JP2006270698A - Low frequency sound emphasizing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low frequency sound emphasizing device for emphasizing a sense of low sound frequencies by compensating the reduction of a low frequency characteristic of a speaker without upsizing the speaker and a power amplifier for driving the speaker. <P>SOLUTION: A phase inversion means 3 and a first low pas filter 4 extract a low frequency signal at the outside of a reproduction frequency band of the speaker, a harmonic generating means 5 applies nonlinear arithmetic operations to the extracted signal in a way of asymmetry with respect to the origin wherein the input and output characteristic of the means 5 passes through the origin and has a break point at least at one point or over other than the origin, and the harmonic generating means 5 applies subtraction processing to the signal subjected to the nonlinear arithmetic operation and the extracted signal respectively at a proper multiple to attenuate the fundamental wave and produce second and third harmonics, and summates the produced harmonics to the original signal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a bass enhancement device that aurally compensates for a decrease in low-frequency characteristics of a speaker and enhances the bass feeling without increasing the size of a speaker or a power amplifier that drives the speaker.

  In recent years, audio devices have been miniaturized, and in particular, there has been a problem that sufficient low-frequency reproduction cannot be performed due to restrictions on the size of speakers. In order to solve this problem, a system with a low-frequency reproduction dedicated speaker that can be installed at a position other than the front and a power amplifier that drives the low-frequency reproduction using the fact that the directivity of the low frequency is ambiguous. Although it is sold, it has problems such as requiring an installation place and being expensive, and there is an increasing demand for downsizing in such a system.

  As a method for compensating for a decrease in the low frequency characteristic of the speaker and enhancing the low tone, there is a simplest method of increasing the low frequency gain using an equalizer. However, in order to enhance the low-frequency sound outside the reproduction frequency band of the speaker, it is necessary to significantly increase the low-frequency gain, which requires a large power output, and there is a problem that the power amplifier that drives the speaker increases in size. is doing. Along with this, it is necessary to increase the allowable input of the speaker, and there is a problem that the speaker is also increased in size.

  In response to these problems, low-frequency signals outside the reproduction frequency band of the speaker are extracted as a method of enhancing the low-frequency sound outside the reproduction frequency band of the speaker without increasing the size of the speaker and the power amplifier that drives the speaker. A method for adding the harmonics is disclosed in Patent Document 1. FIG. 15 is a block diagram of a bass enhancement device disclosed in Patent Document 1. Hereinafter, a conventional bass enhancement device will be described with reference to FIG.

  First, the left and right audio signals input to the apparatus are input to the second adding means 32, and the left and right signals are added. The signal output from the second adding means 32 is input to the first low-pass filter 33, and a low-frequency signal outside the reproduction frequency band of the speaker is extracted. The signal output from the first low-pass filter 33 is input to the full-wave rectifier 35 that is the harmonic generation means 34, and the input / output characteristics are an even function that is symmetric with respect to the output axis. Converted to second harmonic. The signal output from the full-wave rectifier 35 is input to the second low-pass filter 36, and harmonics other than the second harmonic are cut, and only the second harmonic is extracted. The signal output from the second low-pass filter 36 is input to the first adding means 37 and 38 and added to the left and right signals input to the apparatus. In this way, the second harmonic of the low frequency signal outside the reproduction frequency band of the speaker can be added to the input audio signal.

Further, as a method of controlling the harmonic level to be generated, after adding an offset to the extracted signal, a signal obtained by multiplying each positive and negative half-wave component by an appropriate value is added to the extracted signal to generate a harmonic. A method is shown in US Pat.
JP-A-8-237800 Japanese Patent No. 3462590

  However, the method described in Patent Document 1 adds only the second harmonic. In psychoacoustics, it is known that humans can feel the fundamental tone even when the fundamental tone (fundamental wave) is not emitted and only its harmonics are emitted. For example, when a speaker that cannot reproduce 70 Hz or less is reproduced by adding 50 Hz second harmonic and third harmonics 100 Hz and 150 Hz, a human can feel a fundamental frequency of 50 Hz. However, when reproduction is performed by adding the second and fourth harmonics 100 Hz and 200 Hz, 100 Hz is fundamentally recognized and 200 Hz is the second harmonic, and the fundamental is 50 Hz. I can't feel it. Further, when only the second harmonic, 100 Hz, is reproduced, 100 Hz is mistakenly recognized as a fundamental tone, and the fundamental tone, 50 Hz, cannot be felt. Thus, in order to apply the psychoacoustics to compensate for the lowering of the low frequency characteristics of the loudspeaker and to enhance the bass feeling, it is necessary to add the second harmonic and the third harmonic.

