JP3386618B2 - Sound reproduction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound reproducing apparatus which emits a sound corresponding to an audio signal input from a speaker to an acoustic space, and particularly to reproduction of a low-frequency component, for example, a low-frequency component lower than a resonance frequency of the speaker. The present invention relates to a sound reproducing device capable of improving quality.

[0002]

2. Description of the Related Art In a conventional sound reproducing apparatus, a loudness compensating circuit, a bass increasing circuit (graphic equalizer), and the like are used as means for improving reproduction quality in a low frequency range. In other words, a reproduction signal in a desired frequency band (low sound range) is reproduced by making these circuits electrically larger than other frequency bands, thereby improving the reproduction quality in the low sound range.

[0003]

With respect to an electric circuit, it is possible to arbitrarily manipulate the characteristics of a desired frequency band by taking the above method. However, in the sound reproducing device, the signal processed in this way is finally supplied to a speaker and reproduced as sound. Therefore, even if the signal is processed without considering the electro-acoustic conversion characteristics of the speaker, the quality of the sound finally reproduced is rarely improved as expected. This cause is governed by the resonance frequency f ₀ of the speaker. The reproduction frequency characteristic of the speaker greatly changes around the resonance frequency f ₀ (about 100 Hz). That is, in the frequency band equal to or lower than the resonance frequency f ₀ , the sound pressure of the reproduced sound is significantly reduced (see FIG. 4A), and the reproduction distortion is greatly increased (FIG. 4A).
(See (b)). FIG. 5 shows detailed f characteristics of the speaker.

For this reason, when the bass range is enhanced by an equalizer due to lack of bass below the resonance frequency f ₀ (FIG. 4 (c)
), The sound is slightly enhanced, but the distortion is further increased and the quality of the reproduced sound is degraded. That is, the graphic equalizer and loudness compensation circuit and the like, effective sound pressure be supplied enhanced how the resonance frequency f ₀ following the signal component of the speaker can not be expected, on the contrary, the reproduction distortion increases And the quality of the reproduced sound is greatly impaired. Such a phenomenon is particularly caused by a sound reproducing apparatus (for example, a radio-cassette or a television) using a small-diameter speaker having a relatively high resonance frequency or a vehicle-mounted vehicle in which it is difficult to secure a sufficient volume of a so-called enclosure for mounting the speaker. Remarkably appear in such reproduction devices.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a sound reproducing apparatus capable of improving the reproduction quality of low-frequency components, especially low-frequency components below the resonance frequency of a speaker. Another object of the present invention is to provide a sound reproducing apparatus that can improve the reproduction quality of low frequency components with a simple configuration.

[0006]

SUMMARY OF THE INVENTION According to the present invention, an audio signal is reduced to a low frequency below a resonance frequency of a speaker.
A separation circuit that separates the high-frequency component and the high-frequency component above the resonance frequency of the speaker, a frequency multiplication circuit that multiplies the audio signal frequency of the low-frequency component, and a high-frequency component and the output of the frequency multiplication circuit are combined and output to the speaker side. This is achieved by a sound reproducing device having a synthesizing unit for outputting.

[0007]

The audio signal is separated into a low-frequency component and a high-frequency component by a separation circuit (a band-pass filter and a high-pass filter), and the audio signal frequency of the low-frequency component is multiplied (for example, doubled) by a frequency multiplication circuit. Synthesizes the high frequency component and the output of the frequency multiplier circuit and outputs the result to the speaker side.
If the frequency of the low-frequency audio signal below the resonance frequency f _{0 of the} speaker is multiplied (for example, doubled) and the frequency-multiplied audio signal is input to the speaker, the speaker generates a sound corresponding to the frequency-multiplied audio signal. Emit correctly into the acoustic space. By the way, it has been proven that if only harmonics of the fundamental tone are output psychoacoustically, humans can perceive the sound as if there is a fundamental tone without the fundamental tone. For this reason, the listener recognizes a fundamental sound, that is, a low-frequency sound having a resonance frequency f ₀ or lower than a sound corresponding to the frequency-multiplied signal. In this way, no low-frequency audio signal having a resonance frequency f ₀ or less is input to the speaker, so that there is no distortion, and low-frequency audio having a resonance frequency f ₀ or less can be recognized by a psychoacoustic effect.
The bass reproduction quality can be improved.

