JPS5945725A - Impulsive noise reducing device - Google Patents

Abstract

PURPOSE:To attain excellent linear interpolation even if the existing period of an impulsive noise is long, by bringing a signal given to a sampling and holding circuit to the state that the phase is led by a desired angle of >=90 deg. than that of an output signal. CONSTITUTION:When the existing period of an impulsvie noise mixed to an input audio signal S1 is close to 1/4 cycle of a desired signal, a control signal S2 having a pulse width corresponding to the period when the impulsvie noise exists is generated from a control signal generating circuit CSG. On the other hand, an output signal from differentiating circuits 6, 11 is added by an adder 12 and a signal S4 having a desired lead angle of >=90 deg. that of a desired signal is obtained. Further, a sampling and holding circuit 7 supplies an output signal S5 to a signal compensating circuit 5 via a gain limit circuit 13. A compensating circuit 5 interpolates linearly a missing part of the signal during the existing period of impulsive noise with the signals S2 and S5, and outputs a signal S3 from a terminal 5b.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is directed to the prevention of pulse noise that is introduced from the outside into the audio signal system of audio equipment, radio receivers, pre-vision receivers, video disc players, etc. The present invention relates to a one-pressure reducing device for pulse noise, which allows audible and satisfactory reduction of pulse noise.

(Prior art) In the audio signal system of various equipment such as electric equipment or electronic equipment having an audio signal system, pulse noise, such as the noise of an automobile or pulses generated by other electro-printed equipment. It is well known that the quality of an audio signal deteriorates when artificial noise is mixed into the audio signal.

Conventionally, methods for reducing the quality deterioration of audio signals caused by the above-mentioned pulse noise include (a) reducing the gain of the signal transmission system during the period in which pulse noise occurs, or A method of attempting to reduce pulse noise by cutting off the transmission system (reducing the gain to zero... employing a squelch circuit), (b) reducing the signal level of the signal during the period of pulse noise, The most common method of noise reduction has been to try to reduce pulse noise by holding the signal level at the level just before the pulse noise period. ) and (b) have the disadvantage that the signal is lost during the period of pulse noise, and the noise reduction effect cannot be sufficiently obtained even by applying the above-mentioned means (a) and (b). The problem was that there wasn't one.

By the way, in order to interpolate the a) signal loss that occurs during the noise period, after converting the analog signal to a differential signal, a) Complement 1: Create a signal by applying the linear prediction method. Interpolation of the signal during the noise period using the correction peak signal has been adopted in some digital devices, but implementing this requires the use of complex and expensive circuits. VC, such solutions have not been applied to general audio equipment.

Now, as mentioned above, when the pulse noise mixed in the signal is reduced, the signal loss occurs corresponding to the period of existence of the pulse noise. The problem is that an audio signal of good quality cannot be obtained even with the reduction, and the use of complex and expensive circuits is required to interpolate the missing portions of the signal to solve the above-mentioned problems. The problem with this is that it is difficult to apply it to general audio equipment.

In order to solve the above-mentioned conventional problems, the applicant company first developed a differentiation circuit, a sample bold circuit, and a pulse <'<t= in the input audio signal.
, I JiJJ '7. ) Having slope information of the desired signal 4) Signals and control signals should be fed together.
(a) Easy to use, such as a signal correction circuit configured as (a), which removes pulse noise in manual audio details and linearly interpolates the desired signal during the period when pulse-like Mt sound is occurring. An analog Q circuit with a similar circuit configuration interpolates the missing part of the signal during the period when pulse noise occurs, and creates a supplementary signal such as (1), thereby obtaining a high-quality digital signal. We have developed a device that suppresses pulsed noise.

FIG. 1 is a block diagram of the previously proposed one-component device for pulseless noise blindness, and in this FIG. 2 is a delay circuit, and C8G is a control signal generation circuit composed of a ζ noise detection circuit 3 and a pulse shaping circuit 4. This control (S signal generation circuit C
From 8G, it is mixed into the input audio signal 81.
) 41 pulses 1J corresponding to the duration of pulse noise
A control signal 82 is generated.

As the pulse noise detection circuit 3 and the pulse shaping circuit 4 in the control signal generation circuit C8G, appropriate circuits may be selected from well-known configurations.

