JPS6325544B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is applicable to audio equipment, radio receivers, television receivers, video tape recorders,
The present invention relates to a pulse noise reduction device that can reduce pulse noise that has entered an audio signal system from the outside in a video disc player or the like in an audible manner.

(Prior art) Pulse noise, such as ignition noise of a car or pulse noise generated by other electrical equipment, is generated in the audio signal system of various equipment such as electrical equipment or electronic equipment that has an audio signal system. It is well known that if this happens, the quality of the audio signal will deteriorate.

Conventionally, methods for reducing the deterioration in audio signal quality caused by the above-described pulsed noise include (a) reducing the gain of the signal transmission system during the period in which pulsed noise occurs; Another method is to cut off the signal transmission system (lower the gain to zero...employ a squelch circuit) to reduce the pulse noise, and (b) reduce the signal level of the signal during the pulse noise period. 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 pulse noise period,
Also, by applying the above-mentioned measures (a) and (b),
The problem has been that a sufficient noise reduction effect cannot be obtained.

By the way, in order to interpolate the signal loss that occurs during the noise period, after converting the analog signal to a digital signal, a correction signal corresponding to the signal loss portion is created by applying the linear prediction method, and the correction signal is used to interpolate the signal loss that occurs during the noise period. Interpolation of signals during periods of noise is also used in some digital devices, but this requires the use of complex and expensive circuits. , 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 dropout will occur depending on the period of existence of the pulse noise. The problem is that it is not always possible to obtain an audio signal of good quality, and the use of complex and expensive circuitry is required to interpolate the missing portions of the signal to solve the above-mentioned problems. This means that the problem is that it is difficult to apply to general audio equipment.

In order to solve the above-mentioned conventional problems, the present applicant's company first uses a differentiating circuit, a sample hold circuit, and a signal having slope information of the desired signal during a period in which pulse noise occurs in the input audio signal. and control signals are supplied,
An analog circuit with a simple circuit configuration that includes a signal correction circuit that is configured to remove pulse noise in the input audio signal and linearly interpolate the desired signal during periods where pulse noise occurs. We proposed a pulse noise reduction device that uses a circuit to generate a correction signal that can interpolate the missing part of the signal during the period where pulse noise occurs, thereby obtaining a high quality audio signal. did.

FIG. 1 is a block diagram of the previously proposed pulse noise reduction device. In FIG. 1, 1 is an input terminal for an input audio signal S1 mixed with pulse noise, and 2 is a delay circuit. ,
CSG is a control signal generation circuit composed of a pulse noise detection circuit 10 and a pulse shaping circuit 11, and this control signal generation circuit CSG generates pulse noise mixed in the input audio signal S1. A control signal S2 is generated with a pulse width corresponding to the period in which .

The control signal S2 generated from the control signal generation circuit CSG described above is required to correspond correctly to the position on the time axis of the pulse noise mixed in the input audio signal. By the time the generation circuit CSG detects the pulse noise mixed in the input audio signal and generates the control signal S2 having a pulse width corresponding to the period in which the pulse noise exists, Since there is a predetermined time delay determined depending on the operating characteristics of the pulse noise detection circuit 10 used, the pulse noise mixed in the input audio signal and the pulse noise generated in correspondence with the pulse noise are generated. The input audio signal supplied to the input terminal 1 is delayed by the delay circuit 2, which has a delay time approximately equal to the time difference between the input audio signal and the control signal S2, and various signals to be performed by the control signal S2 are generated. Processing is performed correctly at the location of pulsed noise in the input audio signal.

The input audio signal S1 indicated by a in FIG.
The information input audio signal S1 is given a necessary time delay by the delay circuit 2, and the location of pulse noise mixed in the input audio signal S1 shown in a in FIG. 2; This corresponds correctly to the position on the time axis of the control signal S2 indicated by b in FIG.

In Fig. 2, for the input audio signal, time t1→time t2, time t3→time t4, time t5→
An example is shown in which pulse noises N1, N2, and N3 of each period of time t6 are mixed.