[0008] In addition, by synthesizing the delayed high-frequency component with the frequency-multiplied audio signal for the time required for the frequency multiplication and outputting the resultant signal, it is possible to hear a sound without a time lag. Furthermore, if the gain of the audio signal frequency-multiplied by the variable gain amplifier can be adjusted, the bass can be increased or decreased according to the listener's preference.

[0009]

【Example】

(a) Principle of the present invention It is better not to force an audio signal component that cannot be output from a speaker into the speaker. However, this would be cut the resonance frequency f ₀ following the low-frequency signal component of the speaker included in the actual audio signal is unable to hear the bass. Therefore, it is best if the listener can hear the low-frequency signal component below the resonance frequency without inputting the low-frequency signal component to the speaker by any method.
By the way, it has been proven that if only harmonics of the fundamental tone are output psychoacoustically, humans can perceive the sound as if there is a fundamental tone without the fundamental tone. For example, the timbre is determined by the fundamental tone and its harmonics, but if the harmonics can be accurately reproduced without the fundamental tone, a human can correctly recognize the sound of the instrument.

According to the psychoacoustic theory, the frequency of a low-frequency audio signal having a resonance frequency f ₀ or less of the speaker is multiplied (for example, doubled), and the multiplied signal is input to the speaker, so that the speaker can accurately output the signal. the sound corresponding to the emitted acoustic space, the listener recognizes the fundamental i.e. resonant frequency f ₀ following low-band speech from sound according to該逓doubled signal. As a result, the listener can recognize the bass without distortion, and can improve the reproduction quality of the bass.

(B) Overall configuration FIG. 1 is a block diagram of the sound reproducing apparatus of the present invention, and FIG.
FIG. In FIG. 1, reference numeral 11 denotes a passage above the frequency fc.
It is a high-pass filter (H.P.F)
fc is the resonance frequency f of the speaker, for example.₀(Approx. 100Hz)
(See FIG. 2 (b)). 12 is a pass band fc₁~ Fc_TwoNo ba
Frequency fc on the high frequency side with a low-pass filter (B.P.F)._TwoIs
Speaker resonance frequency f₀(About 100Hz)
Wave side frequency fc₁Is the frequency multiplication rate to be described later.
If fc₁= F₀/ A (see FIG. 2B). That is, fc = f₀ fc₁= F₀/ A fc_Two= F₀ And

Reference numeral 13 denotes a frequency multiplying circuit for multiplying the frequency of the low-frequency audio signal passed through the band-pass filter 12 by a. Preferably, a is an integer, for example, a = 2. The multiplication factor a = 2 and the resonance frequency f _{0 of the} speaker
Is 100 Hz, fc = 100 Hz, fc ₁ = 50 Hz, fc ₂ = 100
Hz. Reference numeral 14 denotes a delay circuit (DELAY) that delays the middle and high frequency components output from the high-pass filter 11 by the time required for the frequency multiplication, and 15 denotes a gain that controls the amplitude of the frequency-multiplied audio signal output from the frequency multiplication circuit 13. A variable amplifier 16 is an amplifier (gain may be variable), and 17 is a synthesizing unit, which synthesizes a signal input via the amplifiers 15 and 16 and outputs the synthesized signal to the speaker.

