JP2012147179A - Bass intensifier, bass intensifying method, and computer program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bass intensifier capable of intensifying bass at a small sound volume and capable of preventing audibility from being deteriorated by an increase in sound volume.SOLUTION: A bass intensifier 100 for intensifying a low-pitched sound component of a voice reproduced from a speaker comprises: a fundamental wave extraction circuit 4 that extracts a fundamental wave band component as a frequency component equal to/lower than a reproduction frequency band of the speaker, from an input voice signal input into an input terminal 1; a sound volume detection circuit 11 that detects a sound volume reproduced by the speaker and that generates a control signal depending on the magnitude of the reproduced sound volume; and a harmonic generation circuit 5 that generates a harmonic content of the fundamental wave band component on the basis of the control signal.

Description

  The present invention relates to a bass enhancement device capable of boosting bass, a bass enhancement method, and a computer program.

  Conventional audio reproduction devices have been implemented with loudness control that compensates for the audible balance at low volumes. This is based on the human auditory property that the bass and treble are generally harder to hear when the volume is low. The loudness control that boosts and corrects the low and high frequencies in conjunction with the decrease in volume makes it possible to make the frequency characteristics on the auditory side more flat.

  In particular, as a method of enhancing the bass, there is a method of using a pseudo bass effect in which a bass tone is amplified by adding a harmonic distortion due to a nonlinear distortion to a fundamental wave in a bass range. When the volume is low, there is no problem even if the bass is increased by the pseudo bass effect. However, when the volume is increased, the harmonic distortion component due to the pseudo bass effect becomes uncomfortable in terms of hearing. In order to prevent deterioration of the audibility due to harmonic distortion, there is a proposal for controlling the amount of harmonic distortion by comparing the levels of low and high frequencies (see Patent Document 1).

JP 2009-244650 A

  However, Patent Document 1 is a method based on the level difference between the low sound range and the high sound range, and does not necessarily control the pseudo bass effect based on the volume level.

  An object of the present invention is to provide a bass enhancement device, a bass enhancement method, and a computer program that can perform bass enhancement at a low volume level and can prevent a deterioration in audibility associated with the volume increase.

  According to the first aspect of the present invention, in the bass enhancement device that enhances the bass component of the sound reproduced from the speaker, the basic frequency component is a frequency component equal to or lower than the reproduction frequency band of the speaker from the input sound signal input to the input terminal. A fundamental wave extraction circuit that extracts a waveband component, a volume detection circuit that detects a volume reproduced by a speaker and generates a control signal according to the volume of the reproduction volume, and a fundamental band component based on the control signal There is provided a bass enhancement device including a harmonic generation circuit that generates a higher harmonic component.

  According to the second aspect of the present invention, in the bass enhancement method for enhancing the bass component of the sound reproduced from the speaker, the frequency component is equal to or lower than the reproduction frequency band of the speaker from the input sound signal input to the input terminal. A fundamental wave extraction step for extracting a fundamental wave band component, a volume detection step for detecting a volume reproduced by a speaker and generating a control signal according to the magnitude of the reproduction volume, and a fundamental band based on the control signal A bass enhancement method is provided that includes a harmonic generation step for generating a harmonic component of the component.

  According to the third aspect of the present invention, a frequency component equal to or lower than the reproduction frequency band of the speaker is input from the input audio signal input to the input terminal to the computer of the bass enhancement device that enhances the bass component of the audio reproduced from the speaker. A fundamental wave extraction step for extracting a fundamental wave band component, a volume detection step for detecting a volume reproduced by a speaker, and generating a control signal corresponding to the magnitude of the reproduction volume, and a basis based on the control signal A computer program for executing a harmonic generation step for generating a harmonic component of a waveband component is provided.

  According to the present invention, it is possible to provide a bass enhancement device, a bass enhancement method, and a computer program that can perform bass enhancement at a low volume level and can prevent deterioration of the audibility associated with the volume increase.

