WO2007122923A1 - 雑音抑圧装置 - Google Patents
雑音抑圧装置 Download PDFInfo
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- WO2007122923A1 WO2007122923A1 PCT/JP2007/055266 JP2007055266W WO2007122923A1 WO 2007122923 A1 WO2007122923 A1 WO 2007122923A1 JP 2007055266 W JP2007055266 W JP 2007055266W WO 2007122923 A1 WO2007122923 A1 WO 2007122923A1
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- 238000001514 detection method Methods 0.000 claims abstract description 140
- 230000005236 sound signal Effects 0.000 claims abstract description 106
- 239000002131 composite material Substances 0.000 claims abstract description 96
- 230000005684 electric field Effects 0.000 claims abstract description 83
- 230000001629 suppression Effects 0.000 claims description 61
- 230000000630 rising effect Effects 0.000 claims description 37
- 238000001228 spectrum Methods 0.000 claims description 27
- 238000000034 method Methods 0.000 claims description 12
- 230000001131 transforming effect Effects 0.000 claims 2
- 230000001360 synchronised effect Effects 0.000 abstract description 4
- 238000010586 diagram Methods 0.000 description 21
- 238000012545 processing Methods 0.000 description 21
- 230000006870 function Effects 0.000 description 17
- 238000005516 engineering process Methods 0.000 description 8
- 238000012986 modification Methods 0.000 description 8
- 230000004048 modification Effects 0.000 description 8
- 230000000694 effects Effects 0.000 description 7
- 230000007423 decrease Effects 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 4
- 230000007257 malfunction Effects 0.000 description 4
- 238000005070 sampling Methods 0.000 description 4
- 230000001934 delay Effects 0.000 description 3
- 239000000284 extract Substances 0.000 description 3
- 230000010354 integration Effects 0.000 description 3
- 230000003595 spectral effect Effects 0.000 description 3
- 241000234671 Ananas Species 0.000 description 1
- 238000012935 Averaging Methods 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 238000003708 edge detection Methods 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/06—Receivers
- H04B1/10—Means associated with receiver for limiting or suppressing noise or interference
- H04B1/1027—Means associated with receiver for limiting or suppressing noise or interference assessing signal quality or detecting noise/interference for the received signal
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03G—CONTROL OF AMPLIFICATION
- H03G3/00—Gain control in amplifiers or frequency changers
- H03G3/20—Automatic control
- H03G3/30—Automatic control in amplifiers having semiconductor devices
- H03G3/34—Muting amplifier when no signal is present or when only weak signals are present, or caused by the presence of noise signals, e.g. squelch systems
- H03G3/345—Muting during a short period of time when noise pulses are detected, i.e. blanking
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04H—BROADCAST COMMUNICATION
- H04H40/00—Arrangements specially adapted for receiving broadcast information
- H04H40/18—Arrangements characterised by circuits or components specially adapted for receiving
- H04H40/27—Arrangements characterised by circuits or components specially adapted for receiving specially adapted for broadcast systems covered by groups H04H20/53 - H04H20/95
- H04H40/36—Arrangements characterised by circuits or components specially adapted for receiving specially adapted for broadcast systems covered by groups H04H20/53 - H04H20/95 specially adapted for stereophonic broadcast receiving
- H04H40/45—Arrangements characterised by circuits or components specially adapted for receiving specially adapted for broadcast systems covered by groups H04H20/53 - H04H20/95 specially adapted for stereophonic broadcast receiving for FM stereophonic broadcast systems receiving
- H04H40/72—Arrangements characterised by circuits or components specially adapted for receiving specially adapted for broadcast systems covered by groups H04H20/53 - H04H20/95 specially adapted for stereophonic broadcast receiving for FM stereophonic broadcast systems receiving for noise suppression
Definitions
- the present invention relates to a noise suppression device and a noise cancellation technique for performing noise suppression and noise cancellation of an FM (frequency modulation) radio receiver with low electric field strength.
- FM radio receivers take measures against various types of noise to improve sound quality.
- in-vehicle radio receivers for example, pulse noise caused by engine rotation, wipers, electric mirrors, etc. may be a problem, and noise cancellation technology has been proposed and used to eliminate this! /
- FIG. 1 is a block diagram showing the configuration of a conventional pulse noise canceller.
- Figure 2 (a) shows the relationship between the HPF (high pass filter) output and the AGC output when pulse noise occurs.
- Figure 2 (b) shows the relationship between HPF output and AGC output when the electric field drops.
- Figure 2 (c) shows the relationship between the HPF output and the AGC output when the electric field drops and pulse noise occurs.
- a conventional pulse noise canceller includes a delay device 100, a pulse detection unit 200, and a pulse suppression unit 300.
- the FM composite signal is input to the pulse detector 200, and pulse noise is detected.
- the pulse suppression unit 300 removes the pulse noise in the detection section.
