JP3799813B2 - Bass enhancement circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to low sound range enhancement for audio reproduction. In particular, the present invention relates to bass reproduction of a TV set with poor bass reproduction.
[0002]
[Prior art]
Speakers installed in TV sets cannot reproduce sufficient bass components due to size and shape restrictions, and digital high performance music sources such as BS (Satellite Broadcasting) and Hi-Vision are being broadcast. There was a problem that only poor bass reproduction could be enjoyed. Recently, there have been increased opportunities to connect to external source devices such as CDs and LDs, and the need for low-frequency reproduction has been desired. Usually, in order to enhance the bass, it is only necessary to boost the bass with a sound quality control circuit (tone control). Usually, this sound quality control circuit is often integrated into an IC, and the dynamic range is controlled by the power supply used by the IC. Naturally, the amount of boosting is limited. In order to compensate for this drawback, as shown in Japanese Utility Model Laid-Open No. 4-112599, an audio reproduction method for enhancing the low frequency by adding and amplifying only the low frequency component of the audio LR signal at the front stage of the power amplifier and adding the amplified component to the LR signal. It has been known. Hereinafter, an example of bass enhancement will be described with reference to FIG.
[0003]
In FIG. 4, reference numeral 20 is a filter block comprising an LPF for extracting a low frequency component and an HPF for extracting a high frequency component, 21 is an adder for adding only the low frequency component of the audio LR signal, and 22 is for amplifying the signal level. An amplifier 23 is an adder that adds the amplified bass component to the treble component of the input audio LR signal, 24 is a power amplifier that amplifies power, and 25 is a speaker.
[0004]
The operation of the bass enhancement configured as described above 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 by the amplifier 22 according to the effect, and added through the adder 23 with the treble component of the audio LR signal, and the audio signal of the entire band with the enhanced bass is amplified by the power amplifier 24. And reproduced from the speaker 25.
[0005]
[Problems to be solved by the invention]
However, the above-described conventional configuration is the same as the tone control bass enhancement, and can be solved by increasing the tone control boost amount, and an IC power supply countermeasure and a dynamic range expansion method may be considered. However, although there is an effect of enhancing the bass, any of them increases the burden on the power amplifier. That is, the bass signal applied to the power amplifier becomes large, and the power amplifier generates heat. The power amplifier used in the TV set has only an output of about 10 W, and there is a concern about destruction due to heat. In addition, since the bass is always boosted, there is a problem that the sound becomes a voluminous bass, and on the contrary, it becomes a muffled sound, which makes it difficult to hear without clarity.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the bass enhancement circuit of the present invention is characterized in that the bass signal level of only the rising part of the bass is enhanced and reproduced, thereby improving the bass tone that is good at breaking and requires low power. all SANYO was, also, in which so as to achieve bass enhancement by removing noise generated in enhancing the bass signal level of the rising portion of the bass.
[0007]
According to the present invention, the psychological effect due to the attack feeling of the bass is effectively used, the level of only the rising part of the bass is enhanced, and the low-pitched bass is enhanced and reproduced, and it is not necessary to enhance the bass all the time. burden on the power amplifier can also be reduced, and, as it can provide the bass enhancement circuit to be able to achieve bass enhancement by removing noise in enhancing the bass signal level of the rising portion of the bass There is .
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The bass enhancement circuit of the present invention is characterized by extracting a bass component from an input audio signal and enhancing and reproducing the bass signal level of only the rising part of the bass . Noise at the time of enhancing the bass signal level is removed to enhance the bass , and it is possible to realize bass enhancement that is good in terms of tearing and requires low power.
[0009]
First, the bass enhancement circuit according to claim 1 of the present invention, among the input audio signal, a first LPF for extracting a bass component, downstream of the amplifier for amplifying the first LPF output signal A bass rise detection control circuit comprising a rectifier circuit that rectifies a signal level, a differentiation circuit that detects a rise of the rectified signal level, and an integration circuit that adjusts a pulse width output from the differentiation circuit. And a volume control amplifier that adjusts the level of the first LPF output signal, and a low-frequency component that has passed through the first LPF is converted into a pulse width of a rising portion of a low-frequency sound obtained by the rising-edge detection control circuit. A second LPF that enhances only the section and deletes noise generated when the enhancing section is released after the volume control amplifier (hereinafter abbreviated as VCA). Can be achieved by including a bass component having passed through the second LPF, it adds the input audio signal, to remove to the bass enhancing noise in enhancing the bass signal level of the rising portion of the bass It is possible to realize bass enhancement.