It is a block diagram which shows an example of the bass enhancing device which concerns on embodiment of this invention. It is a figure which shows an example of the relationship between a speaker reproduction | regeneration characteristic and a fundamental band. It is a figure which shows the other example of the relationship between a speaker reproduction characteristic and a fundamental band. It is a figure which shows an example of the relationship between the volume of the bass enhancement device which concerns on embodiment of this invention, and a harmonic generation amount. It is a figure which shows an example of the nonlinear process of the bass enhancing device which concerns on embodiment of this invention. It is a figure which shows an example of the input waveform used for description of the nonlinear process of the bass enhancement device which concerns on embodiment of this invention. It is a figure which shows an example of the output waveform used for description of the nonlinear process of the bass enhancement device which concerns on embodiment of this invention. It is a figure which shows an example of the high frequency generation circuit of the bass enhancement device which concerns on embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and the configuration of the apparatus and system is different from the actual one. Therefore, a specific configuration should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different structures and the like are included between the drawings.

  The following embodiments of the present invention exemplify apparatuses and methods for embodying the technical idea of the present invention. The technical idea of the present invention is based on the material and shape of component parts. The structure, arrangement, etc. are not specified below. The technical idea of the present invention can be variously modified within the technical scope described in the claims.

  As shown in FIG. 1, a bass enhancement device 100 according to an embodiment of the present invention includes a delay circuit 3, a fundamental wave extraction circuit 4, a harmonic generation circuit 5, a bandpass filter 6, amplification circuits 7 and 8, and an addition circuit. 9. A volume control volume 10 and a volume detection circuit 11 are provided. The inputs of the delay circuit 3 and the fundamental wave extraction circuit 4 are connected to the input terminal 1. The output of the delay circuit 3 is connected to the input of the amplifier circuit 7. The output of the fundamental wave extraction circuit 4 is connected to the input of the harmonic generation circuit 5. The output of the harmonic generation circuit 5 is connected to the input of the bandpass filter 6. The output of the band pass filter 6 is connected to the input of the amplifier circuit 8. The outputs of the amplifier circuits 7 and 8 are connected to the input of the adder circuit 9, respectively. The output of the adder circuit 9 is connected to the output terminal 2. The volume detection circuit 11 is connected to the volume adjustment volume 10 and the harmonic generation circuit 5. In addition, you may make it the structure that another functional block enters between each part as needed.

  The audio signal is input from the input terminal 1 to the bass enhancement device 100. The delay circuit 3 compensates for a processing time delay caused by the fundamental wave extraction circuit 4 and the harmonic generation circuit 5 with respect to the input audio signal. That is, the audio signal is delayed by the processing time by the fundamental wave extraction circuit 4, the harmonic generation circuit 5, and the like. Then, the main audio signal subjected to delay compensation is output to the amplifier circuit 7.

  The fundamental wave extraction circuit 4 has a fundamental wave band component in a frequency band equal to or lower than a reproduction frequency band of a speaker (not shown) used in an audio reproduction apparatus that reproduces audio whose bass is enhanced by the bass enhancement apparatus 100 of the present embodiment. Are extracted from the input audio signal. For example, as shown in FIG. 2, in the speaker reproduction characteristics, a range between a cutoff frequency fc near the lowest resonance frequency f0 and a frequency fc / 2 that is ½ of the cutoff frequency fc is set as a fundamental band. In this case, as the fundamental wave extraction circuit 4, a band pass filter that passes the frequency band in the range of the frequency fc / 2 to fc may be used. The cut-off frequency on the low band side of the band-pass filter is set to fc / 2 because the frequency component of the frequency fc / 2 or less is a frequency band fc / 2 that is difficult to reproduce with a speaker even for the harmonic component. This is because there is a possibility of entering fc. The extracted fundamental band component is output to the harmonic generation circuit 5.