  As described above, the method of Patent Document 1 in which only the even-order harmonics mainly including the second-order harmonics are added has a problem that the effect of enhancing the bass tone of the fundamental tone outside the reproduction frequency band of the speaker is weak.

  In addition, in order to realize the method described in Patent Document 2, there is a problem that the circuit scale becomes large, and not only harmonics but also fundamental waves are generated from the extracted signal.

  The basic concept of the present invention is that when the low frequency range of the reproduction frequency characteristic of the speaker does not extend to the range of the fundamental wave as shown in FIG. 14, the second harmonic and the third harmonic of the fundamental wave of the original signal. By generating harmonics, it is recognized as if the fundamental wave is present, and the low frequency characteristics of the speaker are compensated for and the bass tone is enhanced without increasing the size of the speaker and the power amplifier that drives it. An object is to provide a bass enhancement device.

In order to respond to the above object, the bass enhancement device of the present invention compensates for the lowering of the low frequency characteristics of the speaker and enhances the bass feeling without increasing the size of the speaker and the power amplifier that drives the speaker. A low-frequency signal outside the reproduction frequency band is extracted, and the extracted signal passes through the origin on the input and output, and the origin is asymmetrically nonlinear with at least one break point other than the origin. By subtracting the extracted signal and the extracted signal at an appropriate magnification, the fundamental wave is attenuated to generate harmonics including the second and third harmonics. Then, by adding the generated harmonics to the original signal,
When the input signal level is high, harmonics including the second and third harmonics of the low frequency signal outside the reproduction frequency band of the speaker are added, and when the input signal level is low, the low frequency gain Is the main feature.

The bass enhancement device of the present invention attenuates the fundamental wave by performing the above-described processing on the low-frequency signal included in the band where the low-frequency characteristics of the speaker are reduced, and thereby the second harmonic and the third harmonic. By generating harmonics including harmonics and adding the generated harmonics to the original signal,
When the input signal level is large in a small-scale calculation, the harmonics including the second and third harmonics of the low frequency signal outside the reproduction frequency band of the speaker are added, and the input signal level is small. In this case, there is an advantage that the low-frequency gain is increased, and the low-frequency feeling can be enhanced by compensating for a decrease in the low-frequency characteristics of the speaker without increasing the size of the speaker and the power amplifier for driving the speaker at low cost.

(Embodiment 1)
1 is a block diagram of a bass enhancement device according to Embodiment 1 of the present invention, FIG. 2 is a circuit diagram of its inverting addition amplifier, FIG. 3 is a circuit diagram of its nonlinear arithmetic means, and FIG. 4 is a nonlinear diagram of FIG. FIG. 5 is a spectrum diagram when a single sine wave is input to the nonlinear arithmetic means of FIG. 3, FIG. 6 is a circuit diagram of the harmonic generation means, and FIG. FIG. 8 is a spectrum diagram when a single sine wave is input to the harmonic generation means of FIG.

  Hereinafter, the bass enhancement device of the present invention will be described with reference to FIGS. 1 and 2 to 8. First, the left and right audio signals input to the bass enhancement device are two signals: a signal input from the input terminals T1 and T2 to the first adding means 11 and 12, respectively, and a signal input to the harmonic adding unit 1. Fork.

  The harmonic addition unit 1 includes a second addition unit 2, a phase inversion unit 3, a first low pass filter 4, a harmonic generation unit 5, and a second low pass filter 10. The left and right audio signals input to the adding unit 1 are input to the second adding unit 2 and added. The signal output from the second adding means 2 is input to the phase inverting means 3 and the phase is inverted.

  FIG. 2 is a circuit diagram of the inverting and adding amplifier, in which the functions of the second adding means 2 and the phase inverting means 3 are combined. Audio signals are added and added to one end of each of the resistors R11 and R12 and input to the inverting input terminal of the IC 11, and the non-inverting input of the IC 11 is grounded. A resistor R13 is connected from the output terminal to the inverting input terminal.

  The signal output from the phase inverting means 3 is input to the first low-pass filter 4, and the cutoff frequency is set so as to extract a low-frequency signal outside the reproduction frequency band of the speaker. In order not to increase the circuit scale, the first low-pass filter 4 uses a second order filter. Here, the first low-pass filter 4 causes no phase delay in the pass band, and the phase is delayed by 180 ° in the cutoff band. Including the phase inversion action by the phase inversion means 3, the phase advances by 180 ° in the low frequency range outside the reproduction frequency band of the speaker, which is a band below the cutoff frequency of the first low pass filter 4, and the first low frequency pass There is no phase delay in the band within the reproduction frequency band of the speaker, which is a band higher than the cutoff frequency of the filter 4.

