JPH11298998A - Low frequency sound enhancing circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance clear and crisp low frequency sound and to make the efficiency of a power amplifier high in sound reproduction. SOLUTION: This low frequency sound enhancing circuit is provided with a 1st LPF 1 that extracts a low frequency sound component among a received sound signal, with a low sound leading detection control circuit 2 consisting of series connection of an amplifier 3 amplifying an output of the 1st LPF 1, a rectifier circuit 4 rectifying an amplified signal, a differentiation circuit 5 detecting a leading of a level of a rectified signal, and an integration circuit 6 that adjusts a width of a pulse outputted from the differentiation circuit 5, with a volume control amplifier 7 that adjusts an output of the 1st LPF 1, and enhances the low frequency component, only within the width of the leading pulse obtd. by the integration circuit 6, passing through the 1st LPF 1 and a 2nd LPF 8 eliminates an amplification switching noises and its output is added to the received sound signal so as to enhance the low frequency sound component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the enhancement of low-frequency range of sound reproduction. In particular, the present invention relates to bass reproduction of a TV set with poor bass reproduction.

[0002]

2. Description of the Related Art A speaker mounted on a TV set cannot reproduce a sufficient bass component due to size and shape restrictions, and digital high performance music sources such as BS (satellite broadcasting) and high definition are broadcast. Nevertheless, there was a problem that only poor bass reproduction could be enjoyed. In recent years, the number of occasions of connection with external source devices such as CDs and LDs has increased, and the need for bass reproduction has been desired.
Normally, the bass can be enhanced by boosting the bass with a tone control circuit (tone control). However, this tone control circuit is often implemented as an IC, and the dynamic range from the power supply used by the IC is usually increased. Once decided, naturally the amount of boost is limited. To compensate for this drawback, as shown in Japanese Utility Model Laid-Open No. 4-112599, a sound reproducing method for adding and amplifying only the low frequency component of a voice LR signal at a stage prior to a power amplifier and adding the result to the respective LR signals to enhance the bass. It has been known. Hereinafter, an example of bass enhancement will be described with reference to FIG.

In FIG. 4, reference numeral 20 denotes a filter block composed of an LPF for extracting a bass component and an HPF for extracting a treble component, 21 denotes an adder for adding only the bass component of the audio LR signal, and 22 denotes a signal level. An amplifier 23 amplifies the sound LR to which the amplified bass component is input.
An adder for adding the treble component of the signal, a power amplifier for amplifying the power, and a speaker 25 are provided.

The operation of the above-structured bass enhancement will be described. The input audio LR signal is separated into a low frequency component and a high frequency component by the filter block 20, and only the low frequency component is added by the adder 21. The added bass component is amplified according to the effect by the amplifier 22, added to the high tone component of the audio LR signal through the adder 23, and the audio signal of the entire band whose bass is enhanced is power-amplified by the power amplifier 24. , From the speaker 25.

[0005]

However, in the above conventional configuration, the tone control is the same as the bass enhancement, and if the boost amount of the tone control is increased,
This is a method that can be solved, and measures for power supply to the IC and a method of expanding the dynamic range may be considered. However, although there is an effect of enhancing bass, the load on the power amplifier increases in each case. That is, the bass signal applied to the power amplifier becomes large, and a heat generation problem of the power amplifier occurs. T
The power amplifier used in the V set has only an output of about 10 W, and there is a concern that the power amplifier may be damaged by heat. In addition, since the bass is constantly boosted, there is a problem that the bass becomes a rough low tone, the sound becomes muffled, and the sound becomes indistinct and hard to hear.

[0006]

In order to solve the above problems, the bass enhancement circuit according to the present invention enhances the bass signal level only at the rising portion of the bass and reproduces the signal, thereby achieving good separation and low power. This is characterized in that the bass is enhanced.

According to the present invention, it is necessary to effectively use the psychological effect due to the feeling of attack of the bass, to enhance the level of only the rising part of the bass, to reproduce the clear bass in an enhanced manner, and to enhance the bass all the time. Since it is no longer necessary, a bass enhancement circuit that can reduce the load on the power amplifier can be provided.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A bass enhancement circuit according to a first aspect of the present invention extracts a bass component from an input audio signal, and enhances and reproduces a bass signal level only in a rising portion of the bass. This makes it possible to realize bass enhancement that requires good power and requires low power.