- the pulse detector 200 includes a high-pass filter (HPF) 201, an AGC circuit 202, and a comparator 203.
- the high-pass filter 201 passes only the high-frequency component of the FM composite signal.
- the AGC circuit 202 applies gain control according to the output signal level of the high pass filter 201. Ingredients Specifically, as shown in Fig.
- the pulse detection unit 200 compares the output level of the AGC circuit 202 with a predetermined threshold (the “second threshold” in the claims), detects when the AGC output level exceeds the threshold, as pulse noise, Controls the suppression unit 300.
- a predetermined threshold the “second threshold” in the claims
- the pulse suppression unit 300 can be realized by an interpolation circuit that outputs an input signal as it is during a pulse non-detection period and holds, for example, a value immediately before the detection period in a pulse detection period.
- Patent Document 1 Japanese Patent No. 3213495
- pulse noise is generated in addition to white background noise.
- the amplitude of the signal can be increased by inserting an IF amplifier and the received electric field strength can be increased, so pulse noise in a weak electric field was not a problem.
- digital radio receivers can perform processing corresponding to the electric field strength on a sample-by-sample basis rather than performing amplitude control based on the long-term average of the input signal. Don't implement! For this reason, the influence of such pulse noise appears remarkably, and there is a problem that it must be removed.
- FIG. 3 (a) is a diagram illustrating the frequency characteristics of the FM composite signal, the low-pass filter output, and the pulse noise during a strong electric field.
- Figure 3 (b) shows the frequency characteristics of the FM composite signal, mouth-pass filter, pulse noise, and background noise in a weak electric field.
- the FM composite signal includes a (L + R) signal 901 for monaural broadcasting and an (LR) signal 902 for stereo broadcasting.
- the received FM signal is a monophonic power stereo broadcast or not is determined by whether or not a 19 kHz pilot signal 905 is present.
- the pulse noise 903 included in the received FM signal includes components in the entire frequency band, the pulse noise 903 is detected by extracting a component in the higher frequency range than the composite signal band with a high-pass filter. I was able to.
- the background noise 906 increases as shown in FIG. As a feature of FM broadcasting, this background noise 906 becomes larger as it goes higher, so it becomes difficult to accurately detect the pulse noise 903 even if a higher frequency component is extracted from the composite signal.
- a mono audio signal that is, (L + R) signal 901
- the frequency characteristic 904 of the low-pass filter allows the (L + R) signal 901 in the band of approximately 15 kHz or less to pass through the band of approximately 20 kHz or less in order to extract the FM composite signal force. Therefore, as shown in Fig. 3 (a), in a strong electric field, the pulse noise is higher than the (L + R) signal 901 and passes through the low-pass filter, that is, between 15 kHz and 20 kHz. 903 should be detected.
- the present invention solves such a problem, and aims to eliminate weak electric field pulse noise generated by a decrease in received electric field, and provides a noise suppression device capable of obtaining a great sound quality improvement effect without malfunction.
- the purpose is to provide.
- a noise suppression device of the present invention is a noise suppression device that suppresses pulse noise at a low electric field strength included in a frequency-modulated signal, and demodulates an FM baseband signal.
- Band limiting means for outputting an audio signal by band limiting the composite signal obtained to a frequency equal to or lower than a predetermined frequency, and pulse detection for detecting pulse noise in the audio signal output by the band limiting means And when the pulse signal is included at a position corresponding to the pulse noise detected in the audio signal in the high frequency component of the composite signal.
- the pulse detection means for determining that the detection result is valid, and the pulse detection means by the pulse determination means If the detection result is determined to be valid, characterized in that it comprises a pulse suppression means for suppressing the detected pulse noise in the audio signal.
- the present invention can be realized as a method in which processing means constituting the device can be realized as a step, or can be realized as a program for causing a computer to execute the step, or the program can be recorded. It can be realized as a computer-readable recording medium such as a CD ROM, or as information, data or a signal indicating the program. These programs, information, data, and signals may be distributed via communication networks such as the Internet! /.
- the amplitude value of the composite signal sample synchronized with the weak electric field pulse noise detection interval in the audio signal is compared with the predetermined threshold, and the amplitude of the composite signal in the detection interval is determined.
- the threshold value is exceeded, it is determined that the noise is pulse noise, so that the pulse noise in the audio signal is discriminated from the high frequency component of the signal.
- the noise subtractor in the frequency domain is removed. Do Chillon. Thereby, it is possible to suppress an increase in the level of the frequency spectrum of the audio signal including pulse noise due to the spectrum of pulse noise. As a result, the frequency spectrum power of the audio signal also has the effect of removing the noise pattern corresponding to the electric field strength and making it possible to reproduce an audio signal closer to the original sound.
- FIG. 1 is a block diagram showing the configuration of a conventional noise noise canceller.
- Fig. 2 shows the relationship between the HPF output and the AGC output when pulse noise occurs.
- Figure 2 (b) shows the relationship between the HPF output and the AGC output when the electric field drops.