By the way, the control signal S2 generated from the control signal generation circuit C8G is required to correspond correctly to the position on the time axis of the pulse noise mixed in the input audio signal. In the generation circuit C8G,
Pulse noise mixed in the input audio signal is detected, and a) control signal S2 with a pulse width corresponding to the pulse width corresponding to the area where the pulse noise exists is generated according to 7'1. Since there is a predetermined time delay determined depending on the operating characteristics of the pulse noise detection circuit 3 used, the pulse noise mixed in the input audio signal and that pulse noise are different from each other. The input audio signal supplied to the input terminal 1 is delayed by the delay 9jEl1 having a delay time approximately equal to the IltIi4+ difference between the correspondingly generated control signal and the (-) control signal. -
The various signal processing to be performed by @S2 is performed correctly at the location where the -/responsive noise σ) exists in the input audio signal. The human input audio signal S1 indicated by a in FIG. signal S,
q): The position of the noise and the position of the control signal S2 on the time axis, shown by b in FIG. 2, correctly match.

Note that in FIG. 2, the time t is
, →t2, time t3→t4, time t, →tll each mJ
It is exemplified that l\=I is mixed with pulse noise N, I N21 N3.

In FIG. 1, one human-powered audio signal output from the delay circuit 2 is supplied to a signal correction circuit 50 at an input terminal 5aK. A concrete example of the configuration of the signal correction circuit 5 is shown in FIG. The control signal S2 generated by C8G is sent to the control signal input terminal 5.
c' and a signal 85 (e in Figure 2) having slope information of the desired signal is also supplied to the output terminal 5b (also σ in Figure 2) as shown in C. (S number S3, that is, the input audio signal S, v
The output signal S3 in the autumn state is sent out, in which the pulse noise at time c has been removed, and the desired signal has been linearly interpolated during the period in which the pulse noise occurred. The rules of the signal correction circuit 5 will be described later with reference to FIG.

The output signal S3 from the signal correction circuit 5 described above is output to the output terminal 8 of the device and is also supplied to the differentiating circuit 6. The differentiating circuit 6 differentiates the signal S3 indicated by CK in FIG. 2, and outputs a differentiated signal 84 as indicated by d in FIG.

The above-mentioned differential signal S4 is
) and the output signal 83 from the signal correction circuit 5.
It shows a phase difference of 0 degrees 7:, ), and the above equation 4
83, a signal section showing a constant a) signal level occurs corresponding to a signal section showing a constant slope (period in which pulse noise existed in the original signal). It is said that there is something like that.

Then, the signal 1/bell in the signal section showing the above-mentioned constant signal level in the differential signal 54Vc becomes a positive signal level or a negative signal level depending on the direction of the slope in the original signal. In addition, the polarity is changed depending on the direction of the slope of the original signal, and the signal level and zero level of the signal section showing a certain signal rail in the differential signal S4 are changed depending on the degree of slope of the original signal. The size of the gap is changing.

The differential output signal S outputted from the differentiating circuit 6 is supplied to the sample and hold circuit 7.
A signal S5 as shown in e of FIG. 2 is outputted from.

This signal S, when the device is operating in a steady state, is
This is the same as the first signal S4 described above. The sample and hold circuit 7 is unreliable for operation until the device enters steady state operation. As the →No=7 noring pulse for the sample pole 1-circuit 7 described above, the control signal S generated by the control signal generation circuit C8G is used.
2 is used.

Signal S5 output from the sample bold circuit 7
has a signal section showing a constant signal level that corresponds to a reliable section showing a constant signal level in the differential signal 54vc, as described above, and as described above, the differentiation sequence S, Since the signal section showing a constant signal level in indicates the slope information of the original signal (desired signal), the output signal S5 from the sample hold circuit 7 also shows the signal section showing a constant signal level. There are various information including slope information of the desired signal.

The signal correction circuit 5 outputs the signal S5 output from the sample and hold circuit 7, that is, the signal S having the slope information of the desired signal, to the terminal 5d of the correction circuit 5. Based on the slope information of the desired signal, a correction signal is created that can linearly interpolate the missing portion of the signal that occurred during the pulse noise mixing period in the input audio signal, and the missing portion of the signal is corrected using the correction signal. A linear interpolation is performed, and a signal S3 as shown in FIG. 2C is sent to the output terminal 8.