  It should be noted that in the bass enhancement device that is always used for the same speaker, the cutoff frequency fc may be determined in advance. Moreover, you may make it change according to the speaker connected using the filter which can change the cutoff frequency fc. As described above, when the cutoff frequency fc is changed according to the connected speaker, a control unit (not shown) acquires information on the lowest resonance frequency f0 of the speaker, and the cutoff frequency fc is set according to the information. Set.

  In addition, as shown in FIG. 3, it is good also considering all the frequency bands below the cut-off frequency fc of a speaker as a fundamental wave band. Even so, the bass enhancement effect can be obtained. This is effective when it is difficult to design a band-pass filter having a narrow band in a low frequency range.

  The volume adjustment volume 10 adjusts the volume reproduced by the speaker. The volume detection circuit 11 detects the position of the volume adjustment volume 10 to generate a control signal corresponding to the volume of the reproduction volume by the speaker. Note that a control signal corresponding to the level of the reproduction volume of the speaker may be generated by detecting the level of the audio signal without detecting the position of the volume control volume 10. The harmonic generation circuit 5 generates a harmonic component of the fundamental band component extracted by the fundamental wave extraction circuit 4 based on the control signal generated by the volume detection circuit 11.

  The bandpass filter 6 removes unnecessary frequency components from the harmonic components output from the harmonic generation circuit 5 and outputs a desired harmonic component to the amplifier circuit 8. For example, a harmonic component of about 1 kHz or more does not contribute to the pseudo bass effect and adversely affects an audibly sensitive band. Further, in the nonlinear processing of the harmonic generation circuit 5, in addition to the harmonics, a low-frequency fundamental wave band component is also generated secondarily. The purpose of the bandpass filter 6 is to remove such unnecessary high-frequency components and low-frequency components. The adder circuit 9 adds the main signal from the amplifier circuit 7 and the harmonic component signal from the amplifier circuit 8 and outputs the result to the output terminal 2.

  For example, as shown in FIG. 4, the sound volume detection circuit 11 generates a control signal for controlling the amount of generated harmonics according to the position of the sound volume adjustment volume. The harmonic generation circuit 5 is controlled by the control signal so that the harmonic generation amount is large at the position of the volume adjustment volume corresponding to the low volume, and the harmonic generation amount is small at the position corresponding to the large volume. Note that when the volume level increases beyond a predetermined upper limit, harmonics are perceived as distortion in the sense of hearing. In such a case, as shown in FIG. 4, the upper limit Th of the position of the volume control volume is set corresponding to the upper limit of the volume level, and the harmonic generation amount is controlled to be 0 above the upper limit Th. To do.

  As the harmonic generation circuit 5, a non-linear processing circuit capable of generating harmonics such as a full-wave rectification method, a power method, and a zero cross method is used. The control signal generated by the volume detection circuit 11 controls the nonlinear processing parameters of the harmonic generation circuit 5.

  FIG. 5 shows changes in the amplitude of the input waveform and output waveform of the harmonic generation circuit 5. As shown in FIG. 5, when the volume level is low, the amount of harmonics generated by the harmonic generation circuit 5 is increased, and therefore, the nonlinear characteristic NA with a large amount of waveform deformation is obtained. As the volume level increases, the amount of harmonic generation decreases, so that the nonlinear characteristic NB has a smaller amount of waveform deformation than the nonlinear characteristic NA. Further, as shown in FIG. 4, at the upper limit Th or more, the high frequency generation amount is 0, and the linear characteristic NC has no waveform deformation. That is, the input / output characteristics of the harmonic generation circuit 5 become closer to linear characteristics as the volume increases.

  For example, as shown in FIG. 6, if the input reproduction signal is a sine wave, the harmonic generation circuit 5 at the low sound volume level causes harmonic distortion corresponding to the nonlinear characteristic NA as shown in FIG. A large output waveform PA is output. When the volume level is increased, the harmonic generation circuit 5 outputs an output waveform PB in which harmonic distortion is reduced corresponding to the nonlinear characteristic NB. At a high volume level corresponding to the upper limit Th or more, the harmonic generation circuit 5 outputs an output waveform PC having no harmonic distortion corresponding to the linear characteristic NC.