(C) Operation of the Sound Reproducing Apparatus The audio signal Sin having a flat frequency characteristic (FIG. 2A) output from an audio source such as a tape player, a CD player, and an FM tuner is converted into a high-pass filter 11 and a band-pass signal. Input to the filter 12. The high-pass filter 11 removes low frequency components below fc (= 100 Hz) and passes audio signal components higher than 100 Hz, that is, higher than the middle low frequency range. On the other hand, the band-pass filter 12 extracts and outputs low-frequency components at frequencies fc _{1 to} fc ₂ (= 50 Hz to 100 Hz) (see FIG. 2C). The frequency multiplying circuit 13 multiplies the frequency of the low frequency range component passed through the band-pass filter 12 by a, for example, twice. Thus, the original fc ₁ to fc ₂
(= 50Hz~100Hz) bass signal is, 2fc ₁ ~2fc ₂ (=
(100Hz ~ 200Hz)
(See FIG. 2 (d)). Thereafter, the frequency-multiplied signal is input to the synthesizing unit 17 via the variable gain amplifier 15.

On the other hand, the delay circuit 14 is a high-pass filter 1
The mid-high range component that has passed through 1 is delayed by the time required for frequency multiplication, and input to the synthesis unit 17 via the amplifier 16. The combining unit 17 combines the outputs of the frequency multiplier 13 and the delay circuit 14 input via the amplifiers 15 and 16 (FIG. 2 (e)).
), And inputs the synthesized signal Sout to an audio circuit (equalizer, electronic volume circuit, etc.) on the speaker side (not shown), and finally to the speaker.

If only harmonics of the fundamental tone are output psychoacoustically, a human can feel the sound as if there is a fundamental tone without the fundamental tone. For this reason, the listener recognizes a fundamental sound, that is, a low-frequency sound having a resonance frequency f ₀ or less of the speaker, from a sound corresponding to the frequency-multiplied signal. As a result, even if the resonance frequency f ₀ following low-band speech signal without input to the speaker, can recognize the low-band speech follows the resonance frequency f ₀ by psychoacoustic effects, moreover, the input low frequency audio signal to the speaker As a result, there is no distortion and excellent bass reproduction is possible.
Also, by delaying the high frequency component by the time required for the frequency multiplication and synthesizing it with the frequency-multiplied audio signal and outputting the resultant signal, it is possible to hear a sound without a time lag.
If it is desired to increase or decrease the bass according to the listener's preference, a knob for varying the gain is provided on the operation unit, and the knob is operated to adjust the gain of the variable gain amplifier 15 to increase or decrease the bass.

(D) Frequency Multiplying Circuit FIG. 3 is a block diagram of the frequency multiplying circuit 13. Reference numeral 13a denotes an AD converter (AD) that samples a low-frequency audio signal component output from the band-pass filter 12 at a predetermined sampling rate Sp and converts it into digital data.
C), 13b and 13c are first and second memories which store digital audio data alternately in a time series at predetermined time intervals T, and 13d alternately store digital data output from the AD converter 13a at every cycle T. First and second memories 13
a data allocating unit 13b for allocating the digital data to each of the first and second memories 13b and 13c at a speed Sp for each cycle T; This is a DA converter (DAC) that converts digital data output from the unit into analog data.

The A / D converter 13a continuously converts low-frequency audio signal components into digital data at a sampling rate Sp, and the data distribution unit 13d first inputs and stores the A / D-converted audio data in the first memory 13b. Let it. When audio data for one cycle T is stored in the first memory 13b, the thinning-out reading unit 13e
, The audio data is repeatedly read out from the first memory 13b every other data at the read speed Sp, and at the same time, the data distribution unit 13d stores the audio data from the AD converter 13a in the second memory 13c. The thinning-out reading unit 13e reads out the same data twice during one cycle T to repeatedly read out the data every other unit, and the frequency of the audio data is doubled and input to the DA converter 13f.

When one cycle is completed, a switching signal CHG is generated, and the data distribution unit 13d stores the audio data in the first memory 13b.
"e" repeatedly reads audio data from the second memory 13c every other data at the read speed Sp. Thereafter, the storage and the thinning-out reading of the audio data are repeated. The DA converter 13f includes a thinning-out reading unit 13e.
Is converted into an analog audio signal at a speed Sp and output. As a result, the low-frequency audio signal of 50 to 100 Hz input from the band-pass filter 12 is converted into a signal having a frequency component of 100 to 200 Hz. In addition, the speed 2 ·
It is also possible to adopt a configuration in which audio data is continuously read at Sp, DA converted, and output.