- Figure 2 (c) shows the relationship between the HPF output and the AGC output when the electric field is reduced and noise noise is generated.
- Fig. 3 shows the frequency characteristics of the FM composite signal, low-pass filter output, and pulse noise in a strong electric field.
- Figure 3 (b) shows the frequency characteristics of the FM composite signal, low-pass filter, pulse noise, and background noise in a weak electric field.
- FIG. 4 is a block diagram showing a configuration of an FM radio receiver using the noise suppression device of the present invention.
- FIG. 5 (a) is a diagram showing an example of a waveform of a composite signal including pulse noise.
- Figure 5 (b) shows an example (sine wave) of an audio signal waveform containing pulse noise.
- FIG. 6 is a block diagram showing a configuration of an FM radio receiver including a modulation rate detection unit.
- FIG. 7 is a block diagram showing a configuration of an FM radio receiver having a composite processing unit.
- FIG. 8 is a block diagram showing a configuration of an FM radio receiver using the weak electric field pulse noise canceller of Embodiment 2 of the present invention.
- FIG. 9 is a block diagram showing a configuration of an FM radio receiver that is a first modification of the second embodiment.
- FIG. 10 is a block diagram showing a configuration of the FM radio receiver of the third embodiment in which a weak electric field noise canceling unit is provided after the noise suppressing unit shown in FIG.
- FIG. 11 is a block diagram showing an internal configuration of the weak electric field noise cancellation unit shown in FIG.
- FIG. 4 is a block diagram showing a configuration of an FM radio receiver using the noise suppression device of the present invention.
- the FM radio receiver shown in Fig. 4 extracts a low-frequency monaural audio signal from the composite signal, detects pulse noise contained in the extracted monaural audio signal, and detects the detected pulse.
- the FM radio receiver includes the noise suppression device (band limiting unit and noise suppression unit) of the present invention that suppresses the pulse noise.
- Antenna 1 front end 2, IF processing unit 3, FM demodulation unit 4, band limiting unit 5 and noise suppression unit 6 are provided.
- antenna 1 receives the radio signal.
- Front end 2 converts the received radio signal to an intermediate frequency (IF) signal.
- the IF processing unit 3 converts the IF signal into a baseband (BB) signal.
- the FM demodulator 4 demodulates the BB signal into a composite signal.
- the band limiting unit 5 extracts the (L + R) signal and the (L ⁇ R) signal as well as the composite signal power including the high frequency, mixes them, and stereo audio signal of L and R Is output.
- the electric field strength is low, only the demodulated composite signal power is extracted only in the low range, for example, the band of 20 kHz or less, and the monaural audio signal represented by the (L + R) signal is output.
- the noise suppression unit 6 passes through the stereo audio signal output from the band limiting unit 5 without doing anything.
- the band limiting unit 5 and the noise suppressing unit 6 have a function of “a noise suppressing device that suppresses pulse noise at a low electric field strength included in a frequency-modulated signal”.
- the composite signal obtained by demodulating the baseband signal is band-limited to a band below the specified frequency to limit the audio signal.
- the function of “band limiting means for output” is provided.
- various noise quality improvement technologies such as separation control and noise cut have been proposed for noise suppression processing, as well as noise noise cancellation! /
- weak electric field pulse noise cancellation is proposed! /, Only explained.
- the noise suppression unit 6, which is a weak electric field pulse noise canceller, includes a delay unit 61, a pulse detection unit 62, a pulse determination unit 63, a pulse suppression unit 64, a delay unit 65, and a comparator 66.
- the delay device 61 delays the monaural audio signal output from the band limiting unit 5 by the processing time of the pulse detection unit 62.
- the pulse detection unit 62 has a function of “pulse detection means for detecting pulse noise in the audio signal output by the band limiting unit”, and receives the monaural audio signal output from the band limiting unit 5 as an input. Detecting a pulse candidate and outputting a pulse detection signal.
- the pulse detector 62 has the same configuration as that of the conventional pulse detection method using the high-pass filter shown in FIG.
- the pulse detection unit 62 has the same configuration as the pulse detection unit 200 shown in FIG. 1, detects pulse noise in the input audio signal, and outputs a pulse detection signal.
- the pulse detection signal is a specific signal as long as it represents a state in which pulse noise is detected and a state in which pulse noise is not detected. Does not matter.
- the pulse determination unit 63 determines whether or not the audio signal in the pulse detection period is pulse noise. If the audio signal in the pulse detection period is pulse noise, the pulse determination unit 63 passes through the delay unit 61 corresponding to the detection delay.
- the pulse suppressor 64 removes the noise noise from the input audio signal.
- the method for determining whether or not the audio signal in the pulse detection section is pulse noise is as follows.
- FIG. 5 (a) is a diagram illustrating an example of a waveform of a composite signal including pulse noise.
- Figure 5 (b) is a diagram showing an example (sine wave) of an audio signal waveform that includes pulse noise.