[0010]
Also, bass enhancement circuit according to claim 2 of the present invention, the bass enhancement circuit of claim 1, downstream of the adder that adds the input audio LR signal, the input audio signal A first LPF that extracts a bass component, a rectifier that rectifies the signal level downstream of an amplifier that amplifies the first LPF output signal, a differentiation circuit that detects the rise of the rectified signal level, A bass rising detection control circuit in which an integration circuit for adjusting the pulse width output from the differentiation circuit is connected in series, and a volume control amplifier for adjusting the level of the first LPF output signal, The volume control is performed by enhancing the bass component that has passed through the first LPF only in the pulse width section of the rising portion of the bass obtained by the rising detection control circuit. Downstream of the pump, comprising a second LPF to remove the noise generated at the time of release of the enhancement section, wherein the bass component that has passed through the second LPF, respectively added to the input audio LR signal, the rise of bass It is possible to realize bass enhancement by removing noise when enhancing the bass signal level of the part with a two-channel signal of the voice LR.
[0011]
Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 3.
(Embodiment 1)
Hereinafter, an embodiment of the present invention described in claim 1 of the present invention will be described with reference to FIGS.
[0012]
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 that extracts a bass component, 2 is a bass rising detection control circuit, 3 is an amplifier that amplifies the signal level extracted by the first LPF, and 4 is a rectifier for the signal level. A rectifier circuit 5 for detecting a rising edge of the rectified signal level, 6 an integrator circuit for adjusting a pulse width output by the differentiator circuit, and 7 for a bass component extracted by the first LPF. VCA that adjusts the signal level, 8 is a second LPF that deletes noise generated when the enhancement section is released, among the bass components obtained by the VCA, and 9 is an input voice signal and a bass part that is enhanced It is an adder.
[0013]
The operation of the bass enhancement circuit configured as described above will be described. From the input audio signal, only the low sound component is extracted by the first LPF 1, and the signal is amplified by the amplifier 3. The amplified bass component is rectified by the rectifier circuit 4 and the envelope level is output. Next, in order to detect the rising edge of the envelope, differentiation is performed by the differentiating circuit 5 to generate a rising pulse. An integrating circuit 6 is used to appropriately extend the rising pulse width according to the effect. Using an appropriately time-extended pulse, only when this pulse is at the H level, the bass component extracted by the first LPF 1 is increased in level by the VCA 7 and only the bass component is extracted by the second LPF 8. After that, the adder 9 adds the input audio signal to increase the signal level of only the rising portion of the bass component. Specifically, it is as follows.
[0014]
Usually, the bass is a representative instrument for playing bass, and the case where the bass is played with a bonbon (referred to as bass running) is considered. In this case, a waveform of several cycles appears for one note of the bass, there is a blank, and the next note also comes for several cycles. That is, the intent of the present invention is to increase the signal level and strengthen the sense of attack by the rising cycle of several waveforms of one bass tone.
[0015]
FIG. 2 shows time-series waveforms 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 only a low tone and (a) a waveform is input, the output of the amplifier 3 becomes a clipped waveform shown in (b). The clipped sound waveform is integrated by the rectifier circuit 4 as shown in (c), and the envelope signal can be taken out. That is, the signal presence / absence section is determined. When this is differentiated by the differentiation circuit 5, (d) waveform is obtained. (D) The waveform detects a rising portion of a signal from no signal and has a narrow pulse width. A time width τ is set as a time width in which the effect is obtained by the integrating circuit 6, and (e) a waveform is obtained. According to the experiment, a time width τ of about several hundreds ms is sufficient. Only in the H section of the integration circuit 6, the bass component is level amplified by VCA to obtain (f) waveform. (F) The release time of the waveform is determined by the time constant τ of the integration circuit 6 and is discontinuous depending on the timing, and harmonic noise is generated at the time of release. In order to remove this amplification cancellation noise, the second LPF 8 deletes the harmonic component of the waveform (g) to form a waveform. By adding (g) the waveform and the input signal, (h) the signal waveform is finally output. In this way, by increasing the bass signal level only at the rising portion of the bass component, it is possible to enhance the bass with a good attack feeling.
(Embodiment 2)
Next, an embodiment of the invention described in claim 3 of the present invention will be described with reference to FIG. In addition, about the same structure as embodiment mentioned above, the same code | symbol is used and description is abbreviate | omitted.