In FIG. 1, 3 is an amplifier with low output impedance characteristics, 4 is a switch that performs on/off operation according to the control signal S2, and 6 is used to store a correction voltage for linear interpolation operation. A capacitor 7 is a non-inverting amplifier (in-phase amplifier) having a gain G, and a capacitor 6 used to store a correction voltage for performing the linear interpolation operation described above is connected to the output side of the switch 4 and the non-inverting amplifier. (Common-mode amplifier) Connected between the signal transmission path between the input side of 7 and the ground,
Further, a feedback circuit including a resistor 8 and a capacitor 5 connected in series is provided between the output side and the input side of the non-inverting amplifier (in-phase amplifier) 7. 9 is an output terminal.

The switch 4 described above receives the input audio signal S1.
During the periods corresponding to the positions of the pulse noises N1, N2, and N3, the switch 4 is turned off by the control signal S2 generated by the control signal generation circuit CSG, and the switch 4 is turned off when the input audio signal It is turned on during a period when pulse noises N1, N2, and N3 are not present in S1.

Since the output impedance of the amplifier 3 is extremely low, the terminal voltage of the capacitor 6 when the switch 4 is turned on as described above is equal to the voltage of the input audio signal S1; It is output to the output terminal 9 via the non-inverting amplifier (in-phase amplifier) 7.

That is, when the switch 4 is turned on as described above, the input side of the non-inverting amplifier (in-phase amplifier) 7 is connected via the switch 4 to the output side of the amplifier 3, which has an extremely low output impedance. Therefore, the feedback circuit consisting of the series connection circuit of the resistor 8 and the capacitor 5 connected between the output side and the input side of the non-inverting amplifier (in-phase amplifier) 7 stops operating as a feedback circuit. Therefore, as mentioned above, the terminal voltage of the capacitor 6 connected to the input side of the non-inverting amplifier (common-mode amplifier) 7 is applied to the output terminal 9 via the non-inverting amplifier (common-mode amplifier) 7. It is output.

Next, when the switch 4 is turned off by the control signal S2 generated by the control signal generation circuit CSG during the period corresponding to the positions of the pulse noises N1, N2, and N3 in the input audio signal S1. , the voltage of the input audio signal S1 immediately before the switch 4 is turned off is stored in the capacitor 6.

The terminal voltage stored in the capacitor 6 described above is amplified by a non-inverting amplifier (in-phase amplifier) 7 with a gain of G and is outputted, and at the same time is amplified and outputted via a feedback circuit consisting of a series connection circuit of a resistor 8 and a capacitor 5. and is fed back to the input side of the non-inverting amplifier (in-phase amplifier) 7. Then, due to the feedback operation by the feedback circuit described above, the non-inverting amplifier (common mode amplifier) 7
The output voltage of the capacitor 5 and the capacitor 6 is divided by the capacitor 6 and stored in the capacitor 6, and the feedback operation described above is repeated during the noise period. teeth,
As will become clear from the analysis results described below using mathematical formulas, it functions as a differential feedback circuit, so the output side of the switch 4, which is turned off during the period when noise is present in the input audio signal S1, and the output terminal 9 performs the same function as a differentiating circuit, so that the output signal of the non-inverting amplifier (in-phase amplifier) 7 in the previously proposed pulse noise reduction device shown in FIG. The input audio signal S, such as the signal S3 shown in
The existence period of the noise in 1 is sent to the output terminal 9 as a linearly interpolated signal S3.

Next, a of FIG. 3 shows a circuit diagram of a circuit portion corresponding to a circuit portion that performs a linear interpolation operation in the already proposed pulse noise reduction device shown in FIG. switch in a of
Referring to Fig. 3 b, etc., which shows the circuit diagram in the frequency domain when the SW is in the OFF state,
The circuit between the output side of the switch 4 and the output terminal 9, which is in an OFF state during the period when noise is occurring in the input audio signal S1, is used to perform the above-mentioned operation during the period when noise is present in the input audio signal S1. The details of the linear interpolation operation will be explained using mathematical formulas.