- the composite signal when the field strength is low, the composite signal contains many high-frequency components.
- the audio signal is a low-frequency signal except for the pulse noise.
- the “S” line sound, etc. contains a high-frequency component, unlike the waveform shown in Fig. 5 (b). It is not detected as pulse noise. May be.
- the pulse determination unit 63 determines whether or not the audio signal in the pulse detection section is pulse noise as follows. In other words, the pulse determination unit 63 compares the composite signal synchronized with the pulse detection signal by the delay unit 65 with a predetermined threshold value (“first threshold value” in the claims) by the comparator 66, When the amplitude of the composite signal exceeds the threshold during the detection interval, it is judged as pulse noise.
- the pulse determination unit 63 detects the pulse noise detected in the audio signal, for example, the sound of the “s” line or the cymbals of the music. It is determined that the audio signal is an erroneously detected audio signal.
- the delay unit 65, the comparator 66, and the pulse determination unit 63 indicate that “the composite signal is input, and the composite signal includes pulse noise at a position corresponding to the noise noise detected in the audio signal.
- a function of “pulse determination means” for determining that the detection result by the pulse detection means is valid is provided.
- the comparator 66 corresponds to “a first comparator that compares the amplitude of the input entire band of the composite signal with a first threshold value”, and the pulse determination unit 63 includes “the input composite signal. The detection result is determined to be valid when the amplitude of the signal exceeds the first threshold value at the position.
- the pulse suppressing unit 64 is “a pulse suppressing unit that suppresses pulse noise detected in the audio signal when the pulse determining unit determines that the detection result of the pulse detecting unit is valid”. For example, the detected pulse noise is suppressed by replacing the sample value of the audio signal in the pulse detection interval with the value of the sample immediately before the pulse detection interval.
- the delay unit 65 delays the composite signal output from the FM demodulation unit 4 by the processing time in the band limiting unit 5 and the pulse detection unit 62, and synchronizes the pulse detection signal and the composite signal.
- Comparator 66 compares the composite signal delayed by delay device 65 with a threshold value, and outputs the comparison result to pulse determination unit 63. For example, the comparator 66 is a comparison result between the composite signal and the threshold value.
- the pulse determination unit 63 when the pulse detection signal is, for example, a signal that is “1” in the state in which the pulse noise is detected and is detected and is “0” in the state, the pulse detection signal is detected.
- the logical product of the signal and composite signal is taken, and if the logical product is “1”, it is determined that the audio signal in the panorless detection section is pulse noise, and if the logical product is “0”, an error occurs. It is determined to be detection.
- the pulse detector 62 detects the pulse noise included in the monaural audio signal in a weak electric field, so that the influence of the background noise is less. Candidates can be detected. Further, the pulse determination unit 63 compares the amplitude of the composite signal synchronized with the audio signal with a threshold value, and verifies whether or not the pulse noise candidate detected by the pulse detection unit 62 is a false detection. Therefore, the audio signal force is not judged based on either the audio signal or the composite signal alone. The detected noise noise candidate is verified by looking at the amplitude of the composite signal. This has the effect that it can be determined.
- the threshold value to be compared with the amplitude of the composite signal may be a variable value according to the modulation rate of the FM signal.
- FIG. 6 is a block diagram illustrating a configuration of an FM radio receiver including the modulation rate detection unit 7.
- the modulation rate detection unit 7 has a function of “a modulation rate detection unit that detects a modulation rate of a frequency-modulated signal and generates the first threshold according to the detected modulation rate”.
- the FM demodulation unit 4 The modulation rate is calculated by, for example, averaging the amplitude of the composite signal output from the PC for a short time.
- the modulation rate detector 7 outputs a threshold voltage corresponding to the calculated modulation rate.
- the modulation rate detection unit 7 calculates a threshold voltage corresponding to the modulation rate by multiplying the calculated modulation rate by a predetermined threshold value.
- the comparator 66 indicates that “the modulation factor detecting means A function of the “first comparator” that compares the generated first threshold value with the amplitude of the composite signal is provided.
- the threshold value of the comparator 66 is variable according to the modulation rate, so that a more appropriate threshold value can be dynamically set without depending on the sound source. .
- the optimum threshold value in a region where the modulation rate is 100% modulation has a problem that the threshold value becomes too high in a region where the modulation rate is 50% modulation.
- the noise suppression unit 6 can effectively suppress pulse noise even when a vehicle equipped with an FM radio receiver moves between regions with different modulation rates. is there.
- FIG. 7 is a block diagram showing a configuration of an FM radio receiver including the composite processing unit 51.
- the preceding stage from the FM demodulator 4 is the same as the FM radio receiver shown in FIG.
- the FM radio receiver of Modification 2 includes an FM demodulation unit 4, a composite processing unit 51, and a noise suppression unit 60.
