JPH04326294A - Frequency band dividing device - Google Patents

Abstract

PURPOSE:To provide the frequency band dividing device which prevents an over output for speaker drive or the like and does not increase the level of output synthesization near a divided frequency. CONSTITUTION:The outputs of a low-pass filter 2 and a high-pass filter 7 are converted to signals having original flat frequency characteristics by filters 4 and 9 with respectively reverse characteristics, and the outputs of the filters 4 and 9 are respectively detected by envelope generating means 5 and 10 so as to generate envelope signals. According to these respective envelope signals, level control means 3 and 8 are controlled and the output signals of the low-pass filter 2 and the high-pass filter 7 are outputted while respectively suppressing the levels at level control means 3 and 8.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency band dividing device used for speaker drives and the like.

0002

2. Description of the Related Art FIG. 4 shows the configuration of a conventional frequency band division device. In FIG. 4, 41 is an input terminal,
Input end of low-pass filter 42 and high-pass filter 47
are commonly connected to the input ends of the

43 introduces the input of a low-pass filter 42, and when the output of the low-pass filter 42 exceeds a threshold voltage, a level control means 44 for controlling the level of the signal is detected, and the level of the detected signal is controlled. a compressor 46 comprising envelope generating means 45 for applying to means 44;
is a low frequency output terminal that takes out the low frequency output of the compressor 43 and leads it to a speaker or the like.

On the other hand, 48 is a level control means 49 which introduces the output of the high-pass filter 47 and controls the level of the signal.
and an envelope generating means 50 that detects a signal exceeding the threshold voltage of the high-pass filter 47 and supplies the detected signal to the level control means 49,
Reference numeral 51 is a high frequency output terminal for extracting the high frequency output of the compressor 48 and guiding it to a speaker or the like.

Next, the operation of the above conventional example will be explained. In FIG. 4, when an audio signal is input to the input terminal 41, first the low-pass filter 42 and the high-pass filter 47
The signal is divided into two frequency bands, and the respective output signals are input to compressors 43 and 48, respectively.

[0006] In the compressor 43, the signal level is detected by the envelope generating means 45, and a signal exceeding the threshold voltage is detected by the envelope generating means 45, and the detected signal is given to the level controlling means 44. A signal exceeding the threshold signal is suppressed by the level control means 44, and a low frequency signal is taken out from the low frequency output terminal 46.

Similarly, in the compressor 48, the level of the high-frequency signal inputted from the high-pass filter 47 is detected by the envelope generating means 50, and the detected signal exceeding the threshold voltage is detected by the envelope generating means 50 and the level control means. 4
9, the signal exceeding the threshold signal is suppressed by the level control means 49, and the high frequency signal is taken out from the high frequency output terminal 51.

[0008] In this manner, the conventional frequency band dividing device described above also suppresses excessive output levels exceeding the threshold value for each divided frequency band, and connects the low frequency output terminal 46 and the high frequency output terminal 51 onwards. It is possible to protect audio equipment such as speakers.

[0009]

[Problems to be Solved by the Invention] However, in the above-mentioned conventional frequency band division device, the compressors 43, 48
As shown in FIG. 5, since the frequency response is flat, an operation is performed to expand the band of the frequency-divided signal for the input signal 52 exceeding the threshold value 53, and the frequency band division device When used as
As shown in FIG. 6, there is a problem in that the combined signal 63 of the two outputs 61 increases in level by more than the threshold value 62 in the vicinity of the divided frequency.

The invention of claim 1 solves such conventional problems, and can prevent excessive output from speakers, etc., and also provides excellent frequency band division in which the level does not increase in the vicinity of the division frequency when combining two outputs. The purpose is to provide equipment.

[0011] Furthermore, the invention of claim 2 provides a compressor noise reduction device that can reduce compressor noise and obtain flat frequency characteristics without the frequency characteristics depending on the threshold value of the compressor. It is to be.

