JPH0634556B2 - Vehicle audio system - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle acoustic device, and more particularly to a vehicle acoustic device that suppresses muffled sound due to standing waves to improve sound quality.

2. Description of the Related Art Conventionally, there is a device called an auto equalizer as a device for improving the sound quality of an audio device provided in a vehicle interior. This device gives a signal whose frequency has been swept to a speaker by a predetermined sweeper, senses the sound pressure of the speaker by a sensor provided on an instrument panel of a vehicle, and based on this, equalizes the frequency characteristic. By making the adjustment, the sound pressure-frequency characteristic is automatically corrected to be flat at the listening position of the occupant.

However, in a space surrounded by wall surfaces composed of a vehicle body member, windshield glass, etc., such as a passenger compartment, a phenomenon in which sound waves of a specific frequency emitted from a speaker are repeatedly attenuated between the opposing wall surfaces and are not easily attenuated, That is, a standing wave is generated, and the reproduced sound reverberates due to the standing wave to generate a so-called muffled sound.

Therefore, in the device that simply corrects the sound pressure-frequency characteristics as described above, the improvement of the overall sound quality can be expected, but the reproduced sound of the specific frequency that causes the standing wave is regulated at all. Therefore, the muffled sound is generated by the standing wave as described above, and the improvement of the sound quality in the specific frequency band cannot be expected at all.

OBJECT OF THE INVENTION The present invention has been made in view of the current state of the device for improving the conventional sound quality, and suppresses the reproduction of the frequency band in which the muffled sound is generated by the standing wave in the vehicle interior, and It is an object of the present invention to provide a vehicle acoustic device capable of improving the sound quality of this specific frequency band by converting the lack of music information caused by the conversion into an acoustic signal that does not affect the source sound and reproducing it. It is a thing.

According to the present invention in order to achieve the above object, in a vehicle acoustic device that amplifies a sound source signal output from an appropriate sound source and reproduces the amplified sound source signal in a vehicle interior. , For an acoustic source that attenuates a frequency signal within a range of a lower limit frequency of a band including one or more standing wave frequencies of interest among the acoustic source signals output from the sound source to an upper limit frequency of the band A filter, and a high-pass filter for a standing wave that filters high-frequency signals having the lower limit frequency or higher among the acoustic source signals,
A low-pass filter for a standing wave that is provided after the high-pass filter for the standing wave and filters a low-frequency signal of the upper limit frequency or lower, and a low-pass filter for the standing wave that is provided after the low-pass filter for the standing wave A harmonic overtone generator that converts the output signal from the low-pass filter into a harmonic overtone signal, an adder that adds the output signal from the harmonic overtone generator and the output signal from the acoustic source filter, and synthesizes them, and from the adder And a speaker that reproduces the output signal of (1) are provided to suppress the generation of standing waves, and at the same time, the loss of music information caused thereby is supplemented by overtones.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention. An acoustic source signal output from a stereo source 1 such as a tuner or a cassette deck is amplified by a preamplifier 2 and then input to a sound quality correction device 4. The output of the sound quality correction device 4 is amplified by the main amplifier 3 and then input to the speakers 5 and 6.

The sound quality correction device 4 includes an upper limit of a band including a predetermined frequency (standing wave frequency) at which a standing wave causing a muffled sound is generated in the amplified acoustic source signal output from the preamplifier 2. A high-pass filter (acoustic source filter) 7 that filters signals in a high frequency band equal to or higher than the upper limit frequency by cutting signals having a frequency equal to or lower than the upper limit frequency, and a band including the standing wave frequency in the same acoustic source signal. There is provided a low pass filter (sound source filter) 8 that cuts a signal having a frequency equal to or higher than the lower limit frequency and filters a signal in a low frequency band equal to or lower than the lower limit frequency. The above frequency band may include one standing wave frequency or may include a plurality of standing wave frequencies.

Further, on the output side of the high-pass filter 7 and the low-pass filter 8, an adder 9 for adding and synthesizing output signals of the both filters 7 and 8 and a harmonic overtone signal described later is provided.