  The signal output from the first low-pass filter 4 is input to the harmonic generation means 5. The harmonic generation unit 5 includes a non-linear calculation unit 6, a first coefficient unit 7, a second coefficient unit 8, and a linear calculation unit 9.

  The nonlinear arithmetic means 6 is constituted by a positive / negative asymmetric limiter circuit so that its input / output characteristics pass over the origin, has break points at least one place other than the origin, and is asymmetric with the origin. In the circuit diagram of the non-linear operation means 6 of FIG. 3 showing one example, the configuration is a diode limiter circuit using a parallel circuit of a resistor R20 and a diode D21 connected in series with the resistor R21. Here, when the input voltage is equal to or less than a negative constant voltage, the diode D21 becomes conductive as shown in FIG. 4, and the output amplitude is limited. As a result, the input / output characteristic passes over the origin, becomes asymmetrical with respect to the origin and asymmetric with respect to the output shaft, and can generate odd-order harmonics and even-order harmonics.

  As shown in FIG. 5, the spectrum when a single sine wave is input to the nonlinear arithmetic means 6 is the same frequency signal as the signal input to the nonlinear arithmetic means 6 in the signal output from the nonlinear arithmetic means 6. Some fundamental waves are also included. Here, if a lot of fundamental waves are included, when the signal is output from the high-frequency adding unit 1, an audio signal input from the input terminals T 1 and T 2 to the first addition means 11 and 12 described later and In spite of being a low-frequency signal outside the reproduction frequency band of the speaker, the gain is increased and output from the apparatus, and becomes a burden on the speaker and the amplifier that drives it at the time of large output.

  Therefore, the signal inputted to the nonlinear arithmetic means 6 by the first coefficient unit 7 is multiplied by a predetermined magnification, the signal outputted from the nonlinear arithmetic means 6 by the second coefficient unit 8 is multiplied by a predetermined magnification, By subtracting the signal output from the first coefficient unit 7 from the signal output from the second coefficient unit 8 by the linear calculation unit 9, the fundamental wave included in the signal output from the nonlinear calculation unit 6 is obtained. Attenuate. Thereby, the harmonic generation means 5 has a low fundamental wave signal level, and can generate harmonics including the second harmonic and the third harmonic.

  The circuit diagram of the harmonic generation means 5 shown in FIG. 6 shows an example in which a differential amplifier is used for the linear calculation means 9. The first coefficient unit 7 sets the coefficients by resistors R24 and R25, and the second coefficient unit 8 sets the coefficients by resistors R22 and R23. The linear operation means 9 includes an IC 21 and resistors R26 and R27 as differential amplifiers. The output of the first coefficient unit 7 is on the inverting input side of the IC 21 and the output of the second coefficient unit 8 is on the non-inverting input side. And the former is subtracted from the latter. The input / output characteristics of the harmonic generation means 5 are shown in FIG. 7, and the spectrum when a single sine wave is input to the harmonic generation means 5 is shown in FIG. It can be seen from FIG. 8 that the signal level of the fundamental wave is reduced and output from the harmonic generation means 5.

  As can be seen from FIG. 7, the harmonic generation means 5 has an input / output characteristic that passes over the origin, has break points at least at one place other than the origin, is asymmetric at the origin, and has an absolute value of the input signal level constant. When the input signal level is below the value, it has a linear characteristic. When the absolute value of the input signal level is above a certain value, it has a characteristic that the input / output characteristic turns back in the direction intersecting the input axis at the time of negative input. For this reason, when the input signal level is small, the linearity is maintained, the amplitude is not suppressed, and no harmonics are generated. On the other hand, when the input signal level is high, the negative input voltage signal is output as a positive output voltage, the peak-to-peak amplitude is suppressed, and harmonics are generated.

  That is, when the signal level input to the harmonic generation means 5 is large, the fundamental wave level with respect to the input signal level is small and the harmonic level is large. On the other hand, when the signal level input to the harmonic generation means 5 is small, the fundamental wave level relative to the input signal level is large and the harmonic level is small.