Next, with reference to FIG. 3, an example of the configuration of the differentiating circuit 6 and the sample and hold circuit 7, and the configuration and operation of the signal correction circuit 5 will be described. In the 31st curse, 7' otsuk 6
is a differential circuit 6, which is composed of a capacitor Cd, a resistor Rd, and an amplifier A3, and a sample-and-hold circuit 7 is composed of a switch SWs, a capacitor Cs, and an amplifier A. ing.

7a is a control signal S given as a sampling pulse.
The sample and hold circuit 7 holds the signal level immediately before the switch SWs is turned off during the no-no level period of the control signal S2, and the capacitor'tcsK switch SWs is turned off.

Block 5 is a signal correction circuit 5, in which 5a is an input terminal for an input audio signal, 5b is an output terminal, 5C is a control signal S20 supply terminal, and 5d is a supply terminal for a signal S. , and -A1 is a first amplifier, and A2 is a second amplifier, where the first amplifier A1 is of a low-power impedance, and the second amplifier A2 is of a high-input impedance.

A switch SW is provided in the signal transmission path between the output side of the first amplifier A1 and the input side of the second amplifier A2, and the switch SW is turned off when the control signal S2 is at the level 2. Furthermore, a charge storage capacitor C is provided between the input side of the second amplifier A2 and the ground, and a variable constant current circuit VC is provided on the input side of the second amplifier A20.
The output side of is connected.

In the example shown in FIG. 3, the variable constant current circuit VC includes a phase inversion amplifier -A with a gain of -1, a transistor X1 whose emitter is connected to a positive power supply -RQ)c via a resistor R1, The collector is connected to the collector of the transistor X, and the combing of the transistor X2 and the negative power supply -V
A resistor connected between DC and a positive power supply of 10V
It consists of a resistor R1 connected between DC and the negative power supply -VDC, a series connection circuit of a "J variable resistor" and a resistor R4, and the heath of the transistor X is connected to the resistor R3 and the variable resistor. (2), and the pace of transistor X2 is connected to the connection point between resistor R4 and variable resistor (2).

The variable resistor is used to correct imbalances in the circuit due to variations in the characteristics of the circuit components, and if the circuit can be balanced correctly, it can be replaced with two fixed resistors. .

The variable constant current circuit VC operates in a standard operating state such that when the voltage at its terminal 5d is 70, the voltage at two points is 0, and the voltage at the terminal 5d is positive. When the voltage at the two points is the same positive polarity as the voltage at the terminal 5d, and when the voltage at the terminal 5d is negative, the voltage at the two points is the same negative polarity as the voltage at the terminal 5d. Become.

Therefore, at two points of the variable constant current circuit VC, the signals S and Ic applied to the terminal 5d are constant signals -'f4 +/
Since a voltage appears with a polarity and a voltage value corresponding to the polarity and magnitude of the signal in the signal section indicating whether or not,
If a capacitor C is connected between the above two points and ground, the capacitor C will have the same polarity as the signal in the signal section showing a constant signal level at the signal MS,
The battery is charged with a constant charging current determined in accordance with the signal level of the signal section showing a constant signal level in the signal S5.

In the signal correction circuit 5 in FIG. 3, when the input audio signal S1 is not mixed with nipulse noise, the control signal s2 is supplied to the terminal 5cVLC. - level, the switch sw is turned on, and therefore, the input terminal 5a [supplied input audio signal S is the first amplifier A, -→switch SW-+the second
passing through the signal transmission path from amplifier A2 to output terminal 5b,
Transmitted from input terminal 5a to output terminal 5b. At this time, the charge storage capacitor C connected between the signal transmission path and the ground has a terminal voltage value according to the voltage value of the signal transmitted to the signal transmission path. Note that in the above state where no pulse noise is mixed in the input audio signal s1, the variable constant current circuit VC
The output terminal of is connected to the output side of the first amplifier A, which has an extremely low output impedance of approximately zero ohm, via the switch SW which is in the on state. A variable constant current circuit VCVtc is generated in response to a signal S, which is applied to the constant current circuit (2) via the terminal 5d, and the current output from the variable constant current circuit with high output impedance is approximately zero ohm as described above. Since the voltage generated by injection into the output side of the first amplifier AI, which has a low output impedance, is very small, the current generated from the variable constant voltage circuit VC described above is transferred from the first amplifier A1 to This does not cause any hindrance to the desired signal transmitted to the second amplifier A2. Therefore, as a signal to be supplied to the variable constant current circuit VC, there is no need to extract only the signal in the signal section that points to a constant signal level in the signal S, and to supply the signal to the variable constant current circuit VC. Current circuit ■-＼→)-Norhold circuit 7 output signal 8. may be supplied as is.