Further, the sound quality correction device 4 includes both filters 7 and 8
Separately, a high-pass filter 10 and a low-pass filter 11 for standing waves are provided. The high-pass filter 10 has a function of passing only a signal in the same high frequency band that is cut by the low-pass filter 8 among the amplified acoustic source signals output from the preamplifier 2, while the low-pass filter 10 is used. Reference numeral 11 has a function of passing only a signal in the same low frequency band that is cut by the high-pass filter 7 among the acoustic source signals.

That is, in the acoustic source signal that has passed through the high-pass filter 7 and the low-pass filter 8, a signal in a band including a predetermined frequency (standing wave frequency) at which a standing wave that causes muffled sound is generated is cut as it is. On the other hand, the acoustic source signal that has passed through the high-pass filter 10 and the low-pass filter 11 is, on the contrary, a signal in a band including a predetermined frequency (standing wave frequency) at which a standing wave that causes muffled sound is generated. Only will be left.

The sound source signal that has passed through the high-pass filter 10 and the low-pass filter 11 is input to a harmonic overtone generator 12 that converts the sound source signal into a harmonic overtone signal, that is, a doubled frequency signal. The signal converted into the overtone by the overtone generator 12 is input to the adder 9 after its output level is adjusted by the level controller 13, and the adder 9 outputs the high pass filter 7 and the high pass filter 7. The harmonic pass signal converted by the harmonic overtone generator 12 is added to the signal that has passed through the low-pass filter 8 to synthesize it, and then the main amplifier 3
It has a function to output to.

In the present embodiment having the above-described configuration, when the acoustic space in which the speakers 5 and 6 are arranged is the vehicle interior R having the width W and the front-rear length L as shown in FIG. Then, among the standing waves, the frequencies (standing wave frequencies) _W and _{L that} are the most problematic for the muffled sound are obtained by the following equations (1) and (2). The width W and the front-rear length L are determined according to the size of the vehicle. _W = V / W (1) _L = V / L (2) And, in general, W <L for passenger cars, so _W >
_L , and the frequency band thereof is usually about 150 Hz < _L < _W <350 Hz.

For the vehicle compartment R, the high pass filter 7
Is set to _W + α, the cutoff frequency of the low pass filter 8 is set to _L −β, and the cutoff frequency of the high pass filter 10 is set to _L −.
β, the cutoff frequency of the low-pass filter 11 is _W +
Set to α (however, both α and β are arbitrary values). The cutoff frequency _W + α is the upper limit frequency of the band including the standing wave frequencies _W and _L , and the cutoff frequency _L −β is the lower limit frequency of the band including the standing wave frequencies _W and _L.

Thus the signal of the generated frequency _W of the standing wave, and at the same time is cut by the high-pass filter 7 is a cut-off frequency _{W +} alpha, passed through the low pass filter 11 is a cut-off frequency _{W +} alpha. On the other hand, the signal of the standing wave frequency _L is cut by the low-pass filter 8 having the cutoff frequency _L + β and, at the same time, passes through the highpass filter 10 having the cutoff frequency _L −β.

Therefore, the signal in the band including the standing wave frequencies _{W 1} and _{L 2} is cut by the filters 7 and 8 on the one hand and is band-passed by the filters 10 and 11 on the other hand at the same time. The signals in the band including the standing wave frequencies _{W 1} and _{L 2} that have passed through both filters 10 and 11 are converted into overtone signals by the overtone generator 12, adjusted to an appropriate level by the level controller 13, and then added. 9
Entered in. Therefore, in the adder 9, the source sound signal in which the signals in the band including the standing wave frequencies _{W 1} and _L are blocked by the filters 7 and 8 and the overtone signal in only the band including the standing wave frequencies _{W 1} and _{L 2} are included. Is input, and the adder 9 adds the source sound signal and the overtone signal and synthesizes them, and then outputs them to the speakers 5 and 6 through the main amplifier 3.

Therefore, the speakers 5 and 6 do not reproduce the signals of the specific standing wave frequencies _{W 1} and _{L that} cause the muffled sound, and the muffled feeling of the reproduced sound due to the standing waves can be eliminated. Further, the signal in the band including the standing wave frequencies _{W 1} and _{L 2} which are to be omitted due to the filtering action of the high pass filter 7 and the low pass filter 8 is reproduced as an overtone, that is, one octave treble. Therefore, the music information that is missing due to the non-reproduction of the signal in the band including the standing wave frequencies _{W 1} and _{L 2} is compensated by the overtones, so that no discomfort is caused and the muffled sound can be eliminated as described above. You can do it.

