JP2000341798A - Device for expanding stereophonic sound image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the amplitude ratio of right and left channels from being changed and to remove a feeling of uncomfortableness that the amplitude ratio is emphasized even in the case of a low band signal (e.g. the sound of a bass or a bass drum) obtained only by panning the right and left channels at the same phase or a small phase difference. SOLUTION: The device is provided with a 1st operation part 1 for generating a difference signal SD by subtracting a 2nd input signal Rin from a 1st input signal Lin, a filter part 7 for generating a filter difference signal SF3 by filtering the difference signal SD, a 2nd operation part 2 for generating a 1st output signal Lout by adding the 1st input signal Lin to the filter difference signal SF3 outputted from the filter part 7, a 3rd operation part 3 for subtracting the signal SF3 from the filter part 7 from the 2nd input signal Rin. The filter part 7 has a low pass filter having 5 kHz cut-off frequency and a high pass filter having 200 Hz cut-off frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for enlarging and controlling a stereo sound image applied to, for example, electronic equipment, game machines, audio equipment and the like.

[0002]

2. Description of the Related Art A conventional technique is described in Japanese Patent Application Laid-Open No. 9-168200.

This device has a first operation unit for subtracting a second input signal from a first input signal to generate a difference signal, and a filter for filtering the difference signal from the first operation unit. A filter unit for generating a signal, a second arithmetic unit for adding the first input signal and a filter difference signal from the filter unit to generate a first output signal, And a third operation signal for subtracting a filter difference signal from the filter unit, wherein the filter unit includes a low-pass filter.

Japanese Patent Publication No. Hei 8-509104 describes that the filter section is constituted by a band-pass filter.

[0005]

However, if the filter section is composed of only a low-pass filter,
In the case of a stereo sound source in which extremely low-frequency sounds such as the bass sound of a musical instrument or the sound of a bass drum in a song are recorded only by panning, a low-frequency difference signal is added to and subtracted from both channels. Although the band signal is easier for the listener to perceive, the sound volume is increased, and the panning is further strengthened, resulting in a biased state. As a result, there is a problem that the tone color has a very strange feeling.

In particular, an increase in the volume of the low frequency band is a fatal problem in reproduction using a small speaker that cannot reproduce the low frequency band.

[0007] Further, in the case where the filter section is constituted by a band-pass filter, the disclosed band is as narrow as 300 Hz to 2 kHz, so that a natural maximum voice cannot be obtained.

The present invention has been made to solve such a problem.

[0009]

A stereo sound image enlarging apparatus according to the present invention includes a first operation section for subtracting a second input signal from a first input signal to generate a difference signal, and the first operation section. A filter section for filtering a difference signal from the section to generate a filter difference signal; and a second section for adding the first input signal and the filter difference signal from the filter section to generate a first output signal. An arithmetic unit, and a third arithmetic signal for subtracting a filter difference signal from the filter unit from a second input signal, wherein the filter unit includes a low-pass filter having a cutoff frequency of 5 kHz and a cutoff frequency of 5 kHz. And a high-pass filter of 200 Hz.

[0010] The filter section may further include a gain adjustment period for adjusting a fluctuation range from 0 to 1.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the stereo sound image enlarging apparatus of the present invention will be described below in detail with reference to the drawings. In FIG. 1, 1 is an external device such as a game device or an audio device, 2 is a stereo sound image enlarging device of the present invention, and 3 is a speaker. The speaker 3 has a left speaker 3a and a right speaker 3b. Left channel input signal Lin and right channel input signal Rin generated by external device 1
Is output to the stereo sound image enlargement device 2, which processes the input signals Lin and Rin and outputs the processed signals to the speaker 3.

In FIG. 2, an external input signal Lin for the left channel is supplied to a first operation unit 3 and a second operation unit 4.
Supplied to Further, an external right channel input signal Rin is supplied to the first arithmetic unit 4 and the third arithmetic unit 6.

The externally connected devices include an electronic musical instrument, a game machine, and an audio device having output terminals for the left channel signal and the right channel signal.

The first arithmetic unit 4 generates a difference signal SD by subtracting the right channel input signal Rin from the left channel input signal Lin. This first calculation unit 4 is, for example,
If the input signal Lin for the left channel is an analog signal, it is an operational amplifier, and if it is a digital signal, it is a DSP.
Alternatively, it can be configured by a subtraction process by the CPU.
The difference signal SD output from the first calculation unit 4 is supplied to the filter unit 7.

As shown in FIG. 2, the filter section 7 removes the high frequency component of the difference signal SD from the first arithmetic section 4 by setting the cutoff frequency to 20 kHz, and outputs a first filter output signal SF1. A low-pass filter 8, a high-pass filter 9 for removing a low-frequency component of the first filter output signal SF1 from the low-pass filter 8 with a cutoff frequency of 200 Hz, and outputting a second filter output signal SF2, and a second filter And an amplitude adjuster 10 for multiplying the output signal SF2 by a predetermined multiplication coefficient in order to output the filter difference signal SF3 while limiting the amplitude of the output signal SF2.