Next, when pulse noise is mixed into the input audio signal S, a control signal 82 is generated corresponding to the period in which the pulse noise N, to N3 is occurring, and the high level of the control signal S2 is generated. The switch SW is turned off for a period of time. By turning off the switch SW, the terminal voltage of the capacitor C is changed to the voltage at the terminal of the capacitor C.
The signal level is maintained at the time when the control signal S2 is turned off (when the control signal S2 is set to high level).

In addition, since the terminal 5d of the variable constant current circuit VC is given a signal in the signal section showing a constant signal level in the signal S in that state, the variable constant current circuit VC is connected to the terminal 5d. It outputs a current with a polarity that corresponds to the polarity of the given (S) and a constant current value that corresponds to the signal level, and the charge storage capacitor C is charged by hK. The charging operation for the charge storage capacitor C is performed over a period in which pulsed noise is occurring, and the terminal voltage of capacitor C increases linearly, but at the moment when the pulsed noise is no longer mixed in. I
C-System #] Signal S2 Pubba U-Rehel becomes switch S
Since W is in the on state, the accumulated charge in the capacitor C is instantly discharged by the low output innovitance of the first amplifier A.

The variable current circuit VC has a signal S1 supplied to the terminal 5d.
In other words, the signal S, which has slope information at a constant polarity and signal level in the desired signal, is driven by 1 from 2). A current with a constant polarity and a constant current value flows into the charge storage capacitor C, and the terminal voltage 4.
In the signal 85, the polarity of the signal in the signal section indicating the signal Lehar is raised linearly with an inclination centered on the Kagetsu rail, but the terminal voltage of 1 to Munico/Denoza C is variable constant current circuit. The terminal voltage of the core/tenza C before being raised by the inflow of current from the VC is the voltage of the human audio signal (U) just before the switch SW is turned on. Therefore, the omission of the signal No. 1 and No. 43 mixed into the input audio signal 81 and generated in the signal corresponding to the period of the single pulse noise is caused by the above operation of the signal correction circuit 5. It is clear that the signal 8 is well linearly interpolated and the signal 8 is sent out at the output terminal 9I/ilX.
3 has a waveform similar to that of the original Δase.

In FIG. 2, f shows the correction signal for linear interpolation created in the signal correction circuit 5 as a solid line! The waveform of the desired signal is shown by the dotted line, but f in Figure 2 makes it easier to understand the operation. In actual operation, the signal correction circuit 5 outputs a signal 8 as shown in C (・C) in FIG.
3 should be output.

(Problem to be solved by the invention F) This will be explained with reference to FIGS. 1 to 3. In the previously proposed pulse noise reduction device, No. 13 S3 is
), the differentiating circuit 6 shows a phase difference of 90 degrees with respect to the desired signal and the output signal 83 of the bias correction circuit 5, and also shows a phase difference of 90 degrees during the pulse noise mixing period. Kero desired conversion - Generates a differential signal S, which includes eye slope information, and calculates it in the pulse noise mixed period based on the slope information of the desired signal included in the above-mentioned differentiation @S. (1) Linear interpolation is performed for missing portions of the desired signal, and the previously proposed pulse noise reduction device is mixed into the audio signal. If the noise exhibits a period of existence that is significantly shorter than the period of the desired signal, the circuit operation described above can perform linear interpolation for the missing portion of the signal that occurs during the period of existence of the noculus noise. Pulse noise can be effectively reduced if it is performed well and does not cause any audible unnaturalness, but if the period of the pulse noise mixed into the input audio signal is equal to the period of the audio signal, then pulse noise can be effectively reduced. On the other hand, if the length is too long to ignore,1 in this case, the problem arises that linear interpolation for the missing portion of the signal cannot be performed satisfactorily during the existence period of the pulse noise.
The above problem occurs when the pulse noise exists for the same period, but when the frequency of the desired signal in the part (where the pulse noise is mixed) is a rough C, the pulse noise exists in the loop 1.
This is a major hindrance to performing good linear interpolation for the high frequency components of the desired signal, as the interval is relatively long with respect to the period of the desired signal. .