Next, a bass enhancement circuit according to a second aspect of the present invention provides a first LPF for extracting a bass component from an input audio signal, and amplifies the first LPF output signal. A low-pitched sound rise which is connected in series with a rectifier circuit for rectifying a signal level at a stage subsequent to the amplifier, a differentiating circuit for detecting a rising of the rectified signal level, and an integrating circuit for adjusting a pulse width output by the differentiating circuit. A detection control circuit, and a volume control amplifier for adjusting a level of the first LPF output signal;
The bass component that has passed through the first LPF is boosted only in the pulse width section of the rising portion of the bass obtained by the rising detection control circuit, and a boost section of the boost section is provided after the volume control amplifier (hereinafter abbreviated as VCA). A second LPF for removing noise generated at the time of release;
The low frequency component passed through the LPF and the input audio signal are added to realize low frequency enhancement.

Next, a bass enhancement circuit according to a third aspect of the present invention, in the bass enhancement circuit according to the first aspect, is provided after the adder for adding the input audio LR signal. First to extract the bass component from the audio signal
LPF, a rectifier circuit for rectifying a signal level after the amplifier for amplifying the first LPF output signal, a differentiating circuit for detecting a rise of the rectified signal level, and a pulse width output from the differentiating circuit And a volume control amplifier for adjusting the level of the first LPF output signal.
The bass component that has passed through the PF is enhanced only in the pulse width section of the rising portion of the bass obtained by the rising detection control circuit, and the noise generated when the enhancement section is released is removed downstream of the volume control amplifier. LPF
And adds the bass component that has passed through the second LPF to the input audio LR signal, thereby realizing bass enhancement with the two-channel audio LR signal.

An embodiment of the present invention will be described below with reference to FIGS. (Embodiment 1) Embodiments of the invention described in claims 1 and 2 of the present invention will be described below with reference to FIGS.
This will be described with reference to FIG.

FIG. 1 is a block diagram of a bass enhancement circuit according to an embodiment of the present invention. In FIG. 1, 1 is a first LPF for extracting a bass component, 2 is a bass rise detection control circuit, 3 is an amplifier for amplifying the signal level extracted by the first LPF, and 4 is rectifying the signal level. Rectifying circuit, 5 is a differentiating circuit for detecting the rise of the rectified signal level, 6 is an integrating circuit for adjusting the pulse width output from the differentiating circuit, and 7 is a low-frequency component extracted by the first LPF. The VCA 8 for adjusting the signal level is a second LPF 9 for removing noise generated when the enhancement section is released from the low frequency components obtained by the VCA, and the second LPF 9 is for adding an input audio signal and a low frequency part to be enhanced. It is an adder.

The operation of the bass enhancement circuit configured as described above will be described. The input audio signal is the first
The LPF 1 extracts only the low frequency component, and the signal is amplified by the amplifier 3. The amplified bass component is rectified by the rectifier circuit 4 and its envelope level is output.
Next, in order to detect the rising of the envelope, it is differentiated by the differentiating circuit 5 to generate a rising pulse. In order to extend this rising pulse width appropriately according to the effect,
An integrating circuit 6 is used. Only when this pulse is at the H level, the level of the bass component extracted by the first LPF 1 is increased by the VCA 7 and only the bass component is extracted by the second LPF 8 using an appropriately time-expanded pulse. After doing
The adder 9 adds the input audio signal to the input audio signal, thereby increasing the signal level of only the rising part of the low frequency component. This will be specifically described as follows.

Normally, a bass is a typical musical instrument for reproducing bass, and it is assumed that the bass is played with a bonbon (referred to as bass running). In this case, one tone of the bass has a waveform of several cycles, there is a blank, and the next tone comes again several cycles. That is, it is the intention of the present invention to increase the signal level by several rising cycles of the waveform of several cycles of one bass sound to enhance the attack feeling.

FIG. 2 shows a time series waveform of each part of the bass enhancement circuit shown in FIG. 1, and is an explanatory diagram when a sine wave is input. That is, when the input audio signal is a low tone only and a waveform (a) is input, the output of the amplifier 3 has a clipped waveform shown in (b). The clipped audio waveform is integrated by the rectifier circuit 4 as shown in (c), and an envelope signal can be extracted. That is, a signal presence / absence section is determined. When this is differentiated by the differentiating circuit 5, a waveform (d) is obtained. (D) The waveform is for detecting a rising portion of a signal from no signal and has a narrow pulse width.
The time width τ is set to a time width in which the effect is obtained by the integration circuit 6, and (e) a waveform is obtained. According to experiments, a time width τ of about several hundred ms is sufficient. Only in the H section of the integrating circuit 6, the low-frequency component is level-amplified by the VCA to obtain a waveform (f). (F) The release time of the waveform is determined by the time constant τ of the integrating circuit 6, and depending on the timing,
It becomes discontinuous and harmonic noise is generated at the time of release. In order to remove the amplification release noise, the second LPF 8 deletes the harmonic component of the waveform, thereby obtaining a waveform (g). By adding this (g) waveform to the input signal, the (h) signal waveform is finally output. As described above, by increasing the signal level of the bass sound only in the rising portion of the bass component, it is possible to enhance the bass sound with a clear and attacking feeling. (Embodiment 2) Next, an embodiment of the invention described in claim 3 of the present invention will be described with reference to FIG.
The same components as those in the above-described embodiment are denoted by the same reference numerals, and description thereof is omitted.