  The coefficients of the first coefficient unit 7 and the second coefficient unit 8 are set so that the fundamental wave is most attenuated by the linear calculation unit 9 when the signal level input to the harmonic generation unit 5 becomes maximum. As a result, when the signal level input to the harmonic generation means 5 is the maximum, the fundamental wave level is reduced and a harmonic is generated. As the signal level input to the harmonic generation means 5 decreases, the fundamental wave level with respect to the input signal level increases and the harmonic level decreases.

Since the first low-pass filter 4 is composed of a secondary one having a relatively gentle characteristic, a low-frequency signal outside the reproduction frequency band of the speaker, which is a band equal to or lower than the cutoff frequency of the first low-pass filter 4. In addition, a low-frequency signal within the reproduction frequency band of the speaker, which is a band equal to or higher than the cutoff frequency of the first low-pass filter 4, is also extracted. However, the signal level within the reproduction frequency band of the speaker is smaller than the signal level outside the reproduction frequency band of the speaker.
Therefore, when the signal level input to the harmonic generation means 5 is large, the low-frequency signal outside the reproduction frequency band of the speaker, which is a band below the cutoff frequency of the first low-pass filter 4, has a high signal level. Therefore, it is converted into a harmonic including the second harmonic and the third harmonic. Since the low-frequency signal in the reproduction frequency band of the speaker, which is a band equal to or higher than the cutoff frequency of the first low-pass filter 4, becomes lower in signal level as the frequency increases, the ratio of generated harmonics becomes smaller. At the same time, the ratio of the fundamental wave increases. Since the phase inverting means 3 compensates for the phase lag of the first low-pass filter 4, there is no phase lag of the fundamental wave.
When the signal level input to the harmonic generation means 5 is small, the harmonics pass without being generated regardless of the band, but the signal level has a frequency according to the attenuation characteristic of the first low-pass filter 4. As the value increases, it decreases.

  The signal output from the harmonic generation means 5 is input to the second low-pass filter 10, unnecessary harmonics are cut, and harmonics in a necessary band are extracted. The cutoff frequency of the second low-pass filter 10 is the cutoff frequency of the first low-pass filter 4 in order to extract up to the third harmonic of the low-frequency signal extracted by the first low-pass filter 4. Set to about 3 times the frequency. In order not to increase the circuit scale, a second order low-pass filter 10 is used.

  Due to the second low-pass filter 10, there is no phase delay in the pass band, and the phase is delayed by 180 ° in the cutoff band. When the phase change by the phase inverting means 3 and the first low-pass filter 4 is included, the phase is 180 ° in the low band outside the reproduction frequency band of the speaker, which is a band below the cutoff frequency of the first low-pass filter 4. Then, there is no phase lag in the low range within the reproduction frequency band of the speaker, which is the band between the cutoff frequency of the first low-pass filter 4 and the cutoff frequency of the second low-pass filter 10. The phase is delayed by 180 ° in the middle and low frequencies within the reproduction frequency band of the speaker, which is a band higher than the cut-off frequency of the low-pass filter 10.

  When the signal level input to the harmonic addition unit 1 is large, the low-frequency signal outside the reproduction frequency band of the speaker, which is a band equal to or lower than the cutoff frequency of the first low-pass filter 4, is the second harmonic. It is converted into a harmonic including the third harmonic. A low-frequency signal within the reproduction frequency band of the speaker, which is a band between the cutoff frequency of the first low-pass filter 4 and the cutoff frequency of the second low-pass filter 10, is generated as the frequency increases. As the ratio of harmonics decreases, the ratio of fundamental waves increases. There is no phase delay of the fundamental wave. The mid-low band signal in the reproduction frequency band of the speaker, which is a band equal to or higher than the cutoff frequency of the second low-pass filter 10, has a low signal level and a phase that is delayed by 180 °.

  When the signal level input to the harmonic adding unit 1 is small, a low-pass signal outside the reproduction frequency band of the speaker, which is a band equal to or lower than the cutoff frequency of the first low-pass filter 4, is advanced by 180 ° in phase. To do. A low-frequency signal in the reproduction frequency band of the speaker, which is a band between the cutoff frequency of the first low-pass filter 4 and the cutoff frequency of the second low-pass filter 10, has a low signal level and a phase delay. Passes without any fundamental wave. The mid-low band signal in the reproduction frequency band of the speaker, which is a band equal to or higher than the cutoff frequency of the second low-pass filter 10, further passes through the signal level with a phase delay of 180 °.

  The signal output from the second low-pass filter 10 which is the final stage of the harmonic adding unit 1 is input to the first adding means 11 and 12, and the left and right signals input to the input terminals T1 and T2, respectively. Is added.