- the noise suppression unit 60 includes a delay unit 61, a pulse detection unit 62, a pulse determination unit 63, a noise suppression unit 64, a delay unit 65, a comparator 66, and a buffer 67.
- the composite signal is generally narrow-banded and further down-sampled inside the composite processing unit 51 as in the band limiting unit 5.
- the composite signal has a sampling frequency of 320 kHz, whereas the monaural audio signal has a sampling frequency of 40 kHz. Since this composite signal power composite processing unit 51 performs downsampling to 1Z8 by composite processing, there are 8 composite signals for one sample of monaural audio signal. Since the pulse detection signal is output for each sample of the monaural audio signal, there are 8 composite signals for each sample of the pulse detection signal. Therefore, as shown in FIG. 7, a buffer 67 is provided in front of the comparator 66. The buffer 67 holds 8 samples of the composite signal for 1 sample of the audio signal. As a result, the comparison by comparator 66 is performed for 8 samples per pulse detection signal. Make a decision. In this case, the noise determination unit 63 determines that the noise is pulse noise when, for example, even one of the 8 samples exceeds the threshold value.
- the noise suppression unit 60 of the first embodiment in this case, for example, it is verified whether 8 samples of the composite signal are pulse noise for one sample of the audio signal. Therefore, it is possible to determine and suppress pulse noise with higher accuracy.
- FIG. 8 is a block diagram showing a configuration of an FM radio receiver using the weak electric field pulse noise canceller according to the second embodiment of the present invention.
- the input to FM demodulator 4 is a BB signal as in Fig. 4.
- the FM radio receiver according to the second embodiment includes an FM demodulation unit 4, a composite processing unit 51, and a noise suppression unit 600.
- the noise suppression unit 600 determines the interval from the rising edge to the falling edge of the pulse detection signal as a pulse detection interval, and determines whether or not the signal detected as a noise noise candidate within this pulse detection interval is a pulse noise.
- the noise suppression unit 600 includes a delay unit 61, a pulse detection unit 62, a pulse determination unit 63, a pulse suppression unit 64, a delay unit 65, a comparator 66, a notafer 67, a delay unit 68, a delay unit 69, and a rising / falling detection. Part 70 is provided.
- the pulse detection unit 62 reads: “A high-pass filter (HPF 201 in FIG. 1) that receives the audio signal as input and a second comparator (comparison in FIG. 1) that compares the output of the high-pass filter with a second threshold value. 203), and a pulse detection that rises when the output of the high-pass filter exceeds the second threshold and falls when the output of the no-pass filter falls below the second threshold. It has the function of “the pulse detecting means for outputting a signal”.
- the rising Z falling detection unit 70 monitors a pulse detection signal output when a pulse noise candidate is detected by the pulse detection unit 62, and detects the rising and falling of the noise detection signal. That is, the rising Z falling detection unit 70 detects “rising and falling of the pulse detection signal output from the pulse detection means and detects in the audio signal. And a function of “rising z falling detecting section” for measuring the pulse noise interval.
- the rising Z falling detection unit 70 outputs a rising signal as the detection result when detecting the rising edge of the pulse detection signal, and outputs a falling signal as the detection result when detecting the falling edge of the pulse detection signal.
- the comparison of the amplitude of the composite signal by the comparator 66 starts with the rising signal output from the rising Z falling detection unit 70 and ends the comparison with the falling signal.
- the pulse determination unit 63 determines that the noise is pulse noise when, for example, even one sample exceeds the threshold within the pulse detection interval from the time when the comparison is started by the rising signal to the falling signal. That is, the pulse determination unit 63 indicates that “the composite signal corresponding to the interval measured by the rising Z falling detection unit has an amplitude that exceeds the first threshold more than a predetermined number of times.
- a function of the “pulse determination means” for determining that the detection result is valid is provided.
- the rising signal indicates the start point of one pulse noise
- the falling signal indicates the end point of the pulse noise
- the composite signal between the rising signal and the falling signal is the one pulse noise in the audio signal.
- the delay units 68 and 69 have the same number of delays, and delay the audio signal by the number of samples between the rising signal and the falling signal.
- the pulse suppressing unit 64 holds, for example, the value of the audio signal sample immediately before the rising edge of the pulse detection signal, and the audio signal from the rising edge to the falling edge of the noise detection signal.
- the pulse noise can be suppressed by holding the value of this sample and replacing it with a value.
- the rising and falling edge detection unit 70 detects the rising and falling edges of the pulse detection signal to measure the length of the pulse detection interval in which the pulse noise candidate is detected, and adding it to the determination condition makes it more accurate.
- High pulse noise determination can be performed.
- the pulse determination unit 63 is determined to be a pulse noise when one sample within the pulse detection interval in which a pulse noise candidate is detected exceeds the threshold and the pulse detection interval length of the pulse noise candidate is equal to or shorter than a predetermined length.
- FIG. 9 is a block diagram showing a configuration of an FM radio receiver that is a first modification of the second embodiment.