[0016]
FIG. 3 is a block diagram of a bass enhancement circuit in one embodiment of the present invention. In FIG. 3, 10 is an adder for adding an audio LR signal, 1 is a first LPF for extracting a bass component, 2 is a bass rising detection control circuit, and 3 is a signal level extracted by the first LPF. 4 is a rectifier circuit that rectifies the signal level, 5 is a differentiation circuit that detects the rising of the rectified level, 6 is an integration circuit that adjusts the pulse width output by the differentiation circuit, and 7 is the first circuit. VCA for adjusting the signal level of the low frequency component extracted by the LPF of 1 and 8 for the low frequency component obtained by the VCA, the second LPF for deleting the noise generated when the enhancement section is released, 9 is input This is an adder that adds the audio signal and the bass component to the LR.
[0017]
The operation of the bass enhancement circuit configured as described above will be described. The input audio LR2 channel signals are added by the adder 10. Usually, the bass component is an LR in-phase signal in the case of 2 channels, so it can be added. Through the first LPF 1 that extracts the bass component of the added signal, the rising portion of the bass is detected with the same configuration as that of the first embodiment, and the VCA 7 passes the bass component only at the rising portion, The noise is eliminated by the LPF 8 of No. 2 and added to the LR input by the adder 9, so that the circuit can be simplified and the same bass enhancement can be achieved.
[0018]
In the first and second embodiments, only the rising part of the bass is controlled by the VCA 7 in the first and second embodiments. However, it can be easily realized by a simple electronic switch and a mute circuit using a transistor, and the bass is added depending on the effect. Needless to say, it is also necessary to adjust the amount.
[0019]
【The invention's effect】
As described above, the bass enhancement circuit according to the present invention reproduces the bass signal with a sharp edge by enhancing and reproducing the bass signal level only at the rising portion of the bass, and further, the bass enhancement for all time. Therefore, it is possible to reduce the burden on the power amplifier, suppress the generation of heat as much as possible, and remove the noise when enhancing the bass signal level at the rising part of the bass to enhance the bass. An enhancement circuit can be provided.
[0020]
In addition, when the response of the speaker is poor, the rising waveform is distorted and the low-frequency sound is worsened. Low sound reproduction by a speaker is possible.
[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 diagram for explaining the operation of each part of FIG. 1. FIG. Block diagram [Fig. 4] Block diagram of a conventional bass enhancement circuit [Explanation of symbols]
1 LPF
2 Bass rising detection control circuit 3 Amplifier 4 Rectifier circuit 5 Differentiation circuit 6 Integration circuit 7 Volume control amplifier (VCA)
8 LPF
9 Adder 10 Adder

Claims (2)

Of the input audio signal, a first LPF that extracts a bass component, a rectifier circuit that rectifies the signal level after the amplifier that amplifies the first LPF output signal, and a rise of the rectified signal level. A volume control for adjusting a level of the first LPF output signal, comprising: a differentiating circuit for detecting; and a bass rising detection control circuit in which an integrating circuit for adjusting a pulse width output from the differentiating circuit is connected in series. An amplifier is provided, and the bass component that has passed through the first LPF is enhanced only in the pulse width section of the rising part of the bass obtained by the rising detection control circuit, and the enhancement section is released after the volume control amplifier. A second LPF that eliminates noise generated from time to time, and a bass component that has passed through the second LPF and an input audio signal Calculated, and the bass enhancement circuit, characterized in that by removing noise in enhancing the bass signal level of the rising portion of the bass so achieve bass enhancement. A signal level is added to the subsequent stage of the adder for adding the input audio LR signal, and to the subsequent stage of the first LPF for extracting the low frequency component of the input audio signal and the amplifier for amplifying the first LPF output signal. A bass rise detection control circuit comprising a series connection of a rectifier circuit that rectifies the signal, a differentiation circuit that detects the rise of the rectified signal level, and an integration circuit that adjusts the pulse width output from the differentiation circuit. In addition, a volume control amplifier for adjusting the level of the first LPF output signal is provided, and the bass component that has passed through the first LPF is subjected to only the pulse width section of the rising portion of the bass obtained by the rising detection control circuit. A second LPF that removes noise generated when the enhancement section is released is provided after the volume control amplifier; Bass bass component passed through the F, respectively added to the input audio LR signal, characterized in that by removing noise in enhancing the bass signal level of the rising portion of the bass so achieve bass enhancement Enhancement circuit.

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