Strictly speaking, the standing wave frequency also changes depending on the vehicle interior conditions such as temperature and the number of passengers, but as described above, the standing wave frequency is basically determined by the speed of sound and the vehicle interior size. The influence of temperature and occupant volume on the standing wave frequency is not a problem.

FIG. 3 shows a second embodiment of the present invention, in which the high pass filters 7a and 7b, the low pass filters 8a and 8b, the adders 9a and 9b, the high pass filters 10a and 10b and the low pass filters 11a and 11b, and the overtone generator. 12
a, 12b and level controllers 13a, 13b are respectively provided in the first sound quality correction device 4a and the second sound quality correction device 4b, and the first sound quality correction device 4a is arranged in series.
This suppresses the standing wave of the frequency _W that occurs in the width direction of the vehicle compartment R, and the vehicle interior R is corrected by the second sound quality correction device 4b.
The standing wave of the frequency _L generated in the front-back direction is suppressed.

The cutoff frequency of each filter in the second embodiment is as shown in Table-1.

According to the second embodiment having the above configuration, the first sound quality correction device 4a cuts off the signal in the band including the standing wave frequency _W and at the same time converts it into the overtone, and the second sound quality correction is performed. The signal in the band including the standing wave frequency _L is cut off by the device 4b, and at the same time converted into an overtone. Therefore, the passenger compartment R
The sound quality correction in the width direction and the sound quality correction in the front-back direction are performed independently by the dedicated sound quality correction devices 4a and 4b, and only the signals closest to the standing wave frequencies _{W 1} and _{L 2} are cut, and the extra frequencies are removed. The signal of is not cut, the muffled sound can be reliably eliminated, and a clear reproduced sound can be obtained.

FIG. 4 shows a third embodiment of the present invention, in which a plurality of overtone generators 12, 12, ... Are arranged in series, and the output level of each overtone generator 12, 12 ,. Controllers 13, 13 ... Are provided and each overtone generator 12, 1
Each level controller 1 converts the overtone converted signal in 2 ...
The level is adjusted at 3, 13, ... And then input to the adder 9.

According to the third embodiment, there is an advantage that a more natural reproduced sound can be obtained by superimposing the reproduced sound of 2 times, 4 times, 6 times ...

FIG. 5 shows a fourth embodiment of the present invention, which is an application of the fact that the muffled sound due to a standing wave can be eliminated by reducing the sound pressure level of the specific standing wave frequency to some extent. is there.

That is, in the fourth embodiment, the filter 14 is used as the acoustic source filter without using the high-pass filter 7 and the low-pass filter 8 that cut the signal of the specific standing wave frequency as in the first embodiment. I am using. In the passenger compartment R, the filter 14 is a signal in a band including the standing wave frequencies _{W 1} and _{L 2,} that is, a frequency.
_It has a function of reducing the sound pressure level of the signal in the band from _L −β (lower limit frequency) to _W + α (upper limit frequency) to a predetermined sound pressure level at which muffled noise does not occur.

In the fourth embodiment having the above configuration, the sound pressure level of the signal in the frequency band from _L −β to _W + α is reduced by the filter 14 as described above, so that the speakers 5, 6 Even if it is reproduced as it is, the muffled sound due to the standing wave is not generated, and the fundamental tone is also radiated within the range where the muffled sound is not generated.

At the same time, the signals in the frequency band from _L −β to _W + α that have passed through the high-pass filter 10 and the low-pass filter 11 are converted into overtones by the overtone generator 12, and then added and synthesized by the adder 9. Since the sound is radiated from the speakers 5 and 6 via the main amplifier 3, the insufficient sound pressure of the sound source signal due to the sound pressure level reducing function of the filter 14 is compensated by overtones.

