JP2002185278A - Sound quality control circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sound quality control circuit constructed by using a digital signal processor with which characteristics without unnatural acoustic feeling can be obtained with a simple structure. SOLUTION: The circuit is provided with a primary digital filter 1 and a secondary digital filter 2, and the primary and secondary filters 1, 2 are arranged so as to be connected in series. That is, bass and treble functions can be realized by a combination of the filters inside the digital signal processor, which has been realized in a conventional sound quality control circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound quality control circuit used for a plasma display device, a television receiver, a stereo, and the like.

[0002]

2. Description of the Related Art Conventionally, in a sound quality control circuit of this kind, a circuit for emphasizing or weakening a bass (low frequency range) or treble (high frequency range) or the like with respect to an input audio signal, a surround circuit, and the like are realized. It is configured by combining integrated circuits and the like.

Further, when such a configuration is configured by an analog circuit, there is a problem that the number of parts is increased and the circuit scale is increased. To solve this problem, a digital signal processor (hereinafter referred to as DSP) has recently been used. A sound quality control circuit has been configured with a circuit using the same.

[0004]

However, when a sound quality control circuit is constituted by such a DSP, a circuit for controlling the bass (low range) and treble (high range) is constituted by a simple digital filter. For example, the treble characteristic has a small change from the middle range to the high range where the perceived change is felt, so that the characteristic realized by the conventional sound quality control circuit cannot be obtained, and it is intended to change this characteristic from a slightly lower frequency. However, there is a problem that the coefficient of the digital filter overflows and the filter cannot be formed.

Therefore, in a conventional sound quality control circuit using a DSP, when an attempt is made to realize a function of emphasizing or weakening a bass (low frequency range) or a treble (high frequency range), an auditory sense is increased.
There was a problem that the effect was not felt much.

[0006] The present invention solves such a problem, and a sound quality control circuit configured using a DSP includes:
It is an object of the present invention to obtain a characteristic that does not give a sense of incompatibility with a simple configuration.

[0007]

To solve this problem, a sound quality control circuit according to the present invention comprises a primary digital filter and a secondary digital filter, and connects the primary and secondary digital filters in series. It is what was arranged. That is, by combining filters inside the DSP, the bass and treble functions realized by the conventional sound quality control circuit can be realized.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention includes a primary digital filter and a secondary digital filter, and the primary and secondary digital filters are connected in series and arranged. It was done.

Further, the invention according to claim 2 of the present invention provides:
The secondary digital filter is a bell-shaped filter and its center frequency is set near the cut-off frequency of the primary digital filter. It achieves the characteristics of the bass and treble functions that were conventionally realized while using a DSP. In addition, there is an effect that a characteristic that does not cause uncomfortable feeling can be obtained.

[0010] Further, the invention according to claim 3 of the present invention provides:
It is configured so that a secondary digital filter can be turned on / off. According to this configuration, for example, in the case of an input signal including a relatively wide band frequency component such as music, if the secondary digital filter is turned off, only the low and high frequencies are emphasized or weakened. It is possible,
When the input signal has a relatively narrow band centered on a human voice, such as narration, turning on the secondary digital filter enables the low- and mid-high frequencies even in the human voice. It has the effect of emphasizing or weakening, realizing the characteristics of the bass and treble functions that have been conventionally realized in terms of audibility, and obtaining the desired sound quality.

A sound quality control circuit according to an embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a block diagram showing a treble circuit of a sound quality control circuit according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a primary digital filter, reference numeral 2 denotes a secondary digital filter, and the secondary digital filter. The digital filter 2 is connected in series before the primary digital filter 1. In addition, these digital filters 1,
As long as 2 is connected in series, it may be in the former stage or the latter stage.

The digital filters 1, 2
Are generally known as adders 3, 4, delay units 5, 6, 7, 8, 9 and multipliers 10, 11, 12, 1,
3, 14, 15, 16, and 17.

The operation of the sound quality control circuit configured as described above will be described below. Taking the treble characteristic as an example, a high-pass filter (hereinafter referred to as HPF) is constituted by the primary digital filter 1. In the example, the cutoff frequency is 5 KHz. The characteristics are shown in FIG.

Then, the next secondary digital filter 2
Constitute a bell-shaped filter. The center frequency is set near the cut-off frequency of the primary digital filter 1. In the example, it is set to 5 KHz. The characteristics are shown in FIG. By connecting these primary digital filters 1 and secondary digital filters 2 in series, the characteristics shown in FIG. 4 are obtained.

As described above, the filter composed of the secondary digital filter 2 raises the treble characteristic from the middle frequency range to the high frequency range, and the conventional treble characteristic cannot be obtained by the primary digital filter 1 alone. Almost the same characteristics can be obtained.

Here, according to the circuit configuration according to the embodiment of the present invention, when the input signal is a relatively wide band signal such as music, the characteristics of the secondary digital filter 2 are changed over the entire range. By using the pass characteristic, the total characteristic becomes a characteristic as shown in FIG. 2 when the treble characteristic is taken as an example, and when the input signal is mainly a human voice such as a narration, a secondary digital signal is obtained. If the characteristic of the filter 2 is a bell-shaped filter and its center frequency is set near the cutoff frequency of the primary digital filter 1, the total characteristic will be as shown in FIG.

That is, by configuring the secondary digital filter 2 so as to be able to be turned on / off, when the input signal contains a relatively wide band frequency component such as music, for example, By turning off the secondary digital filter, only the low and high frequencies can be emphasized or weakened.If the input signal has a relatively narrow band centered on human voice, such as narration, the secondary digital filter By turning on, even in the case of human voice, the mid-low range and mid-high range are emphasized or weakened, and the characteristics of the bass and treble function that were conventionally realized in terms of hearing are realized, and the desired sound quality is obtained The effect of being able to obtain is obtained.

[0019]

As described above, according to the present invention, since the primary digital filter and the secondary digital filter are connected in series, if the treble characteristic is taken as an example, the secondary digital filter is used. Can correct the characteristics from the middle range to the high range, so that the same treble characteristics as those of the related art can be obtained.
To achieve the same characteristics of bass and treble function as before while using, and to obtain the characteristics without discomfort that the effect (change) on the perception is not felt even if the bass and treble are changed, and the desired sound quality Can be.

If the characteristics of the secondary digital filter are all-pass characteristics, in the case of an input having a wideband signal component, such as music, only the high and low frequencies are changed, The effect is that high-frequency and low-frequency characteristics in which loss is likely to occur in the speaker and the speaker can be corrected.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a sound quality control circuit according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram of a primary digital filter of the circuit.

FIG. 3 is a characteristic diagram of a secondary digital filter of the circuit.

FIG. 4 is a total characteristic diagram of the sound quality control circuit of the present invention.

[Explanation of symbols]

 1 Primary digital filter 2 Secondary digital filter

Claims (3)

[Claims] 1. A sound quality control circuit comprising a primary digital filter and a secondary digital filter, wherein the primary and secondary digital filters are connected in series and arranged. 2. The sound quality control circuit according to claim 1, wherein the secondary digital filter is a bell-shaped filter, and a center frequency thereof is set near a cutoff frequency of the primary digital filter. 3. The sound quality control circuit according to claim 1, wherein a secondary digital filter can be turned on / off.