  When the input signal level is high, the outputs of the first adding means 11 and 12 are low-order signals outside the reproduction frequency band of the speaker, which are bands below the cutoff frequency of the first low-pass filter 4. Harmonics including harmonics and third harmonics are added. The low-frequency signal in the reproduction frequency band of the speaker, which is a band between the cutoff frequency of the first low-pass filter 4 and the cutoff frequency of the second low-pass filter 10, is the second harmonic and the third harmonic. The harmonics including the second harmonic are added a little and the signal level of the fundamental wave is slightly increased and output. The mid-low range signal in the reproduction frequency band of the speaker, which is a band higher than the cutoff frequency of the second low pass filter 10, is output from the harmonic adding unit 1 with a phase delayed by 180 °, but the signal level is small. The signals output from the first adding means 11 and 12 are hardly affected.

  When the input signal level is low, the outputs of the first adding means 11 and 12 are low-frequency signals outside the reproduction frequency band of the speaker, which are bands below the cut-off frequency of the first low-pass filter 4. Since the phase is advanced by 180 ° from the unit 1, the signal level is reduced and output. A low-frequency signal in the reproduction frequency band of the speaker, which is a band between the cutoff frequency of the first low-pass filter 4 and the cutoff frequency of the second low-pass filter 10, is output from the harmonic addition unit 1. Since the signal is output without delay, the signal level is increased and output. The mid-low range signal in the reproduction frequency band of the speaker, which is a band higher than the cutoff frequency of the second low pass filter 10, is output from the harmonic adding unit 1 with a phase delayed by 180 °, but the signal level is small. The signals output from the first adding means 11 and 12 are hardly affected.

  In this way, when the input signal level is high with respect to the audio signal input to the apparatus, the harmonics including the second and third harmonics of the low-frequency signal outside the reproduction frequency band of the speaker. When a wave is added and the input signal level is low, the low-frequency gain increases. Therefore, the low-frequency response of the speaker is compensated for without lowering the size of the speaker and the power amplifier that drives it, thereby reducing the low-frequency sound. It can be strengthened.

(Embodiment 2)
FIG. 9 is a block diagram of the bass enhancement device according to Embodiment 2 of the present invention.

  Hereinafter, a description will be given with reference to FIG. The description of the same parts as in the first embodiment will be omitted, but the volume adjusting means 13 and 14, the added amount adjusting means 15, the first filter characteristic switching means 16 and the second filter characteristic in the first embodiment. The switching means 17, the control means 18, the sound discrimination means 19, and the reproduction means 20 are added.

First, the left and right audio signals input to the bass enhancement device are input to the volume adjusting means 13 and 14 and the volume is adjusted. The volume control means 13 and 14 are constituted by electronic volumes. The control unit 18 instructs the volume adjustment units 13 and 14 to adjust the volume.
As described in the first embodiment, the bass enhancement device of the present invention increases the low-frequency gain when the input signal level is small, but the volume adjustment means 13 and 14 are replaced with the second addition means 2 and the first addition means 2. By arranging it in front of the adding means 11 and 12, the effect of increasing the low-frequency gain at the time of a small sound volume is increased.

  The left and right audio signals output from the volume control means 13 and 14 are branched into two signals: a signal input to the first adding means 11 and 12 and a signal input to the harmonic wave adding unit 1, respectively.

  The harmonic addition unit 1 includes a second addition unit 2, a phase inversion unit 3, a first low-pass filter 4, a harmonic generation unit 5, a second low-pass filter 10, an addition amount adjustment unit 15, a first Filter characteristic switching means 16 and second filter characteristic switching means 17.

The additional amount adjusting means 15 adjusts the magnitude of the signal output from the second low-pass filter 10 and is composed of an electronic volume. The control unit 18 instructs the additional amount adjusting unit 15 to adjust the additional amount.
The first filter characteristic switching means 16 is for switching the pass characteristic of the first low-pass filter 4 and is configured to switch the constant of the first low-pass filter 4. The control means 18 instructs the first filter characteristic switching means 16 to switch the filter characteristics.

The second filter characteristic switching means 17 is for switching the pass characteristic of the second low-pass filter 10 and is configured to switch the constant of the second low-pass filter 10. The control means 18 instructs the second filter characteristic switching means 17 to switch the filter characteristics.
Here, the description has been made assuming that one control means is provided, but control may be performed by individual control means.