First, clarifying the correspondence between each component in the circuit layout shown in FIG. 3a and each component in the circuit layout shown in FIG. In each component, amplifier A1 (a in Figure 3), amplifier 3 (Figure 1), switch SW (a in Figure 3) and switch 4 are connected.
(Fig. 1), non-inverting amplifier (common-mode amplifier) A2 (a, b in Fig. 3) and non-inverting amplifier (common-mode amplifier) 7
(Fig. 1), capacitor C1 (a in Fig. 3) and capacitor 5 (Fig. 1), capacitor C2 (a in Fig. 3) and capacitor 6 (Fig. 1), resistor R (a in Fig. 3). ) and the resistor 8 (FIG. 1) correspond to each other.

As mentioned above, when there is no noise in the input audio signal S1, the switch SW at a in FIG. 3 is in the on state,
The input signal V is applied to the input side of a non-inverting amplifier (in-phase amplifier) A2 via an amplifier A1 and a switch SW. to be turned off.

Now, let us assume that the terminal voltages of capacitors C1 and C2 immediately before the switch SW is turned off are e10 and e20, respectively.
When determining the output signal Vo(s) when the SW is turned off, the output signal Vo(s) is expressed as the following equation (1).

Vo(s) = (R+1/C1S+1/C2S) I(s) +e10/S+e20/S...(1) And the current I(s) flowing through the resistor R is I(s) = C1・C2{Vo(s) ) S−e10−e20}/C1+C2+C1・
It can be expressed as C2RS…(2).

Therefore, the input signal Vi(s) is expressed by the following equation (3).

Vi(s)=C1・Vo(s)S−C1・e10+C2・e20+C1・
C2・RS.e20/S(C1+C2+C1・C2・RS)…(3) Now, if the gain of non-inverting amplifier (in-phase amplifier) A2 is G, the output signal Vo(s) is Vo(s)=GVi( s) ...(4) Since it is shown by equation (4), the above (3),
From equation (4), the output signal Vo(s) is expressed by equation (5) below.

Vo(s) = G・(C1・C2・RS+C2)e20−C1・e10/S
{(1-G)C1+C2+C1・C2・RS}…(5) Here, if the capacitor C2 is selected as shown in equation (6), the output signal Vo(s )teeth,
When T1=C1·R, it is expressed by the following equation (7).

Vo(s) = G{e20/S+(G-1)e20-e10/(G-1)T
1・S ² ...(7) If the time just before the switch SW is turned off is t1, the signal voltage is V(t1), so the terminal voltages e10, e20 of capacitors C1 and C2
is expressed by the following equation (8).

e10=(G-1){V(t1)−V'(t1)} e20=V(t1)...(8) Substituting equation (8) into equation (7) above, the output signal Vo(s ) is shown by the following equation (9),
Moreover, when formula (9) is inversely transformed into Laplace, it becomes what is shown by formula (10).

Vo(s)=G{V(t1)/S+V'(t1)/S ² }...(9) Vo(t)=G{V(t1)+V'(t1)(t-t1)}...(10 ) Since Equation (10) above omits the second-order differential term and lower parts of the Taylor series, the linear interpolation circuit in the already proposed pulse noise reduction device shown in Fig. 1 is Non-inverting amplifier (common mode amplifier)
7. The gain of {corresponding to the non-inverting amplifier (in-phase amplifier) A2 shown in a and b of FIG.
Then, the capacitance value C2 of capacitor 6 {corresponding to capacitor C2 shown in a of FIG. 3} is changed to capacitor 5 {corresponding to capacitor C1 shown in a of FIG. 3}. The capacitance value C2 of the capacitor 6, which is (G-1) times the capacitance value C1 of It can be seen that when C1 is satisfied, a linear interpolation operation is performed in which the slope of linear interpolation is given by V'(t1), that is, the first-order differential voltage.