FIG. 4 is a diagram explaining the aforementioned problem in the previously proposed pulse noise reduction device shown in FIG. 1 (Part 3 (S)). Taking as an example the case where the pulse noise N has an existence period close to 1/4 of the period of the desired signal, the waveform of the signal showing the operation of the proposed device in that case is as follows. Fig. 4a shows a pulse noise N in the input audio (U), which has a period of existence close to 1/4 of the period of the input audio (U).
Figure 4 shows an example of the waveform of the input audio signal S1 on the input side where audio signal S1 is mixed.
A control signal is generated from the control signal generating circuit C8G in the circuit arrangement (C) shown in FIG. C in FIG. 4 is a waveform diagram of the differential signal S, which is output from the differential circuit 6 in the circuit arrangement shown in FIG. The signal S, which is output from the circuit 7 or C1, is commonly shown in this waveform diagram. Bold circuit 7 to Figure 1 (Figure 3)
5 is a waveform diagram of an output signal S3 that is supplied to the terminal 5d of the signal correction circuit 5 in the circuit arrangement lIt shown in FIG.

As is clear from the waveform diagram shown at a = d in FIG. 4, the reduction of pulse noise in the previously proposed circuit having the configuration shown in the circuit layout shown in FIG. 1 (FIG. 3) In the device, when the period of pulsed noise mixed in the human audio signal has a length K close to 1/4 of the period of the audio signal, the state of interpolation for signal loss during the period of pulsed noise becomes It has already been explained with reference to FIG. 2 that the result will not be as shown in the dotted line shown in d in FIG. 4 for reference, but as shown in the solid line in d in FIG. This is clear from the description of the circuit operation of the previously proposed device having the circuit arrangement shown in FIG. 1 (FIG. 3).

That is, in the circuit arrangement shown in FIG. 1 (FIG. 3),
As shown in FIG. 4A, for example, the input audio signal S1 has an existence period of about 1/4 period of the desired signal from the peak position of the desired signal. If the input audio signal S1 is mixed with pulse noise N, the beginning of the period of /ζ7-less noise N is the peak position of the input audio signal S1,
At the time when the slope of the signal on the time axis is O, the differential signal S4 output from the differentiating circuit 6 and the
・The output signal S from the circuit 7, the period information of the VC pulse noise +41/-, becomes O as shown in FIG. 4C, and the signal correction circuit 5 is not provided with slope information, interpolation for signal loss in the portion of the input audio signal S1 where the pulse noise N is mixed is based on the puffless noise N, as shown by the solid line in d of FIG.
At the beginning of the period, the signal level of the input audio signal 81 is maintained for 1/4 period of the desired signal.

Even if the start of the period of existence of the pulse noise mixed into the input audio signal is at the peak of the desired signal - 1 == i, the period of existence of the pulse noise mixed in the input audio signal is 1, 1 of the desired signal.
If it is significantly shorter than /4 period, the state in which the level of other layers of the desired signal is maintained at the peak value of the desired signal during that period will cause the signal to change during the period of pulse noise. This is to ensure that effective linear interpolation is being performed for the missing portion, but as mentioned above, the pulsed noise N
When the period of existence of the pulseless noise is long as shown in a of FIG. 4, the previously proposed puffless noise reduction device having the configuration shown in FIG. Therefore, good linear interpolation cannot be performed for the missing portion of the signal.