  In order to perform an optimal correction according to the type of audio signal input to the apparatus, the audio discriminating means 19 for discriminating the number of channels of audio recorded in the medium on which the input audio is recorded and the medium is provided. Information about the type of sound is transmitted to the control means 18. The sound discriminating means 19 is a medium on which sound is recorded, that is, a CD or DVD video, based on recognition information such as TOC information of the medium that is reproduced by the reproducing means 20 and inputted to the apparatus. Whether it is DVD audio or not is discriminated. Also, the number of audio channels included in the medium, that is, whether only a 2-channel sound source or a 5.1-channel sound source is included is determined. Then, the result is transmitted to the control means 18.

  In general, movie audio signals contain more signals of lower frequencies than music signals, and a stronger bass enhancement effect is required. Therefore, based on the information related to the type of sound transmitted from the sound discrimination means 19, the control means 18 has a DVD video as the medium on which the sound is recorded, and the medium includes a 5.1 channel sound source. If so, the first filter switching means 16 and the second filter are set so that the cutoff frequencies of the first low-pass filter 4 and the second low-pass filter 10 are set lower than in other cases. The switching unit 17 is instructed, and the additional amount adjusting unit 15 is instructed to further increase the additional amount. The instruction to the first filter switching unit 16 and the second filter switching unit 17 and the instruction to the additional amount adjusting unit 15 to increase the additional amount may be performed either or both at the same time. .

  This makes it possible to automatically perform optimum correction according to the type of audio signal input to the apparatus.

(Embodiment 3)
FIG. 10 is a circuit diagram of the harmonic generation means 5 of the bass enhancement device according to Embodiment 3 of the present invention, FIG. 11 is an input / output characteristic diagram of the nonlinear arithmetic means 6, and FIG. 12 is also the harmonic generation means 5. Similarly, FIG. 13 is a spectrum diagram when a single sine wave is input to the harmonic generation means 5. Note that the basic configuration of the bass enhancement device is the same as that of FIG. 1 used in the first embodiment.

  Hereinafter, description will be made with reference to FIGS. 1 and 10 to 13. The harmonic generation means 5 shown in FIG. 10 inserts a resistor R32 into the feedback section of the pre-stage amplifier IC31 of the full-wave rectifier circuit using the diodes D31 and D32 to shift the turn-around point of the full-wave rectifier and The value constants are set so that the positive and negative gains are different. Note that the coefficients of the first coefficient unit 7 and the second coefficient unit 8 are set by the gain inside the linear arithmetic means 9. R31 to R35 are resistors. The linear calculation means 9 itself composed of the IC 32 and the resistors R36 and R37 is the same as that of 9 in FIG.

  FIG. 11 is an input / output characteristic diagram of the nonlinear arithmetic means 6, but is different from FIG. 4 which is an input / output characteristic chart of the nonlinear arithmetic means 6 in the first embodiment. In the first embodiment, the amplitude is suppressed with respect to a negative input voltage of a certain voltage or less. In the third embodiment, the amplitude is expanded with respect to a negative input voltage of a certain voltage or less. is there.

  Therefore, in FIG. 10, unlike FIG. 6, the input to the harmonic generation means 5 is connected to the non-inverting input side of the IC 32 of the linear calculation means 9, and the output of the nonlinear calculation means 6 is connected to the inverting input side. The latter is subtracted from the former to obtain the characteristics shown in FIG.

  FIG. 12 is an input / output characteristic diagram of the harmonic generation means 5, which is similar to FIG. 7 which is an input / output characteristic diagram of the harmonic generation means 5 in the first embodiment. In other words, the input / output characteristics pass over the origin, have break points at at least one place other than the origin, are asymmetric at the origin, and have a linear characteristic when the absolute value of the input signal level is below a certain value. When the absolute value of the signal level is greater than or equal to a certain value, the input / output characteristic has a characteristic that turns back in the direction intersecting the input axis at the time of negative input.

  FIG. 13 is a spectrum diagram when a single sine wave is input to the harmonic generation means 5, but FIG. 8 is a spectrum when a single sine wave is input to the harmonic generation means 5 in the first embodiment. Similarly, the signal level of the fundamental wave is suppressed, and harmonics including the second harmonic and the third harmonic are generated. Note that the signal level input to the harmonic generation means 5 is adjusted higher than in the first embodiment.