(Problems to be Solved by the Invention) In the previously proposed pulse noise reduction device explained with reference to FIGS. When the noise level ratio is small and white noise with a relatively high signal level exists in the high range of the audio frequency band, the slope of the signal fluctuates due to the white noise present in the high range. As a result, a malfunction occurs in the interpolation operation performed during the period when pulse noise occurs, and not only does the interpolation of the signal during the period of signal loss not occur correctly.
Due to problems such as the generation of new noise that follows the randomness of white noise, conventional devices cannot be applied well to signals from signal sources with a small signal level to white noise level ratio. The drawback was that I couldn't do it.

Furthermore, the conventional device does not perform the above-mentioned processing even when the signal to be processed is a so-called pre-emphasized signal, that is, a signal in which the high-frequency components of the signal are emphasized. The same disadvantages arise as in the case of a signal from a signal source with a small signal level to white noise level ratio.

Next, this point will be explained with reference to FIG. FIG. 4 is a block diagram showing a schematic configuration of a signal recording and transmission system that records or transmits audio signals as frequency modulated waves. In FIG. 13 is a pre-emphasis circuit having pre-emphasis characteristics as shown by the curve in FIG. 5, 14 is a frequency modulator, 15 is a recording medium or transmission line, 16 is a demodulation circuit, 17 is a de-emphasis circuit, 18 is an output terminal, which is connected to the de-emphasis circuit 17 described above.
The de-emphasis characteristic is as shown, for example, by the curve in FIG. 5, but as is well known, the pre-emphasis characteristic and the de-emphasis characteristic shown above exhibit complementary symmetry with each other. ing.

Now, in the recording or transmission system shown in Fig. 4, the above-mentioned pulse noise may be generated in the signal reproduced from the recording medium or the signal transmitted through the transmission path. When applying a reduction device, it is necessary to provide an audio signal before being de-emphasized, such as the output signal from the demodulation circuit 16, as an input signal to the pulse noise reduction device. It is said that

In other words, a signal containing pulsed noise is
The pulse noise in the signal de-emphasized by the de-emphasis circuit 17 and output from the de-emphasis circuit 17 is in a state where the noise time width of the pulse noise is expanded due to the de-emphasis characteristic as shown in the curve in FIG. Therefore, if the output signal from the de-emphasis circuit 17 is applied to a pulse noise reduction device configured as described above, it will be difficult to perform a good interpolation operation on the signal. be.

Therefore, the signal to be given to the pulse noise reduction device must be the audio signal obtained from the signal transmission path to the input side of the de-emphasis circuit, but the signal must be the audio signal before de-emphasis is applied. is in a state where its high-frequency components are pre-emphasized and are emphasized, so when a signal in such a state is supplied to the pulse noise reduction device described above, It will be well understood from the foregoing explanation that in a pulse noise reduction device, it is not possible to perform an interpolation operation satisfactorily during a period in which pulse noise occurs in a signal.

As is clear from the above description, in the conventional pulse noise reduction device described above, in the case of a signal that is pre-emphasized from a signal source with a small signal level to white noise level ratio, Because of the difficulty in performing good interpolation operations, a solution was sought.

(Means for Solving the Problems) The present invention detects pulse noise in an input audio signal including pulse noise, and generates a control signal having a pulse width corresponding to the period in which the pulse noise occurs. and a control signal generated by said control signal generating means corresponding to the pulsed noise in the input audio signal, and the time difference between said control signal and the corresponding pulsed noise. Means for delaying an input audio signal containing pulsed noise by a delay circuit having an equal delay time, the control signal as described above is supplied as a timing signal for operation, and the pulsed noise in the input audio signal is delayed. By supplying a signal having slope information of the desired signal during the period in which pulse noise occurs, it is possible to perform a linear interpolation operation on the desired signal during the period in which pulse noise is occurring, and also to perform linear interpolation on the desired signal during the period in which pulse noise is occurring. During the period when there is no pulse noise,
A pulse noise reduction device comprising a linear interpolation circuit and a de-emphasis circuit that are configured to always perform a de-emphasis operation, and as a circuit that combines the linear interpolation circuit and the de-emphasis circuit. , supplies an input audio signal to the inverting amplifier via the first resistor, and is connected to the second resistor between the input and output of the inverting amplifier and is turned on during a period in which pulse noise is occurring. A parallel connection circuit with the switch circuit of A first capacitor is connected between the input side of the above-mentioned inverting amplifier and the input side of the above-mentioned non-inverting amplifier, and furthermore, a first capacitor is connected between the input side of the above-described non-inverting amplifier. The present invention provides a pulse noise reduction device using a circuit in which a second capacitor and a third resistor are connected in series.