Therefore, in this fourth embodiment, from _L- β
_In addition to the overtone signal of the signal in the frequency band up to _W + α (the band including the standing wave frequencies _{W 1} and _{L 2} ), the fundamental tone in that band can remain in the reproduced sound even though the sound pressure level is low. It is possible to obtain a natural reproduced sound that is closer to the source sound.

In the first, second and fourth embodiments, the output signal of the low-pass filter 11 (11a, 11b) is subjected to harmonic overtone conversion by the harmonic overtone generator 12, that is, it is converted to a signal of double frequency. However, the present invention is not limited to this, and if the sound is an even-numbered overtone, a reproduced sound that does not cause a feeling of strangeness can be obtained.

EFFECTS OF THE INVENTION As described above, the present invention attenuates a frequency signal in a band including a specific standing wave frequency among acoustic source signals output from an appropriate acoustic source with an acoustic source filter, while Among the signals, only the signal in the band including the specific standing wave frequency is taken out by the standing wave high-pass filter and the standing wave low-pass filter, and then converted into the overtone signal by the overtone generator, and this overtone signal is generated. Since the sound source signal attenuated by the sound source filter and the sound source signal are added and synthesized before being reproduced, a muffled sound is generated in a vehicle interior where a standing wave is easily generated and muffled sound is generated. The signal in the frequency band that causes the noise is cut off, and a clear reproduced sound can be obtained.

Moreover, since the signal in the frequency band to be attenuated as described above is converted into the overtone which does not have a musical influence, and is reproduced separately, a feeling of strangeness may occur due to the partial loss of the music information. Without, you can get a natural reproduced sound.

In addition, in the second embodiment, since the standing wave suppression and the harmonic conversion are individually performed for each different standing wave frequency, only the signal closest to the standing wave frequency is cut. As a result, even a signal with an extra frequency is not cut, and clear muffled sound can be obtained along with elimination of muffled sound.

In addition, in the third embodiment, since a plurality of overtone generators are used, it is possible to reproduce sounds of 2 times, 4 times, 6 times, ... There is an advantage that sound can be obtained.

Further, in the fourth embodiment, in addition to the overtone signal of the signal of the band including the specific standing wave frequency, the fundamental tone of the band can be left in the reproduced sound although the sound pressure level is low. Therefore, a natural reproduced sound closer to the source sound can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of the present invention, FIG. 2 is a plan view of a passenger compartment, FIG. 3 is a block diagram showing a second embodiment of the present invention, and FIG. Is a block diagram showing a third embodiment of the present invention, and FIG. 5 is a block diagram showing a fourth embodiment of the present invention. 1 ... stereo source (sound source), 2 ... briamp,
3 ... Main amplifier, 4, 4a, 4b ... Sound quality correction device,
5, 6 ... Speaker, 7, 7a, 7b ... High pass filter (sound source filter), 8, 8a, 8b ... Low pass filter (sound source filter), 9 ... Adder, 1
0, 10a, 10b ... High-pass filter (standing wave high-pass filter), 11, 11a, 11b ... Low-pass filter (standing wave low-pass filter), 12, 12a, 1
2b ... Overtone generator, 13, 13a, 13b ... Level controller, 14 ... Filter (sound source filter).

Claims (1)

[Claims] 1. A vehicle acoustic device for amplifying a sound source signal output from an appropriate sound source and reproducing the amplified sound source signal in a vehicle compartment, wherein the sound output from the sound source (1). Of the source signals, an acoustic source filter (7, 7) for attenuating a frequency signal within a range from a lower limit frequency of a band including one or a plurality of target standing wave frequencies to an upper limit frequency of the band.
8), a high-pass filter for a standing wave (10) for filtering a high-frequency signal having a frequency equal to or higher than the lower limit frequency of the acoustic source signal, and the upper limit frequency provided in a stage subsequent to the high-pass filter for the standing wave (10). A standing wave low-pass filter (11) for filtering the following low-frequency signals, and an output signal from the standing wave low-pass filter (11), which is provided at a stage subsequent to the standing wave low-pass filter (11), An overtone generator (12) for converting into an overtone signal, and an adder (9) for adding and synthesizing an output signal from the overtone generator (12) and an output signal from the acoustic source filter (7, 8). ) And a speaker (5, 6) for reproducing the output signal from the adder (9), and a vehicle acoustic device.