The difference signal SD input to the filter unit 7
Is an analog signal, a well-known analog low-pass filter can be used as the filter unit 7. When the difference signal SD is a digital signal, a digital filter including a delay element, a coefficient multiplier, and an adder can be used as the filter unit 7. Furthermore,
When the difference signal SD is a digital signal, the functions of the delay element, the coefficient multiplier and the adder can be realized by the processing of the DSP or the CPU. As the filter unit 7, for example, a primary IIR digital low-pass filter having a cutoff frequency of 5 kHz or a primary IIR digital highpass filter having a cutoff frequency of 200 Hz can be used.

FIG. 4 shows a combined filter characteristic of the low-pass filter 8 and the high-pass filter 9.

When the second filter output signal SF2 is an analog signal, the amplitude adjuster 10 of the filter section 7 can be adjusted by a resistor or the like. In the case of a digital signal, the multiplication function can be realized by processing of a DSP or CPU. As the multiplication coefficient of the amplitude adjuster 10, for example, a value from 0 to 1 can be used.

In the operation of this configuration, first, an input signal Lin for the left channel and an input signal Rin for the right channel are input from an external device such as a game machine. The input left-channel input signal Lin is input to the first calculation unit 4 and the second calculation unit 2. Further, the input right channel input signal Rin is input to the first arithmetic unit 4 and the third arithmetic unit 6.

First, in the first arithmetic unit, the input signal for the left channel Lin and the input signal for the right channel Ri are inputted.
Subtract n. As a result of the operation, the first operation unit 4 outputs a difference signal SD.

The difference signal SD output from the first arithmetic unit 4 is input to the subsequent filter unit 7. Filter unit 7
First, the difference signal SD is first filtered by the low-pass filter 8, and as a result, a first filter output signal SF1 is output. Next, the first filter output signal SF1 is input to the high-pass filter 9 for filtering, and the second
Is output. Finally, the second filter output signal SF2 is input to the amplitude adjuster 10, and the amplitude of the second filter output signal SF2 is multiplied by a predetermined coefficient.
Limit the amplitude. As a result of limiting the amplitude, the amplitude limiter 7 outputs a filter difference signal SF3. This filter difference signal SF3 becomes an output signal of the filter unit 7.

The filter difference signal SF3 output from the filter unit 7 is input to the second arithmetic unit 5 and the third arithmetic unit 6. The second arithmetic unit 5 adds the input signal Lin for the left channel and the filter difference signal SF3 and outputs the result as an output signal Lout for the left channel. Further, the third arithmetic unit 6 subtracts the filter difference signal SF3 from the right channel input signal Rin to obtain the right channel output signal Rin.
Output as out.

The output signal Lo output as described above
ut and Rout are output to a speaker (not shown) so that the listener can hear the enlarged sound image.

In the above-described embodiment, the first input signal is the input signal Lin for the left channel and the second input signal is the input signal Rin for the right channel. However, the first input signal is the input signal Rin for the right channel. The input signal Rin may be used, and the second input signal may be used as the left channel input signal Lin. In this case, the first output signal is the right channel output signal Ro.
ut, and the second output signal becomes the left-channel output signal Lout.

[0025]

According to the present invention, according to the present stereo sound image enlarging apparatus, even if the left and right channels are panned with the same phase or with a small phase difference (for example, bass and bass drum sounds), The left and right amplitude ratios do not change and there is no discomfort that is emphasized.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a device using a stereo sound image enlarging device.

FIG. 2 is a schematic diagram of a stereo sound image enlarging device of the present invention.

FIG. 3 is a diagram illustrating frequency characteristics of a low-pass filter.

FIG. 4 is a diagram illustrating frequency characteristics of a high-pass filter.

5A and 5B are diagrams illustrating a combination characteristic obtained by combining a low-pass filter and a high-pass filter, wherein FIG. 5A illustrates a frequency characteristic and FIG. 5B illustrates a phase characteristic.

[Explanation of symbols]

 Reference Signs List 4 first operation unit 5 second operation unit 6 third operation unit 7 filter unit 8 low-pass filter 9 high-pass filter 10 amplitude adjuster

Claims (2)

[Claims] 1. A first operation unit for subtracting a second input signal from a first input signal to generate a difference signal, and filtering the difference signal from the first operation unit to generate a filtered difference signal A filter section for generating, a second operation section for adding the first input signal and a filter difference signal from the filter section to generate a first output signal, and the filter section from a second input signal And a third operation signal for subtracting a filter difference signal from the filter signal, wherein the filter unit has a low-pass filter with a cut-off frequency of 5 kHz and a high-pass filter with a cut-off frequency of 200 Hz. Stereo sound image magnifier. 2. The stereo sound image enlarging device according to claim 1, wherein the filter unit further has a gain adjustment period for adjusting a fluctuation range from 0 to 1.