports people's ear into is offset low-frequency noise n1.Wherein, the sef-adapting filter in this step can be minimum mean square self-adaption filter, also can be the sef-adapting filter of other types, and during specific implementation, the embodiment of the invention does not limit this.
Wherein, in the process of adaptive noise cancellation, also can produce residual signals.
105: the voice signal after receiving end is moved step 103 intermediate frequency spectrum reduces processing, gets access to the clean speech signal, and the clean speech conversion of signals is become acoustical signal;
Voice signal behind the frequency spectrum shift reduced to handle be specially: it is poor that the low-frequency noise that gets access in mixed signal that produces in the step 102 and the step 103 is done, and multiply by with the carrier signal and the filtering of homophase frequently.
In order to improve the processing speed of system, guarantee real-time, preferably, adaptive noise cancellation in the step 104 and the reduction in the step 105 are handled and are carried out simultaneously.
106: receiving end is the residual signals stack of adaptive noise cancellation in the acoustical signal that produces in the step 105 and the step 104, and imports people's ear into.
In sum, the embodiment of the invention provides a kind of method of reducing noise of voice communication in vehicle, this method by at transmitting terminal with the voice signal frequency spectrum shift to high band, carrying out noise at receiving end separates, the employing auto adapted filtering carries out noise reduction and adopts the frequency spectrum reduction, obtain voice signal, realized the voice communication under noise background, and in car than also well realizing noise reduction and voice communication under the situation of low signal-to-noise ratio.
Embodiment 2
In order to be implemented in the voice communication under the noise background, and in car than also well realizing noise reduction and voice communication under the situation of low signal-to-noise ratio, the embodiment of the invention provides a kind of system of reducing noise of voice communication in vehicle, and referring to Fig. 5, this system for content is as follows:
Dispensing device is used for the paramount frequency range of voice signal frequency spectrum shift, and the voice signal behind the frequency spectrum shift is sent in the air;
Receiving trap is used for the mixed signal that is produced by voice signal behind the frequency spectrum shift of broadband microphone collection dispensing device and ground unrest stack; Mixed signal is carried out low-pass filtering, get access to the low-frequency noise of separation and the voice signal behind the frequency spectrum shift respectively; With the noise that directly imports people's ear in the air into is that reference signal, low-frequency noise are that input signal carries out adaptive noise cancellation; Voice signal behind the frequency spectrum shift is reduced processing, get access to the clean speech signal, and the clean speech conversion of signals is become acoustical signal; With the residual signals stack of acoustical signal and adaptive noise cancellation, and import people's ear into.
Further, receiving trap is that reference signal, low-frequency noise are that input signal carries out adaptive noise cancellation with the noise that directly imports people's ear in the air into, is specially:
As the reference signal, as input signal, adopt sef-adapting filter that the noise that imports people's ear into is offset low-frequency noise with the noise that directly imports people's ear in the air into.
Further, in order to improve the processing speed of system, guarantee real-time, preferably, adaptive noise cancellation in the receiving trap and reduction are handled and are carried out simultaneously.
In sum, the embodiment of the invention provides a kind of system of reducing noise of voice communication in vehicle, dispensing device by at transmitting terminal with the voice signal frequency spectrum shift to high band, receiving trap carries out noise to be separated, the employing auto adapted filtering carries out noise reduction and adopts the frequency spectrum reduction, obtain voice signal, realized the voice communication under noise background, and in car than also well realizing noise reduction and voice communication under the situation of low signal-to-noise ratio.
The embodiment of the invention is with 1 validity of simply verifying the method that the embodiment of the invention provides.
This experiment is based under the PC matlab6.5 environment, testing used tested speech signal x is monophony PCM file, sampling rate 96kHz, cutoff frequency is below 5kHz, noise n1 is that faithful record signal is a monophony PCM file under the interior idling mode of car, sampling rate 96kHz, and cutoff frequency is about 5kHz, frequency spectrum shift centre frequency fm is 35kHz, read voice and noise file, be adjusted into different input signal-to-noise ratios by convergent-divergent, low-pass filter adopts Butterworth 50 rank FIR wave digital lowpass filters, cutoff frequency is 0.25 π, the parameter of sef-adapting filter is: 10 rank, iterations n＜3000 o'clock, convergence coefficient u=0.002, n＞3000 o'clock, u=0.001.