  Thus, according to the present embodiment, regardless of the input / output characteristics of the nonlinear arithmetic means 6, the input / output characteristics of the harmonic generation means 5 pass over the origin and break points are formed at least at one place other than the origin. If the absolute value of the input signal level is below a certain value, it has a linear characteristic, and if the absolute value of the input signal level is above a certain value, the input / output characteristics are negative input and the input / output characteristics are If the signal has a characteristic of turning back in the direction intersecting with, the signal level of the fundamental wave is small, and harmonics including the second and third harmonics can be generated.

  In each of the above embodiments, the position of the phase inverting means 3 is not limited to the illustrated part, and may be arranged at any part in the harmonic adding part. Or you may arrange | position in the front | former stage of the 1st addition means 11 and 12. FIG.

  Further, the action of the phase inverting means 3 and the action of the first adding means 11 and 12 may be combined, and the first adding means 11 and 12 may be constituted by subtracting means. That is, in each of the above embodiments, the action of two or more means may be realized by one means, or the action of one means may be realized by two or more means.

  Furthermore, when the input / output characteristics pass over the origin, there are break points at least one place other than the origin, the origin is asymmetric, and the input signal level has a linear characteristic when the absolute value is below a certain value. If the absolute value of the signal level is equal to or greater than a certain value, the circuit is limited to the circuit illustrated here as long as the input / output characteristics can be folded back in the direction intersecting the input axis at the time of negative input. is not.

  The bass enhancement device according to the present invention is used to compensate for a decrease in low-frequency characteristics from a speaker and enhance a bass feeling in a small stereo, a television, etc., in which it is difficult to increase the size of a speaker and a power amplifier that drives the speaker. Applicable to.

Block diagram of bass enhancement device in Embodiments 1 and 3 of the present invention 1 is a circuit diagram of an inverting addition amplifier according to Embodiment 1 of the present invention. Circuit diagram of non-linear operation means in Embodiment 1 of the present invention Input / output characteristics diagram of nonlinear arithmetic means in Embodiment 1 of the present invention Spectrum diagram when a single sine wave is input to the nonlinear arithmetic means in Embodiment 1 of the present invention Circuit diagram of harmonic generation means in Embodiment 1 of the present invention Input / output characteristic diagram of harmonic generation means in Embodiment 1 of the present invention Spectrum diagram when a single sine wave is input to the harmonic generation means in Embodiment 1 of the present invention Block diagram of bass enhancement device in Embodiment 2 of the present invention Circuit diagram of harmonic generation means in Embodiment 3 of the present invention Input / output characteristic diagram of nonlinear arithmetic means in Embodiment 3 of the present invention Input / output characteristic diagram of harmonic generation means in Embodiment 3 of the present invention Spectrum diagram when a single sine wave is input to the harmonic generation means in Embodiment 3 of the present invention Conceptual diagram of harmonic addition of the present invention Block diagram of a conventional bass booster

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Harmonic addition part 2 2nd addition means 3 Phase inversion means 4 1st low-pass filter 5 Harmonic generation means 6 Nonlinear calculation means 7 1st coefficient multiplier 8 2nd coefficient multiplier 9 Linear calculation means 10 1st Two low-pass filters 11, 12 First addition means 13, 14 Volume adjustment means 15 Amount adjustment means 16 First filter characteristic switching means 17 Second filter characteristic switching means 18 Control means 19 Audio discrimination means 20 Reproduction Means 31 Harmonic addition unit 32 Second addition means 33 First low pass filter 34 Harmonic generation means 35 Full wave rectifier 36 Second low pass filter 37, 38 First addition means

Claims (10)