In explaining the problem with reference to FIG. 4, the desired signal is about 1.0 m from the peak position of the desired signal layer. For example, let's take the case where pulsed noise is mixed into the /4 period 7: ) part. Even if the waveform of the signal is different from the above, if pulse noise mixed into the desired signal exists for a long time, G is output from the differentiator circuit 6 and is differentiated by the in-differentiator (No. 8). However, the slope information contained in 84 will be insufficient, and linear interpolation of the signal in the missing portion of the signal during the presence of pulsed noise in the desired signal will still be inappropriate.

(First Means to Solve the Problem) The present invention provides a signal correction circuit that performs linear interpolation on the part of the desired signal where the signal is missing due to the inclusion of the pulse noise, even when the period of existence of the pulse noise is long. The Zambreholt circuit 7 is configured such that the signal S, which includes slope information, which can be well performed in the signal correction circuit 5, is supplied to the signal correction circuit 5.
7. The signal given to the output signal S3 is advanced by a required phase angle of 90 degrees or more.7. ) In order to prevent excessive linear interpolation of the signal due to the amplitude of high frequency components in the signal becoming too large due to the application of the above-mentioned means, a gain limiting circuit is provided. The purpose is to provide a pulse noise reduction device that satisfactorily solves the problems of the previously proposed pulse noise reduction device (as described above).

(Example) Next, specific contents of the pulse noise reduction device of the present invention will be explained in detail with reference to accompanying drawings.

FIG. 5 is a professional diagram of an embodiment of the pulse noise reduction device of the present invention, and in this fifth quotient, the pulse noise reduction device shown in FIG. Components that are the same as those in FIG. 1 are designated by the same drawing numerals as used in FIG.

In FIG. 5, ■ is an input terminal for the human audio signal S1 mixed with pulse noise, 2 is a delay circuit, and C8
G is a control signal generation circuit constituted by a pulse noise detection circuit 3 and a pulse shaping circuit 4, and from this control signal generation circuit C8G, an input audio signal is converted to -g.
S, [A control signal 82 having a pulse width corresponding to the period in which the mixed pulse noise exists is generated.

The delay circuit 2, signal correction circuit 5, first-order differential circuit 6-→J=unfold hold circuit 7, etc. in FIG. 5 will be explained with reference to FIG. 1 (FIG. 3). Delay circuit 2, signal correction circuit 5, and differentiation circuit 6 in the reduction device
, →No-pull bold circuit 7 and the like, respectively, and these components are explained in the description of the previously proposed pulse noise reduction device shown in Fig. 1 (Fig. 3). , the structure and operation are explained in detail.

In FIG. 5, the signal S3 sent from the terminal 5b of the signal correction circuit 5 to the output terminal 8 is connected to a first level setting device 9, which is provided at a position where the signal level is set in a predetermined manner. A second level setter 1 is provided at the first step to set the signal level in a predetermined manner.
0 to the second-order differentiator circuit 11 as a differentiated signal.

The L7.11th order differential signal outputted from the 11th order differential circuit 6 is the 1st order differential signal M S4. and the second-order differential signal S4□ outputted from the second-order differentiator circuit 11 are added by the adder 12. Although it is called signal S4, this addition signal S4 is a first-order differentiated signal 841 which is the sum of 90 degrees with respect to the differentiated signal S3, and a differentiated signal 83v.
Second-order differential signal S in a state of 1.80 degrees leading sum with respect to C
By adding 4□, the relationship between frequency convergence and phase shift angle becomes
J that shows the required change characteristics between 90 degrees and 180 degrees
It is considered to be a good thing.

FIG. 6 shows the desired signal, that is, the input audio signal S
, when the pulse noise mixed in the signal has a period of 100 microseconds, the missing portion of the constant signal that occurs in the desired signal-station during the pulse noise existence period is corrected by signal correction. L so that the input signal 85 to the signal correction circuit 5 required for outputting the signal S, which has been linearly interpolated well by the circuit 5, from the signal correction circuit 5 is obtained.
This shows the frequency versus phase shift angle characteristic of the addition signal S4 in the case where the addition signal S4 is used.