0012

[Means for Solving the Problems] In order to achieve the above-mentioned object, the invention of claim 1 provides a first level control means that is connected to the input side of the first level control means provided on the output side of the low-pass filter, and has an inverse characteristic of the low-pass filter. a first filter having a first filter;
A first envelope generating means detects the output level of the filter and generates an envelope signal, and the second level control means is connected to the input side of the high pass filter output side, and is connected to the input side of the second level control means provided on the output side of the high pass filter, and is connected to the input side of the second level control means provided on the output side of the high pass filter. and a second envelope generating means that detects the level of the output signal of the second filter and generates an envelope signal, The level of this signal is detected by a first envelope generating means to generate an envelope signal, and the first level controlling means is controlled. The second envelope generating means detects the level of the output signal and generates an envelope signal to control the second level control means. .

[0013] Furthermore, in order to achieve the above object, the invention of claim 2 has a first compressor connected to the input side of the compressor control circuit provided on the output side of the pre-emphasis circuit, and having characteristics opposite to those of the pre-emphasis circuit. a de-emphasis circuit and a second de-emphasis circuit connected to the output side of the compressor, the first de-emphasis circuit weakens the level of the frequency component emphasized by the pre-emphasis circuit, and the second de-emphasis circuit weakens the level of the frequency component emphasized by the pre-emphasis circuit. The circuit is designed to reduce the output of the control circuit.

[0014]

[Operation] Therefore, according to the invention of claim 1, a compressor is provided on each output side of the low-pass filter and high-pass filter, and a low-pass filter and a high-pass filter are provided on the input side of the first and second level control means of each compressor. By inserting the first and second filters with opposite characteristics, the first and second filters correct the threshold value, so that the synthesis of the output of the frequency band division device has a level near the division frequency. It has the effect of not rising.

According to the second aspect of the invention, a compressor is provided on the output side of the pre-emphasis circuit, a first de-emphasis circuit is provided on the input side of the control circuit of the compressor, and a second de-emphasis circuit is provided on the output side of the compressor. By providing an emphasis circuit, it is possible to reduce the noise of the compressor, and the frequency characteristics do not depend on the threshold value of the compressor, resulting in the effect that a flat frequency characteristic can be obtained.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the structure of a first embodiment of the present invention. In FIG. 1, 1 is an input terminal, which is connected in parallel to the input terminal of the low-pass filter 2 and the input terminal of the high-pass filter 7.

Reference numeral 3 denotes a level control means for the compressor, and the output of the low-pass filter 2 is introduced into its input terminal. Reference numeral 4 denotes a filter having an inverse characteristic to the pre-low-pass filter 2, whose input end is connected to the output end of the low-pass filter 2.

Reference numeral 5 denotes an envelope generating means that constitutes a compressor together with the level control means 3, and this envelope generating means 5
The input terminal of the filter 4 is connected to the output terminal of the filter 4.
The level of the output signal is detected, and when the level exceeds a threshold value, an envelope signal is output to the level control means 3. 6 is a low frequency output terminal which takes out the low frequency signal output from the level control means 3 and inputs it to drive a speaker (not shown) or the like.

On the other hand, 7 is a high-pass filter that receives the signal from the input terminal 1 and outputs a high-frequency signal, and 8 is a level control means that controls the level of the high-frequency signal output from the high-pass filter 7.

Reference numeral 9 denotes a filter whose input terminal is connected to the output terminal of the high-pass filter 7 and which has characteristics opposite to that of the high-pass filter 7.
The input terminals of are connected in parallel.

Reference numeral 10 denotes an envelope generating means which constitutes a compressor together with the level control means 8 and detects the level of the output signal of the filter 9. When the envelope generating means 10 detects that the output signal of the filter 9 exceeds a threshold value, it outputs an envelope signal to the level controlling means 8. Reference numeral 11 denotes a high frequency output terminal that takes out the high frequency signal output from the level control means 8 and outputs it to a speaker or the like.

Next, the operation of the first embodiment will be explained. A signal having a flat frequency characteristic applied to the input terminal 1 in FIG. 1 is passed through a low-pass filter 2, and a signal 21 having a frequency spectrum as shown in FIG. 2 is outputted. The signal 21 is again converted into a signal having a flat frequency characteristic by a filter 4 having characteristics opposite to those of the low-pass filter 2 disposed in front.

The envelope generating means 5 uses this flat signal.
An envelope signal 22 corresponding to the threshold value is generated from , and this envelope signal 22 controls the level control means 3, so that
The level control means 3 performs an audio compression operation corresponding to the input signal.