- the FM radio receiver is an FM radio receiver that suppresses pulse noise by using the pulse detection interval length in which a pulse noise candidate is detected as a judgment of the pulse judgment unit 63.
- a processing unit 51 and a noise suppression unit 610 are provided.
- the noise suppression unit 610 includes a delay unit 61, a pulse detection unit 62, a pulse determination unit 63, a pulse suppression unit 64, a delay unit 65, a comparator 66, a nother 67, a delay unit 68, a delay unit 69, and a rising / falling edge.
- a detection unit 70, a comparator 71, and an AND circuit 72 are provided.
- the comparator 71 does not compare the voltage values of two inputs, and the number of samples from the rising signal to the falling signal output by the rising Z falling detection unit 70, and a predetermined threshold value. (In the claim !, “Third threshold”). This threshold value is given as an integer of about 3 to 5, for example, because the number of pulse noise samples included in the audio signal is about 3 to 5 samples.
- Comparator 71 outputs ⁇ 1 '' when the number of samples until the falling signal is equal to or less than the threshold value for the rising signal power, and ⁇ 0 '' when the number of samples until the rising signal power exceeds the threshold value. Is output.
- the comparator 66 compares the amplitude of the composite signal of 8 samples with the threshold voltage for one sample of the pulse noise candidate, and outputs “1” when even one of the 8 samples exceeds the threshold. If one of the 8 samples of the composite signal is below the threshold, “0” is output.
- the AND circuit 72 outputs a logical product of the output of the comparator 66 and the output of the comparator 71.
- the pulse determination unit 63 represents a state in which the pulse detection signal output from the delay unit 69 has detected a pulse noise candidate. When the output from the AND circuit 72 is “1”, the pulse determination signal 63 is a candidate for pulse noise. It is determined that a certain sample is actual pulse noise, and when the output from the AND circuit 72 is “0”, it is determined that the pulse noise candidate is an erroneously detected audio signal.
- the comparator 71, the AND circuit 72, and the pulse determination unit 63 are described as "the rising Z falling detection.
- the pulse suppressor 64 holds the sample value of the audio signal immediately before the rising edge of the pulse detection signal, and the audio signal determined to be pulse noise in the section from the rising edge to the falling edge of the pulse detection signal. Hold the sample value and replace it with the value to suppress the pulse noise.
- noise suppression section 610 has a length of a section in which a pulse noise candidate is detected, that is, a section from the rising edge to the falling edge of the pulse detection signal. If it is longer than the pre-set threshold value (standard pulse noise pulse width), it is determined that it is not pulse noise, so it is possible to determine and suppress pulse noise more accurately. .
- one sample of an audio signal detected as a pulse noise candidate and one sample of the composite signal exceeds the threshold it is determined as pulse noise.
- the present invention is not limited to this. It is not limited. For example, it may be determined as pulse noise when a majority of composite signals exceed a threshold for one sample of an audio signal detected as a pulse noise candidate. Also, pulse noise may be determined when two or more consecutive samples (or a predetermined number of samples) of the composite signal exceed the threshold, and pulse noise may be detected when all the samples of the composite signal exceed the threshold. It may be judged.
- the comparator 71 compares the number of samples from the rising signal to the falling signal with the number of samples serving as a threshold, and it is not always necessary to compare with the number of samples.
- the time from the rising signal to the falling signal may be measured with a timer and compared with the threshold time.
- pulse suppression unit 64 suppresses the detected pulse noise by replacing the sample value of the audio signal in the pulse detection interval with the value of the sample immediately before the pulse detection interval.
- the noise noise may be suppressed by other methods. For example, the average value of the value of the sample immediately before the pulse detection interval and the value of the sample immediately after the pulse detection interval is obtained, and the pulse is calculated using that value.
- the sample value of the audio signal in the detection section may be replaced.
- the effectiveness of the pulse detection signal is determined by comparing the amplitude of the entire band of the composite signal with the threshold value. However, only the high frequency of the composite signal is compared with the threshold value to determine the pulse. You can judge the validity of the detection signal.
- the noise suppression unit 6 applies noise suppression processing (removal of weak electric field pulse noise) to the monaural audio signal output from the band limiting unit 5 and then the noise-suppressed monaural audio signal.
- noise suppression processing moving of weak electric field pulse noise
- FIG. 10 is a block diagram showing a configuration of an FM radio receiver including a weak electric field noise canceling unit 8 subsequent to the noise suppressing unit shown in FIG. The FM radio receiver shown in FIG.
- FIG. 10 includes an electric field strength measurement unit (not shown) that measures the received electric field strength of the FM radio signal received by the antenna 1 inside.
- the electric field strength measuring unit has a function of “electric field strength measuring means for measuring the electric field strength of the received audio signal”.
- FIG. 11 is a block diagram showing an internal configuration of the weak electric field noise canceling unit 8 shown in FIG.