FIG. 3 is a block diagram showing a bass enhancement circuit according to an embodiment of the present invention. In FIG. 3, reference numeral 10 denotes an adder for adding a voice LR signal, 1 denotes a first LPF for extracting a bass component, 2 denotes a bass onset detection control circuit, and 3 denotes a signal level extracted by the first LPF. , A rectifier circuit for rectifying the signal level,
Is a differentiation circuit that detects the rise of the rectified level,
6 is an integrating circuit for adjusting the pulse width output from the differentiating circuit, 7 is a VCA for adjusting the signal level of the bass component extracted by the first LPF, and 8 is a bass component obtained from the VCA. , A second LPF 9 for removing noise generated when the enhancement section is released is an adder for adding the input audio signal and the bass component to the LR, respectively.

The operation of the bass enhancement circuit configured as described above will be described. The input signal of the audio LR2 channel is added by the adder 10. Normally, the bass component is an LR in-phase signal at the time of two channels, and thus can be added. From the added signal, through the first LPF 1 that extracts a bass component, a rising portion of the bass is detected in the same configuration as in the first embodiment, and the VCA 7 passes the bass component only at the rising portion. The noise is removed by the LPF 8 and the addition is performed on the LR inputted by the adder 9, thereby simplifying the circuit and enhancing the same bass.

In the first and second embodiments, the low tone component level control is performed only on the rising part of the low tone by the VCA 7, but it can be easily realized by a simple electronic switch and a mute circuit using a transistor. Needless to say, the amount of bass addition also needs to be adjusted.

[0019]

As described above, the bass enhancement circuit of the present invention enhances and reproduces the bass signal level only at the rising portion of the bass, thereby reproducing a sharp low-pitched bass. Since no bass enhancement is performed for the entire time, it is possible to provide a bass enhancement circuit that can reduce the load on the power amplifier and minimize heat generation.

If the response of the speaker is poor,
Although the rising waveform becomes dull and the bass tone becomes poor, if the dulling of the rising waveform is complemented in advance by the bass enhancement circuit of the present invention, bass reproduction by a speaker that is faithful to the original sound waveform can be made.

[Brief description of the drawings]

FIG. 1 is a block diagram of a bass enhancement circuit according to a first embodiment of the present invention.

FIG. 2 is a waveform chart for explaining the operation of each unit in FIG. 1;

FIG. 3 is a block diagram of a bass enhancement circuit according to a second embodiment of the present invention.

FIG. 4 is a block diagram of a conventional bass enhancement circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 LPF 2 Bass rise detection control circuit 3 Amplifier 4 Rectifier circuit 5 Differentiator circuit 6 Integrator circuit 7 Volume control amplifier (VCA) 8 LPF 9 Adder 10 Adder

Claims (3)

[Claims] A low tone component is extracted from an input audio signal, and a low tone signal level at only a rising part of the low tone is enhanced to be reproduced, so that a low tone can be enhanced with good separation and low power. A bass enhancement circuit characterized by the following. 2. A rectifying circuit for rectifying a signal level at a stage subsequent to an amplifier for amplifying the first LPF output signal, a first LPF for extracting a bass component from the input audio signal, and A low-frequency rise detection control circuit in which a differentiation circuit for detecting the rise of the signal level and an integration circuit for adjusting the pulse width output from the differentiation circuit are connected in series, and the first LPF output signal is Equipped with a volume control amplifier to adjust the level,
The bass component that has passed through the first LPF is enhanced only in the pulse width section of the rising portion of the bass obtained by the rising detection control circuit, and the noise generated when the enhancement section is released is provided downstream of the volume control amplifier. A bass enhancement circuit comprising a second LPF to be deleted, wherein a bass component passing through the second LPF is added to an input audio signal to enhance bass. 3. A first LPF for extracting a bass component of the input audio signal, and an amplifier for amplifying the first LPF output signal, after the adder for adding the input audio LR signal. A rectifier circuit that rectifies the signal level at the subsequent stage,
A low-pitched sound rise detection control circuit in which a differential circuit for detecting the rise of the rectified signal level and an integrator circuit for adjusting the pulse width output from the differential circuit are connected in series; A volume control amplifier for adjusting a level of an output signal, wherein a bass component having passed through the first LPF is enhanced only in a pulse width section of a rising portion of a bass obtained by the rising detection control circuit; In the subsequent stage, a second step is performed to remove noise generated when the enhancement section is released.
A bass enhancement circuit for adding bass components passed through the second LPF to the input audio LR signal to enhance bass.