[0024] The part related to high frequency signals operates in the same way,
An audio compression operation corresponding to the input signal is performed. That is, a signal with a flat frequency characteristic is outputted by a high-pass filter 7 as a signal having a frequency spectrum in a high frequency region, and the output signal of this high-pass filter 7 is outputted by a filter 9 having a characteristic opposite to that of the high-pass filter 7. The level of this flat signal is detected by the envelope generating means 10, and when the threshold value is exceeded, the envelope generating means 10 generates an envelope signal to determine the level. controlling the control means 8 and thus:
The level control means 8 suppresses the level of the high-frequency signal output from the high-pass filter 7, so that a high-frequency signal is obtained from the high-frequency output terminal 11, and an audio compression operation corresponding to the input signal is performed.

[0025] Thus, according to the first embodiment,
Since the envelope generating means 5 and 10 similarly operate in the passband and stopband of the low-pass filter 2 and high-pass filter 7, respectively, audio compression is performed in the stopband as well, and the frequency characteristics appearing at the output terminal are determined by the threshold value. This has the effect of matching the characteristics of the filter even for input signals exceeding .

As a second embodiment of the present invention, an amplitude limiting circuit may be provided in the filters 5 and 9 having the opposite characteristics to those of the first embodiment. In this case, if a signal having a spectrum far from the divided frequency is input, the audio compression operation can be blocked and malfunctions can be prevented.

FIG. 3 shows the configuration of a third embodiment of the present invention. In FIG. 3, 31 is an input terminal,
32 is a pre-emphasis circuit 32 whose input terminal is connected to this input terminal 31.

Reference numeral 33 is a de-emphasis circuit whose input end is connected to the output end of the pre-emphasis circuit 32, and which returns the signal whose high frequency level has been emphasized by the pre-emphasis circuit 32 to a signal having flat frequency characteristics. This is a filter having characteristics opposite to those of the emphasis circuit 32.

Reference numeral 34 has an input terminal connected to the output terminal of the de-emphasis circuit 33, detects the level of the output signal of the de-emphasis circuit 33, and when the de-emphasis circuit 33 generates an output with a flat frequency characteristic, a level control means. It is an envelope generating means that outputs to 35.

The level control means 35 inputs the output signal of the pre-emphasis circuit 32 and controls the level according to the output signal of the envelope generation means 34, and 36 connects the output end of the level control means 35 with an input end. This is a de-emphasis circuit which restores the level of the emphasized high frequency region of the output signal of the level control means 35 to the original level. Reference numeral 37 is an output terminal for taking out the output signal of the de-emphasis circuit 36 and providing it for use in a speaker drive or the like.

Next, the operation of the third embodiment will be explained. In FIG. 3, a pre-emphasis circuit 32 outputs a signal applied to an input terminal 31 in which the level of a high frequency region is increased. This signal is converted again into a signal with flat frequency characteristics by a filter having characteristics opposite to those of the pre-emphasis circuit 32, that is, a de-emphasis circuit 33.

This flat signal causes the envelope generating means 34 to generate an envelope signal, and the level controlling means 35 controls the level controlling means 35 by using this envelope signal. The level of the signal whose level has increased is suppressed and output to the de-emphasis circuit 36.

By using this de-emphasis circuit 36 to further return the level of the high frequency range of the output signal of the level control means 35 to a signal having an original flat frequency characteristic,
An audio compression operation corresponding to the input signal is performed.

[0034] The above description has been made regarding the processing of the low frequency signal system, but the portion relating to the processing of the high frequency signal system operates in the same manner, and the audio compression operation corresponding to the input signal is performed.

As described above, according to the third embodiment,
Similarly, the envelope generating means 34 is used in the level increasing range and non-level increasing range of the filter, that is, the pre-emphasis circuit 32.
operates, audio compression is performed in both the level increasing range and non-level increasing range of the filter, and in order to return the frequency characteristic to flat in the de-emphasis circuit 33 again, the frequency characteristic appearing at the output terminal 37 is It has the effect of flat operation even for input signals exceeding the threshold.

Further, the level control means 35 is inputted with a signal emphasizing the high frequency range, and in order to return the high frequency level emphasized at the output of the level control means 35 to a flat level by the de-emphasis circuit 36, the level control means 35 , even if noise occurs, the output de-emphasis circuit has the effect of reducing the noise.