(Example) Hereinafter, specific contents of the pulse noise reduction circuit of the present invention will be explained in detail with reference to the accompanying drawings. FIG. 6 is a block diagram of an embodiment of the pulse noise reduction device of the present invention, and a in FIG. 7 shows the reduction of the pulse noise shown in FIG. FIG. 7b is an equivalent circuit diagram of the apparatus, and FIG. 7b is an equivalent circuit diagram of the pulse noise reduction apparatus shown in FIG. 6 in an area where pulse noise exists.

In the block diagram of one embodiment of the pulse noise reduction device of the present invention shown in FIG.
is an input terminal of the input audio signal S1 mixed with pulse noise, 20 is a delay circuit, and CSG is a pulse noise detection circuit 32 and a pulse shaping circuit 33.
The control signal generation circuit CSG generates a control signal S2 having a pulse width corresponding to the period in which pulse noise mixed in the input audio signal S1 exists. is generated.

As described above with reference to FIG. 2, the control signal S2 generated from the control signal generation circuit CSG is based on the time axis of the pulse noises N1, N2, and N3 mixed in the input audio signal S1. Although it is necessary to correctly correspond to the above position, in the control signal generation circuit CSG, the pulse noise N1 mixed in the input audio signal S1,
N2 and N3 are detected, and control signals S2 with pulse widths corresponding to the periods in which the pulse noise exists, time t1 → time t2, time t3 → time t4, and time t5 → time t6, are generated accordingly. By then, a predetermined time delay determined depending on the operating characteristics of the pulse noise detection circuit 32 used has occurred, so that the pulse noise N1, N2, N3 mixed in the input audio signal S1 and , its pulsed noise N1,
The input audio signal S1 supplied to the input terminal 19 is delayed by a delay circuit 20 having a delay time approximately equal to the time difference between N2, N3 and the correspondingly generated control signal S2, thereby generating the control signal S1 as described above. Various signal processing to be performed by S2 is
Pulse noise in input audio signal S1
Make sure that it is performed correctly at the locations of N1, N2, and N3.

In FIG. 6, 21 is an amplifier having low output impedance characteristics, and the output signal of this amplifier 21 is applied to an inverting amplifier 23 via a first resistor 22 (resistance R11). A second resistor 24 is connected between the input and output terminals of the inverting amplifier 23 described above.
(resistor R12) and a parallel connection circuit of the first switch circuit 25 are connected. The first switch circuit 25 described above is a switch circuit that is turned on during a period when pulse noise is present in the input audio signal S1.

Further, between the output side of the above-mentioned inverting amplifier 23 and the input side of the non-inverting amplifier 28, a second signal is connected between the output side of the inverting amplifier 23 and the input side of the non-inverting amplifier 28. switch circuit 2
7 is connected.

The first and second switch circuits 25 and 27 described above
The opening/closing control operation is performed by the control signal generation circuit described above.
This is carried out based on the control signal S2 generated by the CSG, and the opening/closing control signal supplied to the first switch circuit 25 is controlled by the control signal generating circuit.
Control signal S2 generated by CSG is transferred to inverter 3
4 with the polarity reversed.