Provided the synoptic diagram that the embodiment of the invention method that provides and the output signal-to-noise ratio that adopts the microphone array noise-reduction method to obtain are provided among Fig. 6, the output signal-to-noise ratio that curve 1 among Fig. 6 obtains for the method that adopts the embodiment of the invention to provide, the output signal-to-noise ratio of curve 2 for adopting the microphone array noise-reduction method to obtain, as can be seen from Figure 6, the method that adopts the embodiment of the invention to provide can get access to more stable signal to noise ratio (S/N ratio), especially when input signal-to-noise ratio is low, can get access to the output signal-to-noise ratio higher, satisfy the needs in the practical application than microphone array noise-reduction method.
By above-mentioned experimental verification, the feasibility of the method that provides of the embodiment of the invention can get access to more stable signal to noise ratio (S/N ratio) as can be seen, has satisfied the needs in the practical application.
It will be appreciated by those skilled in the art that accompanying drawing is the synoptic diagram of a preferred embodiment, the invention described above embodiment sequence number is not represented the quality of embodiment just to description.
The above only is preferred embodiment of the present invention, and is in order to restriction the present invention, within the spirit and principles in the present invention not all, any modification of being done, is equal to replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (6)
1. the method for a reducing noise of voice communication in vehicle is characterized in that, said method comprising the steps of:
(1) transmitting terminal is the paramount frequency range of voice signal frequency spectrum shift, and the voice signal behind the frequency spectrum shift is sent in the air;
(2) voice signal and the ground unrest stack mixed signal that produced of receiving end after by the described frequency spectrum shift in the broadband microphone acquisition step (1);
(3) receiving end carries out low-pass filtering to the described mixed signal in the step (2), gets access to the low-frequency noise of separation and the voice signal behind the frequency spectrum shift respectively;
(4) receiving end is that described low-frequency noise in reference signal, the step (3) is that input signal carries out adaptive noise cancellation with the noise that directly imports people's ear in the air into;
(5) voice signal of receiving end after to the described frequency spectrum shift in the step (3) reduces processing, gets access to the clean speech signal, and described clean speech conversion of signals is become acoustical signal;
(6) receiving end superposes the residual signals of adaptive noise cancellation described in middle described acoustical signal that produces of step (5) and the step (4), and imports people's ear into.
2. method according to claim 1 is characterized in that, described receiving end is that described low-frequency noise in reference signal, the step (3) is that input signal carries out adaptive noise cancellation with the noise that directly imports people's ear in the air into, is specially:
As the reference signal, as input signal, adopt sef-adapting filter that the noise of the described people's of importing into ear is offset low-frequency noise with the noise that directly imports people's ear in the air into.
3. method according to claim 1 is characterized in that, the described reduction in described adaptive noise cancellation in the step (4) and the step (5) is handled and carried out simultaneously.
4. the system of a reducing noise of voice communication in vehicle is characterized in that, described system comprises:
Dispensing device is used for the paramount frequency range of voice signal frequency spectrum shift, and the voice signal behind the frequency spectrum shift is sent in the air;
Receiving trap is used for gathering the mixed signal that voice signal behind the frequency spectrum shift of described dispensing device and ground unrest stack are produced by the broadband microphone; Described mixed signal is carried out low-pass filtering, get access to the low-frequency noise of separation and the voice signal behind the frequency spectrum shift respectively; With the noise that directly imports people's ear in the air into is that reference signal, described low-frequency noise are that input signal carries out adaptive noise cancellation; Voice signal behind the described frequency spectrum shift is reduced processing, get access to the clean speech signal, and described clean speech conversion of signals is become acoustical signal; With the residual signals stack of described acoustical signal and described adaptive noise cancellation, and import people's ear into.
5. system according to claim 4 is characterized in that, described receiving trap is that reference signal, described low-frequency noise are that input signal carries out adaptive noise cancellation with the noise that directly imports people's ear in the air into, is specially:
As the reference signal, as input signal, adopt sef-adapting filter that the noise of the described people's of importing into ear is offset low-frequency noise with the noise that directly imports people's ear in the air into.
6. system according to claim 4 is characterized in that, described adaptive noise cancellation in the described receiving trap and described reduction are handled and carried out simultaneously.
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