Note that in the third embodiment, an AD (analog-digital) converter is inserted on the output side of the pre-emphasis circuit 32, and the de-emphasis circuit 33
A DA converter may be inserted on the output side. In this case, the noise generated in the AD converter and the DA converter is further attenuated in the high frequency range by the de-emphasis circuit 36, which has the effect of reducing the apparent rise in noise.

[0038]

[Effects of the Invention] As is clear from the above embodiment, the invention of claim 1 is equipped with a compressor on each output side of the low-pass filter and the high-pass filter, so that excessive output can be prevented, and the compressor connected after the output can be prevented. It has the advantage of protecting speakers and the like.

Furthermore, by inserting a filter having the inverse characteristic of the prefilter into the input side of the level control means of each compressor, the inverse characteristic filter corrects the threshold value, so that the output of the frequency band dividing device This has the effect that the level does not increase in the vicinity of the divided frequency.

Further, as is clear from the above embodiment, the invention of claim 2 is provided with a compressor on the output side of the pre-emphasis circuit, and has a characteristic opposite to that of the pre-emphasis circuit on the input side of the level control means of the compressor. A de-emphasis circuit is inserted to return the level of the frequency domain emphasized by the pre-emphasis circuit to the original flat frequency characteristic, the output thereof is detected by the envelope generating means, and the level control means is controlled by the envelope signal. By further flattening the output of the level control means using a de-emphasis circuit, compressor noise can be reduced, and the effect is that the frequency characteristics do not depend on the compressor's threshold and a flat frequency characteristic can be obtained. has.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram of a frequency band division device in a first embodiment of the present invention.

[Figure 2] Conceptual diagram of the operation of the device

FIG. 3 is a schematic block diagram of a compressor noise reduction device in a third embodiment of the present invention.

[Figure 4] Schematic block diagram of a conventional frequency band division device

[
Figure 5: Conceptual diagram of the operation of the device

[Figure 6] Conceptual diagram of the operation of the device

[Explanation of symbols]

1 Input terminal 2 Low-pass filter 3 Level control means 4 Low-pass filter inverse characteristic filter 5 Envelope generation means 6 Low-frequency output terminal 7 High-pass filter 8 Level control means 9 High-pass filter inverse characteristic filter 10 Envelope generation means 11 High-frequency output terminal 31 Input Terminal 32 Pre-emphasis circuit 33 De-emphasis circuit 34 Envelope generating means 35 Level control means 36 De-emphasis circuit 37 Output terminal

Claims (2)

[Claims] 1. A low-pass filter that outputs low-frequency components of an input signal; and a first filter that has characteristics opposite to the low-pass filter and returns the output signal of the low-pass filter to a signal having flat frequency characteristics. And this first
a first envelope generating means for detecting the output level of the filter and generating an envelope signal;
constitutes a first compressor together with an envelope generating means,
and a first level control means that is controlled by the envelope signal and suppresses the level of the output signal of the low-pass filter to output a low frequency signal corresponding to the input signal;
a high-pass filter that outputs high-frequency components of the input signal; a second filter that has opposite characteristics to the high-pass filter and exchanges the output signal of the high-pass filter with a signal that has the original flat frequency characteristics; a second envelope generating means that detects the output level of the second filter and generates an envelope signal; together with the second filter and the second envelope generating means, a second compressor is configured; and second level control means that is controlled by the envelope signal output from the envelope generation means and suppresses the level of the output signal of the high-pass filter to output a high frequency signal corresponding to the input signal. 2. A pre-emphasis circuit that emphasizes a predetermined frequency range of an input signal, a first de-emphasis circuit that converts the output of the pre-emphasis circuit back into a signal having an original flat frequency characteristic, and a first de-emphasis circuit that enhances a predetermined frequency range of an input signal. an envelope generating means for detecting an output signal of the de-emphasis circuit and generating an envelope signal; a compressor is configured together with the first de-emphasis circuit and the envelope generating means, and the pre-emphasis circuit is controlled by the envelope signal; A noise reduction device for a compressor, comprising: a level control means for suppressing an emphasized level of an output signal of the level control means; and a second de-emphasis circuit for suppressing the level of an output signal of the level control means.