(E) Modified Example In the above description, the case where the frequency multiplication ratio a = 2 has been described. However, the frequency is not limited to 2, and the frequency can be converted to a signal of an integer multiple or another multiple. Further, in the above, the low-frequency component of the audio signal to the boundary of the resonance frequency f ₀ of the speaker, there is no need has been separated in the high-frequency component separating necessarily boundary f _0, more, or separated by less frequency Alternatively, a part of the low band and a part of the high band may be overlapped. As described above, the present invention has been described with reference to the embodiments. However, the present invention can be variously modified in accordance with the gist of the present invention described in the claims, and the present invention does not exclude these.

[0020]

As described above, according to the present invention, an audio signal is separated into a low-frequency component and a high-frequency component, the audio signal frequency of the low-frequency component is doubled (for example, doubled), and the high-frequency component and the output of the frequency multiplying circuit are output. Is synthesized and output to the speaker side, so that the low-frequency voice can be recognized psychoacoustically from the sound corresponding to the frequency-multiplied signal, and the low-frequency voice signal having the resonance frequency f0 or less is not input to the speaker. Therefore, it is possible to listen to an excellent bass without distortion, and to improve bass reproduction quality. In particular, even a speaker having a relatively low bass reproduction capability can provide good bass reproduction quality with a simple configuration. In other words, only general home sound reproducers
Instead , use a small-diameter speaker with a relatively high resonance frequency.
Have sound reproducing apparatus (for example, radio cassette player and television) and, spin
The capacity of the enclosure for mounting the
Various sounds such as in-vehicle playback devices that are difficult to secure
To the reproducing apparatus, and supplies an accurate, high-quality low-frequency sound reproduction quality
be able to. Also, according to the present invention, since high-frequency components are delayed by the time required for frequency multiplication and synthesized with the frequency-multiplied audio signal to be output, it is possible to listen to sound without time lag. Can be. Further, since the gain of the frequency-multiplied audio signal is configured to be adjustable, the bass can be increased or decreased according to the listener's preference.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a sound reproduction device of the present invention.

FIG. 2 is a diagram illustrating the operation of the present invention.

FIG. 3 is a configuration diagram of a frequency multiplier.

FIG. 4 is an explanatory diagram of a conventional problem.

FIG. 5 is a detailed diagram of a frequency characteristic of a speaker.

[Explanation of symbols]

11. High-pass filter 12. Bandpass filter 13. Frequency multiplying circuit 14..Delay circuit 15 ・ ・ Gain variable amplifier 16 ・ ・ Synthesis unit

Continuation of the front page (56) References JP-A-63-314099 (JP, A) JP-A-5-328481 (JP, A) JP-A-50-130402 (JP, A) JP-A-5-266582 (JP JP-A-1-186008 (JP, A) JP-A-5-199576 (JP, A) JP-A-5-122782 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) H03G 5/02 H04R 3/00 310 H04R 3/04

Claims (4)

(57) [Claims] A sound reproducing apparatus that emits a sound corresponding to an audio signal input from a speaker to an acoustic space, wherein the audio signal is converted to a low-frequency component equal to or lower than a resonance frequency of the speaker.
A separation circuit that separates the high frequency component above the resonance frequency of the speaker and the speaker, a frequency multiplier that multiplies the audio signal frequency of the low frequency component, and a high frequency component and the output of the frequency multiplier are combined and output to the speaker side A sound reproducing device comprising a synthesizing unit. 2. The sound reproducing apparatus according to claim 1, wherein said frequency multiplying circuit multiplies an audio signal frequency by an integer. 3. A time period required for the frequency multiplication, a delay unit for delaying the high frequency components, the combining unit sound reproducing apparatus according to claim 1, wherein the outputting by synthesizing the frequency multiplier output the delay unit . 4. The sound reproducing apparatus according to claim 3, further comprising a gain control circuit for adjusting a gain of the frequency-multiplied audio signal.