A first capacitor 26 (capacitor C11) is connected between the input side of the non-inverting amplifier 28 and the input side of the inverting amplifier 23, and a first capacitor 26 (capacitor C11) is connected between the input and output terminals of the non-inverting amplifier 28. for,
A series connection circuit of a second capacitor 29 (capacitor C12) and a third resistor 30 (resistance R13) is connected.

In the pulse noise reduction device of the present invention having the above-described configuration, during a period (steady operation period) in which pulse noise does not occur in the input audio signal, the first pulse noise reduction device in the pulse noise reduction device
The second switch circuit 25 is turned off, and the second switch circuit 27 is turned on. In this state, the amplifier 23
Since the output impedance of is extremely low, the positive feedback circuit formed by the series connection circuit of the third resistor 30 and the second capacitor 29 stops operating, and the pulse noise reduction device shown in FIG. The amplifier 23 operates as an inverting amplifier, and the output from the amplifier 23 is sent to the output terminal 31 via the amplifier 28.

The transfer function G(s) for the equivalent circuit shown in FIG. 7a is determined as follows.

G(s)=-G.R12/R11.1/1+TS (11) where G is the gain of the amplifier 28, T is the time constant, and is expressed as T=C11.R12.

That is, in the period when no pulse noise exists in the input audio signal, the pulse noise reduction device shown in FIG. 6, which is represented by the equivalent circuit a in FIG. Therefore, it operates as a de-emphasis circuit exhibiting de-emphasis characteristics with a time constant of T=C11·R12.

Next, in the pulse noise reduction device shown in FIG. 6 during a period when pulse noise exists in the input audio signal, the first switch circuit 25
is turned on and the second switch circuit 27 is turned off, so in this state the amplifier 23 is short-circuited between its input and output terminals by the first switch circuit 25 which is turned on. As a result, the amplification action is stopped, and both the input and output terminals of the amplifier 23 become ground potential, and the first capacitor 26 becomes equivalent to having one end thereof grounded.

Therefore, the pulse noise reduction device shown in FIG. 6 during a period when pulse noise exists in the input audio signal is represented by an equivalent circuit as shown in FIG. 7b. , the equivalent circuit shown in FIG. 7b is an equivalent circuit for the period during which pulsed noise exists in the input audio signal in the already proposed pulsed noise reduction device explained with reference to FIG. The circuit is the same as the equivalent circuit shown in FIG. 3b.

Here, consider the terminal voltages of the capacitors C11 and C12 immediately before the second switch circuit 27 is turned on. First, capacitor 2
6, C11 has one end connected to the inverting input terminal side of the inverting amplifier 23, and the de-emphasized signal Vd (t1) is applied to the other end, so the capacitor 26, C11 The terminal voltage e20 is: e20=Vd(t1)...(12) Also, the terminal voltage e1 of the capacitor 29, C12
0 is shown in the following (13).

e10=(G-1) {Vd(t1)−V'd(t1)}...(13) The terminal voltage e20 of capacitor 26 and C11 shown by equation (12) and the voltage e20 shown by equation (8) mentioned above. Comparison with terminal voltage e20 of capacitor 2, C2, and
Comparing the terminal voltage e10 of capacitor 29, C12 shown by equation (13) with the terminal voltage e10 of capacitor 1, C1 shown by equation (8) already mentioned, we find that in equation (8), Equation (12) is obtained by replacing V(t1) and V′(t1) with Vd(t1) and V′d(t1), respectively.
It can be seen that Equation (13) is obtained.

That is, the pulse noise reduction device of the present invention operates as a de-emphasis circuit during a period when pulse noise is not present in the input audio signal, and operates as a de-emphasis circuit during a period when pulse noise is present in the input audio signal. During this period, it operates as a linear interpolation circuit that receives the de-emphasized signal as input, thereby greatly reducing pulse noise contained in the input audio signal.