- the weak electric field noise canceling unit 8 includes an FFT (fast Fourier transform) unit 80 1, a noise pattern storage unit 802, a subtractor 803 and an IFFT (inverse fast Fourier transform) unit 80 4.
- FFT fast Fourier transform
- IFFT inverse fast Fourier transform
- the audio signal output from the noise suppression unit of the present invention is a time-domain signal that can be reproduced as it is by outputting it directly to a speaker or headphones.
- noise cancellation by the weak electric field noise canceling unit 8 is performed by spectral subtraction in the frequency domain.
- the FFT unit 801 has a function of “a frequency converting unit that converts a time domain audio signal in which a pulse is suppressed by the pulse suppressing unit into a frequency spectrum in the frequency domain”, and outputs the audio signal output from the noise suppressing unit.
- the frequency domain spectrum is converted by high-speed Fourier transform.
- the noise pattern storage unit 802 is configured to display a noise pattern represented by a frequency spectrum for each electric field strength that is determined in advance. It has the function of “noise pattern storage means” to store the spectrum pattern of weak electric field white noise for each predetermined electric field strength.
- the subtractor 803 reads “a noise pattern corresponding to the electric field intensity measured by the electric field intensity measuring unit from the noise pattern storage unit and subtracts the frequency vector force obtained by the frequency converting unit”.
- the subtractor 803 subtracts the spectrum pattern of the weak electric field white noise read from the noise pattern storage unit 802 from the frequency spectrum frequency-converted by the FFT unit 8001.
- the spectrum pattern read out from the noise pattern storage unit 802 corresponds to the electric field strength when it is received as an audio signal power SFM radio signal that is a frequency spectrum to be subtracted from the spectrum pattern. That is, the electric field strength when reading the spectrum pattern from the noise pattern storage unit 802 is obtained by, for example, the average value of the received electric field strengths of audio signal samples for one frame, which is a unit of frequency conversion in the FFT unit 801. It is done.
- the IFFT unit 804 converts the frequency spectrum thus obtained into an audio signal in the time domain by inverse fast Fourier transform. That is, IFFT section 804 has a function of “inverse frequency conversion means for performing inverse frequency conversion of the frequency spectrum that is the subtraction result of the vector subtraction means into an audio signal in the frequency spectrum time domain of the frequency domain”.
- the time-domain audio signal output from IFFT section 804 is output to a speaker or headphones, etc., and reproduced as audio.
- the FM radio receiver weakens the audio signal from which weak electric field pulse noise has been removed by the noise suppression unit 6 by spectral subtraction in the frequency domain.
- a process of removing electric white noise is performed.
- pulse noise can be removed before applying spectral subtraction, so that it is possible to prevent an increase in the spectrum of the audio signal (a constant value addition) due to the spectrum of the pulse noise.
- weak electric field white noise can be removed with higher accuracy.
- the noise suppression unit 6 and the weak electric field noise canceller shown in FIG. 8 In the third embodiment, the noise suppression unit 6 and the weak electric field noise canceller shown in FIG. In the example in which the power unit 8 is combined, the weak electric field noise canceling unit 8 described above can obtain the same effect even when combined with the noise suppressing unit in any of the embodiments of the present invention.
- Embodiment 3 the case of converting a time-domain audio signal into a frequency-domain spectrum using Fast Fourier Transform is described.
- the frequency conversion method is as follows.
- other frequency transform methods such as DCT (discrete cosine transform) and M DCT (modified discrete cosine transform) may be used.
- each functional block after the FM demodulator 4 is typically a DSP mounted on an LSI that is an integrated circuit. (Digital Signal Processor) and software executed on DSP.
- the IF processing unit 3 may be mounted on the LSI according to circumstances. These may be individually chipped, or may be chipped to include some or all of them.
- a functional block other than a memory may be provided as a single chip!
- IC integrated circuit
- system LSI system LSI
- super LSI super LSI
- ULTRA LSI depending on the difference in power integration
- the method of circuit integration is not limited to LSI's, and implementation using dedicated circuitry or general purpose processors is also possible. It is also possible to use a field programmable gate array (FPGA) that can be programmed after LSI manufacturing, or a reconfigurable processor that can reconfigure the connection and settings of circuit cells inside the LSI.
- FPGA field programmable gate array
- each functional block may be configured by dedicated hardware that has power, such as a logic circuit.
- the noise suppression device of the present invention is useful as a sound quality improvement technique in an FM radio receiver.
- portable radios that cause a decrease in electric field strength due to movement of people or cars, It is suitable for sound quality improvement technology for radio receivers and in-vehicle radio receivers built into mobile phones.