  In the bass enhancement device 100 according to the embodiment, the position of the volume adjustment volume is detected, and a control signal corresponding to the magnitude of the reproduction volume of the speaker is generated. When the volume is small, the amount of generated harmonics is increased, and when the volume is large, the amount of generated harmonics is reduced or set to 0 and added to the input audio signal. In this way, since the amount of the harmonic component added to the audio signal is adjusted according to the volume, it is possible to prevent the harmonic component from being perceived as distortion in the sense of hearing. Further, since the amount of generated harmonics is 0 at a large volume equal to or higher than the upper limit Th, a reproduced sound without distortion can be realized.

  In the above description, the nonlinear processing parameter of the harmonic generation circuit 5 is adjusted to control the generation amount of the harmonic component. However, the output gain of the generated harmonic component may be adjusted. For example, as shown in FIG. 8, the harmonic generation circuit 5 includes a nonlinear processing circuit 5a and an amplification circuit 5b. The nonlinear processing circuit 5 a performs nonlinear processing on the fundamental band component input from the fundamental wave extraction circuit 4 to generate a harmonic signal. The control signal generated by the volume detection circuit 11 is input to the control terminal of the amplifier circuit 5b. Based on the control signal, the amplification factor of the amplifier circuit 5b is controlled, and the intensity of the output harmonic signal can be controlled. As a result, the harmonic component to be added can be reduced as the volume increases, and the harmonic component can be reduced to 0 above the upper limit of the volume.

(Other embodiments)
Although the embodiments of the present invention have been described as described above, it should not be understood that the descriptions and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art. Accordingly, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description. For example, the present invention includes a program for causing a computer to realize the operation of each unit of each embodiment. These programs may be read from a recording medium and loaded into a computer, or may be transmitted via a communication network and loaded into a computer. Further, the present invention includes a bass enhancement method performed by each unit of each embodiment.

DESCRIPTION OF SYMBOLS 3 ... Delay circuit 4 ... Fundamental wave extraction circuit 5 ... Harmonic wave generation circuit 6 ... Band pass filter 7 ... Amplification circuit 8 ... Amplification circuit 9 ... Addition circuit 10 ... Volume control volume 11 ... Volume detection circuit 100 ... Bass booster

Claims (5)

In the bass enhancement device that enhances the bass component of the sound reproduced from the speaker,
A fundamental wave extraction circuit that extracts a fundamental wave band component that is a frequency component below the reproduction frequency band of the speaker from an input audio signal input to the input terminal;
A volume detection circuit that detects a volume reproduced by the speaker and generates a control signal according to the magnitude of the reproduction volume;
And a harmonic generation circuit that generates a harmonic component of the fundamental band component based on the control signal.   2. The bass enhancement device according to claim 1, wherein the harmonic generation circuit deforms an input waveform of the fundamental band component so that a deformation amount decreases as the reproduction volume increases.   2. The bass enhancement device according to claim 1, wherein the harmonic generation circuit generates the harmonic component so as to decrease an amplification factor as the reproduction volume is increased. In the bass enhancement method for enhancing the bass component of the sound reproduced from the speaker,
A fundamental wave extraction step of extracting a fundamental wave band component that is a frequency component equal to or lower than the reproduction frequency band of the speaker from the input audio signal input to the input terminal;
A volume detection step of detecting a volume reproduced by the speaker and generating a control signal according to the magnitude of the reproduction volume;
And a harmonic generation step of generating a harmonic component of the fundamental band component based on the control signal. To the computer of the bass enhancement device that enhances the bass component of the sound reproduced from the speaker
A fundamental wave extraction step of extracting a fundamental wave band component that is a frequency component equal to or lower than the reproduction frequency band of the speaker from the input audio signal input to the input terminal;
A volume detection step of detecting a volume reproduced by the speaker and generating a control signal according to the magnitude of the reproduction volume;
And a harmonic generation step of generating a harmonic component of the fundamental band component based on the control signal.

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