In order to make the frequency vs. phase shift angle characteristics (frequency vs. phase shift characteristics) of the summed signals S, VC even, it is necessary to perform linear interpolation for the missing portion of the desired signal that occurs during the presence of pulse noise. Depending on the length of existence of the pulse noise for which you want to perform well, or the frequency range of the desired signal for which you want to perform linear interpolation well, etc. It is determined.

FIG. 7 shows that, similar to the input audio conversion @S1 shown in the waveform diagram of a in FIG. Even if the signal is close to
2 and the added signal S4 is 90% higher than the desired signal.
A signal whose phase is advanced by a required angle greater than or equal to 100 degrees is obtained, and is given to the sample-and-hold circuit 7, and the output signal MS from the Samplepoort circuit 7 is sent to the signal correction circuit 5 via the limiter circuit 13, which will be described later. By supplying the signal to the terminal 5d, the missing part of the signal during the existence period of the pulse noise is linearly interpolated from the terminal 5b of the signal correction circuit 5. Figure 7 is a waveform diagram illustrating that a signal of 100 mm is obtained, and a in Figure 7 is a waveform diagram of an input audio signal in which pulse noise N is mixed. , b is the waveform (λ) of the control signal S2, and C in FIG. 7 is 1.4
7th waveform diagram of the additional W signal S4 and the output signal 85 from the Zumblebold circuit 7, which are adjusted to 0 degree advance phase.
d in the figure is a waveform diagram of the signal 83 outputted from the signal correction circuit 5 to the output terminal 8.

The waveform diagrams a to d of FIG. 7 are used to explain the operation of the device of the present invention, and the waveform diagrams of FIG. As is clear from the comparison between a and d, in the device of the present invention, the previously proposed device cannot perform linear interpolation well.1 Pulse noise N having such a long period of existence is mixed into the input audio signal. 1) Even in this case, the linear interpolation for the missing part of the signal is performed well during the existence period of the pulse noise. Problem A will be resolved successfully, so
.

Next, the gain limiting circuit 131' provided between the Zumblehold circuit 7 and the signal compensation circuit 5 will be explained. It is well known that the output from the differentiating circuit (the amplitude or wave of M M) becomes larger as the frequency of the signal to be differentiated becomes higher. It is also well known that if the differentiating circuit is a secondary image differentiating circuit, a larger differential signal will be output than if the differentiating circuit is a first-order image differentiating circuit.

By the way, in the apparatus of the present invention, as the addition signal 84, an addition signal S4 which is a sum of 99 degrees or more with respect to the signal to be differentiated is obtained, and the addition signal S4 is obtained so as to include the slope information that is required during horizontal line interpolation. The signal S is supplied to the signal correction circuit 5.

Accordingly, the high-frequency signal component of the differentiated signal S3 is generated by being differentiated; 1. - The sum signal S has a large peak value, and accordingly, the signal S4
The signal S having the same waveform as the terminal 5 of the signal correction circuit 5
dvc is applied and a linear interpolation operation is performed in the signal correction circuit 5. At this time, there is a signal for linear interpolation up to a portion K that exceeds the originally required linear interpolation portion. Output turbulent S where a correction error has occurred,
This results in the appearance of a), which causes noise in the birth sounds.

The gain limiting circuit 13 in FIG. 5 is provided to solve the above problem, and in this gain limiting circuit 13, the frequency of the desired delusion increases and the addition signal S
, the output signal S5 of the no-pull bold circuit 7 becomes sharp, but the sample hole size is limited so that it does not exceed a predetermined size. The signal is supplied to the terminal 5d of the supplementary circuit 5.

The line CL-CL, not shown in C of FIG. 7, indicates the limit value of the signal level by the L1 gain limiting circuit 13. A) You can use a slider of the configuration.
.

By providing the gain control circuit 13 as described above between the normal hold circuit 7 and the signal correction circuit 5, excessive linear interpolation that may occur in high-frequency, large-amplitude signal components can be avoided. The generation of noise can be effectively suppressed.

(Effects) As is clear from the detailed explanation above, the pulse noise reduction device of the present invention simply attenuates the gain of the transmission system during the period when puffless noise is mixed. As already mentioned, the signal level during the period of pulsed or puffless noise is maintained at the signal level of the signal immediately before the pulsed noise, thereby reducing the pulsed noise. 1. Unlike conventional pulse noise reduction devices, it also interpolates signal loss that occurs during pulse noise periods. 1. Pulse noise reduction without causing any audible unnaturalness. It is possible to perform this effectively (C), and even the circuit configuration for interpolating missing signals can be realized with a simple analog circuit. be able to provide it easily.