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- Engineering & Computer Science (AREA)
- Signal Processing (AREA)
- Computer Networks & Wireless Communication (AREA)
- Noise Elimination (AREA)
Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
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JP2008512022A JP4531837B2 (ja) | 2006-04-24 | 2007-03-15 | 雑音抑圧装置 |
US12/294,314 US8050646B2 (en) | 2006-04-24 | 2007-03-15 | Noise suppressing device |
CN2007800114570A CN101411074B (zh) | 2006-04-24 | 2007-03-15 | 噪声抑制装置和噪声抑制方法 |
Applications Claiming Priority (2)
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JP2006-119560 | 2006-04-24 | ||
JP2006119560 | 2006-04-24 |
Publications (1)
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WO2007122923A1 true WO2007122923A1 (ja) | 2007-11-01 |
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PCT/JP2007/055266 WO2007122923A1 (ja) | 2006-04-24 | 2007-03-15 | 雑音抑圧装置 |
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US (1) | US8050646B2 (ja) |
JP (1) | JP4531837B2 (ja) |
CN (1) | CN101411074B (ja) |
WO (1) | WO2007122923A1 (ja) |
Cited By (2)
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JP2012100154A (ja) * | 2010-11-04 | 2012-05-24 | Japan Kyastem Co Ltd | 受信装置および受信方法、並びにプログラム |
JP2012147276A (ja) * | 2011-01-12 | 2012-08-02 | Fujitsu Ten Ltd | 受信装置およびインパルスノイズ除去方法 |
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EP2088786A1 (en) * | 2008-02-06 | 2009-08-12 | Sony Corporation | Method and receiver for demodulation |
WO2012098856A1 (ja) * | 2011-01-17 | 2012-07-26 | パナソニック株式会社 | 補聴器、及び、補聴器の制御方法 |
CN102130733B (zh) * | 2011-04-19 | 2013-07-03 | 中国电子科技集团公司第五十四研究所 | 一种无线电频谱感知的实现方法 |
TWI492622B (zh) * | 2011-08-31 | 2015-07-11 | Realtek Semiconductor Corp | 網路訊號接收系統與網路訊號接收方法 |
DE102012201372A1 (de) * | 2012-01-31 | 2013-08-01 | Sennheiser Electronic Gmbh & Co. Kg | Stationärer, analoger FM-Empfänger zum Empfangen von analogen, drahtlos übertragenen FM-Audiosignalen von mindestens einer mobilen Einheit und Verfahren zum Empfangen eines analogen, frequenzmodulierten Audiosignals von einem mobilen analogen FM-Sender |
CN104519447B (zh) * | 2013-10-08 | 2018-12-14 | 三星电子株式会社 | 降噪设备和方法以及具有无磁性扬声器的音频播放设备 |
KR102175163B1 (ko) * | 2013-10-08 | 2020-11-05 | 삼성전자주식회사 | 소음 제거 방법 및 장치와 무자석 스피커를 사용하는 음향 재생 장치 |
DE112016003942T5 (de) * | 2015-08-31 | 2018-05-24 | Asahi Kasei Microdevices Corporation | Demodulator |
JP6687453B2 (ja) * | 2016-04-12 | 2020-04-22 | パナソニック インテレクチュアル プロパティ コーポレーション オブ アメリカPanasonic Intellectual Property Corporation of America | ステレオ再生装置 |
US11296739B2 (en) * | 2016-12-22 | 2022-04-05 | Nuvoton Technology Corporation Japan | Noise suppression device, noise suppression method, and reception device and reception method using same |
EP3627853A4 (en) * | 2017-05-19 | 2021-02-24 | Audio-Technica Corporation | AUDIO SIGNAL PROCESSOR |
CN110832557B (zh) * | 2017-08-02 | 2022-04-19 | 欧姆龙株式会社 | 传感器装置、背景噪声数据发送方法和存储介质 |
US10419047B1 (en) * | 2018-12-19 | 2019-09-17 | Silicon Laboratories Inc. | Performing noise cancellation in radio signals using spectral duplication |
JP7078018B2 (ja) * | 2019-06-26 | 2022-05-31 | 株式会社Jvcケンウッド | 受信装置及び受信処理プログラム |
CN112235693B (zh) * | 2020-11-04 | 2021-12-21 | 北京声智科技有限公司 | 麦克风信号处理方法、装置、设备及计算机可读存储介质 |
FR3119056B1 (fr) * | 2021-01-15 | 2023-10-27 | Continental Automotive | Dispositif adaptatif de réduction du bruit d’un signal radio FM |
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- 2007-03-15 JP JP2008512022A patent/JP4531837B2/ja not_active Expired - Fee Related
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JP2012147276A (ja) * | 2011-01-12 | 2012-08-02 | Fujitsu Ten Ltd | 受信装置およびインパルスノイズ除去方法 |
Also Published As
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JPWO2007122923A1 (ja) | 2009-09-03 |
US20090274251A1 (en) | 2009-11-05 |
JP4531837B2 (ja) | 2010-08-25 |
CN101411074B (zh) | 2012-05-23 |
US8050646B2 (en) | 2011-11-01 |
CN101411074A (zh) | 2009-04-15 |
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