A first low-pass filter that extracts a low-frequency component of a signal input to the device;
Harmonic generation means for generating harmonics of a low-frequency signal output from the first low-pass filter;
A second low-pass filter for extracting a low-frequency component of the signal output from the harmonic generation means;
First adding means for adding the signal output from the second low-pass filter to the input audio signal and outputting the signal from the device;
Further, the harmonic generation means includes a first coefficient multiplier that multiplies a low-frequency signal output from the first low-pass filter by a predetermined coefficient, and a low-frequency output from the first low-pass filter. A non-linear operation means for performing non-linear operation on the signal, a second coefficient unit for multiplying the signal output from the non-linear calculation means by a predetermined coefficient, the signal output from the first coefficient unit, and the second A linear operation for performing addition or subtraction processing on the signal output from the coefficient unit and attenuating the low-frequency signal output from the first low-pass filter from the signal output from the nonlinear arithmetic means Means and
The non-linear operation means has an input / output characteristic that passes over the origin, has break points at at least one place other than the origin, and is asymmetric with respect to the origin. Second addition means for adding a plurality of channels of audio signals input to the apparatus;
A first low-pass filter for extracting a low-frequency component of the signal output from the second adding means;
Harmonic generation means for generating harmonics of a low-frequency signal output from the first low-pass filter;
A second low-pass filter for extracting a low-frequency component of the signal output from the harmonic generation means;
First adding means for adding the signal output from the second low-pass filter to the input audio signal and outputting the signal from the device;
Further, the harmonic generation means includes a first coefficient multiplier that multiplies a low-frequency signal output from the first low-pass filter by a predetermined coefficient, and a low-frequency output from the first low-pass filter. A non-linear operation means for performing non-linear operation on the signal, a second coefficient unit for multiplying the signal output from the non-linear calculation means by a predetermined coefficient, the signal output from the first coefficient unit, and the second A linear operation for performing addition or subtraction processing on the signal output from the coefficient unit and attenuating the low-frequency signal output from the first low-pass filter from the signal output from the nonlinear arithmetic means Means and
The non-linear operation means has an input / output characteristic that passes over the origin, has break points at at least one place other than the origin, and is asymmetric with respect to the origin. The bass enhancement device according to claim 1 or 2, wherein the non-linear operation means comprises a positive / negative asymmetric limiter circuit. A first low-pass filter that extracts a low-frequency component of a signal input to the device;
Harmonic generation means for generating harmonics of a low-frequency signal output from the first low-pass filter;
A second low-pass filter for extracting a low-frequency component of the signal output from the harmonic generation means;
First adding means for adding the signal output from the second low-pass filter to the input audio signal and outputting the signal from the device;
The harmonic generation means has input / output characteristics passing over the origin, having break points at least one place other than the origin, and being asymmetric at the origin,
When the absolute value of the input signal level is below a certain value, it has a linear characteristic,
A bass enhancement device characterized in that when the absolute value of the input signal level is equal to or greater than a certain value, the input / output characteristics are turned back in a direction intersecting the input axis at least during positive input or negative input. Second addition means for adding a plurality of channels of audio signals input to the apparatus;
A first low-pass filter for extracting a low-frequency component of the signal output from the second adding means;
Harmonic generation means for generating harmonics of a low-frequency signal output from the first low-pass filter;
A second low-pass filter for extracting a low-frequency component of the signal output from the harmonic generation means;
First adding means for adding the signal output from the second low-pass filter to the input audio signal and outputting the signal from the device;
The harmonic generation means has input / output characteristics passing over the origin, having break points at least one place other than the origin, and being asymmetric at the origin,
When the absolute value of the input signal level is below a certain value, it has a linear characteristic,
A bass enhancement device characterized in that when the absolute value of the input signal level is equal to or greater than a certain value, the input / output characteristics are turned back in a direction intersecting the input axis at least during positive input or negative input. A phase inversion unit for inverting the phase of the harmonic addition unit including the second addition unit, the first low-pass filter, the harmonic generation unit, and the second low-pass filter; The bass enhancing device according to any one of claims 1 to 5, characterized in that: The bass enhancement device according to claim 6, wherein the first low-pass filter is a secondary filter. The volume adjusting means for adjusting the volume of the audio signals of a plurality of channels input to the apparatus is provided in a stage preceding the first adding means and the second adding means. The bass enhancement device according to any one of the above. First filter characteristic switching means for switching a pass characteristic of the first low-pass filter;
Control means for instructing characteristic switching to the first filter characteristic switching means;
Second filter characteristic switching means for switching a pass characteristic of the second low-pass filter;
Control means for instructing characteristic switching to the second filter characteristic switching means;
Additional amount adjusting means for adjusting the volume of the signal output from the harmonic adding unit;
Control means for instructing addition amount adjustment to the addition amount adjustment means;
Further comprising a medium in which the input sound is recorded and a sound determination means for determining the number of channels of the sound included in the medium;
At least one of the pass characteristic of the first low-pass filter, the pass characteristic of the second low-pass filter, or the additional amount of the additional amount adjusting unit is set according to the type of input sound. The bass enhancement device according to any one of claims 1 to 8, wherein the bass enhancement device is configured to be automatically switched. When the medium on which the input sound is recorded is DVD video and the medium includes a 5.1 channel sound source, the cutoff frequency of the first low-pass filter and The bass enhancement device according to claim 9, wherein the cutoff frequency of the second low-pass filter is switched to a low frequency, or the additional amount of the additional amount adjusting means is increased.

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