First, the pulse noise reduction device of the present invention has a sufficient correction effect not only when the time period during which pulse noise occurs is narrow, but also when the time period during which pulse noise occurs is wide. This eliminates ignition/ignition noise caused by automatic transmissions, autopi, etc., pulse noise generated from electric equipment with a built-in electric motor, and pop noise caused by dust or scratches on audio discs. , the troubles that occur when converting to audio when a video disc signal is missing!・Of course, it can be effectively applied to reduce noise and other pulse noise.

[Brief explanation of drawings]

Figure 1 is a 71 cock diagram of the previously proposed pulse noise reduction device, Figures 2, 4 and 7 are waveform diagrams for explaining the operation, and Figure 3 is a signal correction circuit and its related circuits. FIG. 5 is a circuit diagram of an example configuration of the pulse noise reduction device of the present invention. FIG. 6 is a characteristic diagram for explanation. Delay circuit, C8G, - Control signal generation circuit 53 - Pulse noise detection circuit, 4 - Pulse shaping circuit, 5 - Signal correction circuit, 6 - Primary image division circuit, 7 -> Non-pull hold circuit, 8 Output terminal, 9
．． 10... 1st. 2nd rail setter,]] Secondary e-divider circuit, 13...gain limiting circuit, VC...i-current circuit, C...charge storage capacitor, A1+A2
-First. Second amplifier, A3. A...Amplifier, S
W, SWs...Switch Patent Applicant Nippon Victor Co., Ltd. 2 Figure

Claims (1)

[Scope of Claims] 1. Means for detecting pulsed noise in an input audio signal containing pulsed noise and generating a control signal 18 having a pulse width corresponding to the period during which the pulsed noise occurs; a control signal generated by the control signal generating means described above in response to pulse noise in the input audio signal;
means for delaying an input audio signal containing pulsed noise by a delay circuit approximately equal to the time difference between the control signal and the corresponding pulsed noise; In addition to being supplied as a signal, a signal having slope information of a desired signal during a period in which pulsed noise occurs in the input audio signal is supplied, thereby performing a pulsed noise removal operation and generating pulsed noise. means for transmitting the output signal from the signal correction circuit to an output terminal; a means for supplying the output signal from the signal correction circuit to the first-order differentiator circuit via a second level setting circuit; means for adding the output signal and the output signal of the second-order differentiating circuit and then applying the control signal to the sample bold circuit, which is supplied as a sampling pulse; and means for applying the output signal of the sample bold circuit to the gain limiting circuit. and (a) means for causing the gain limiting circuit to output a signal having slope information of the desired signal during a period when pulse noise is occurring in the input audio signal, and supplying the signal to the signal correction circuit. The pulse noise reduction device 2 (as an S correction circuit, the charging operation using the output current of the variable constant current circuit for the charge storage capacitor is performed only during the period when the pulse noise is occurring; The pulse noise reduction circuit 3 according to claim 1 is configured such that a discharging operation is instantaneously performed at the end of the period, and the input serves as a preset reference as a gain limiting circuit. Pulse noise reduction device 4 according to claim 1, which uses a device configured to instantaneously perform gain limiting operation only for levels of 1 nm or higher.As a signal correction circuit, an output impedance a first amplifier with a low input impedance, a second amplifier with a high input impedance, and a period in which pulse noise is generated in a signal transmission path from the first amplifier to the second amplifier. The variable constant current is equipped with a switch circuit to cut off the S signal transmission, and operates so that the output current value is determined by a signal having slope information of the desired signal during the period when pulse noise is occurring. The output side of the circuit and the charge storage capacitor are connected to the input side of the second amplifier. 1 Pressure reducing device 5 As a variable constant current circuit, the current value is set according to the signal level of the input signal to it, and it is configured so that a constant current output with a polarity according to the polarity of the input signal to it can be obtained. %W [pulse noise reduction device according to claim 3]