(Effects) As is clear from the above detailed explanation, the pulse noise reduction device of the present invention simply attenuates the gain of the transmission system during the period when pulse noise is mixed, or , the signal level during the pulse noise period is maintained at the signal level immediately before the pulse noise, thereby reducing the pulse noise using the conventional method described above. Unlike a reduction device, since it also interpolates the signal loss that occurs during the period of pulse noise, it is possible to effectively reduce pulse noise without causing any unnaturalness to the auditory sense. Furthermore, since the circuit configuration for interpolating missing signals can be realized with a simple analog circuit, it is possible to easily provide audio equipment with excellent performance at low cost.

Furthermore, even if the white noise level input to the pulse noise reduction device of the present invention is relatively high, the high-frequency white noise level enhanced by the differentiating circuit can be reduced by switching the de-emphasis circuit. As a result, malfunctions caused by interpolation operations in signal correction circuits can be greatly reduced, and pulse noise can be easily reduced, which has a wider range of applications than conventional devices, and is useful for FM broadcast reception. Not only does it successfully reduce ignition noise from cars and motorcycles, which sometimes causes problems, and pulse noise generated from electrical devices with built-in motors, but it also reduces dust and dirt adhering to audio disks. Of course, the present invention can also be effectively applied to the reduction of pop noises caused by scratches, etc., dropout noises that occur in audio signals when a video disc signal is missing, and other pulse noises.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the previously proposed pulse noise reduction device, Figure 2 is a waveform diagram for explaining operation, Figure 3 is an equivalent circuit diagram of the previously proposed pulse noise reduction device, and Figure 4 is A block diagram of an example configuration of an FM signal recording and transmission system, FIG. 5 is a curve diagram of an example of pre-emphasis characteristics and de-emphasis characteristics, FIG. 6 is a block diagram of the pulse noise reduction device of the present invention, and FIG. 7 is a diagram of the present invention. FIG. 2 is an equivalent circuit diagram of a pulse noise reduction device of FIG. 1, 19... Input terminal, 2, 20... Delay circuit, CSG... Control signal generation circuit, 3, 7, 23,
28...Amplifier, 10,32...Pulse noise detection circuit, 9,31...Output terminal, 11,33...
Waveform shaping circuit, 4, 25, 27... Switch circuit, 5, 6, 26, 29... Capacitor, 8, 2
2, 24, 30...Resistor, 34...Inverter.

Claims (1)

[Scope of Claims] 1. Means for detecting pulsed noise in an input audio signal containing pulsed noise and generating a control signal having a pulse width corresponding to the period during which the pulsed noise occurs; A delay circuit having a control signal generated by the control signal generating means described above in response to pulsed noise in an audio signal, and a delay time approximately equal to the time difference between the control signal and the corresponding pulsed noise. means for delaying an input audio signal containing pulsed noise by;
The aforementioned control signal is supplied as a timing signal for operation, and a signal having slope information of the desired signal during a period in which pulsed noise occurs in the input audio signal is supplied, thereby reducing pulsed noise. It is configured to be able to perform a linear interpolation operation on the desired signal during the period in which it is occurring, and also to be able to perform a de-emphasis operation at all times during the period when no pulse noise is occurring in the input audio signal. This is a pulse noise reduction device equipped with a circuit that functions as a linear interpolation circuit and a de-emphasis circuit. In addition to supplying the signal, a parallel connection circuit is connected between the input and output of the above-mentioned inverting amplifier, and the second resistor and the first switch circuit that is turned on during the period when pulse noise is generated; , a second switch circuit that is turned off during the period in which pulse noise is occurring is connected between the output side of the inverting amplifier described above and the input side of the non-inverting amplifier; A first capacitor is connected between the input side of the amplifier and the input side of the non-inverting amplifier, and a second capacitor and a third resistor are connected in series between the input and output of the non-inverting amplifier. A pulse noise reduction circuit formed by connecting a connecting circuit. 2. A patent using a linear interpolation circuit in which the reciprocal of the voltage division ratio of the feedback voltage by the first capacitor and the second capacitor is set equal to the gain of the non-inverting amplifier. A pulse noise reduction device according to claim 1.