JP2012108411A - Audio signal reproduction device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that there is a case in which a DC-removed signal possibly shifts in phase since DC removal is not complete although the DC removal is performed as a DC component is also generated when an even-order harmonic signal is generated and a vibration range of a speaker diaphragm is limited to make deterioration in sound quality easy to occur, and also to solve the problem that high-order harmonics have inferior power balance between odd-order harmonics and even-order harmonics and sound quality deteriorates.SOLUTION: An odd-order harmonic signal is generated from a bass component of an audio signal, and a 90° phase shift signal is generated from the bass component, and multiplied by the odd-order harmonic signal to generate an even-order harmonic signal. A first amplitude adjustment part adjusts the amplitude of the even-order harmonic signal, and the odd-ordered harmonic signal and the amplitude-adjusted even-order harmonic signal is summed up to output a harmonic signal. A second amplitude adjustment part adjusts the amplitude of the harmonic signal, and the audio signal and the harmonic signal having the amplitude adjusted by the second amplitude adjustment part are summed up to output an output signal.

Description

  The present invention relates to an audio signal reproduction apparatus that generates a pseudo deep bass sound that makes a speaker with insufficient bass reproduction capability feel a low frequency in a band with insufficient reproduction capability in a pseudo manner.

  In recent years, many technologies have been developed to create a low-pitched sound by using a psychoacoustic feature “Missing fundamental” for a speaker with insufficient bass reproduction capability. “Missing fundamental” is an illusion that when a user listens to two or more frequencies at the same time, the difference sound is heard. For example, the following Patent Document 1 discloses a pseudo deep bass generating device using the psychoacoustic feature “Missing fundamental”.

In the pseudo deep bass generating device according to Patent Document 1, a harmonic component signal is generated from a bass component signal having a lowest resonance frequency f ₀ or less of a speaker, and the harmonic component signal is added to an audio signal that is an input signal. Even if there is no bass component below the lowest resonance frequency f ₀ of the speaker, the illusion that the bass component can be heard by the harmonic component signal.

  In the pseudo heavy bass generator, in the configuration of FIG. 11, a bass component signal extracted from an audio signal as an input signal is input to a square wave signal generator 21 to generate a square wave signal. The square wave signal generated by the square wave signal generation unit 21 is multiplied by the bass component signal extracted from the audio signal to generate an even-order harmonic component signal. Further, the even-order harmonic component signal generated by the multiplier 22 and the bass component signal are multiplied by the multiplier 23 to generate an odd-order harmonic component signal, and the odd-order harmonic component signal and the multiplier 22 A harmonic component signal is generated by adding the generated even-order harmonic component signals by the adder 24.

JP 2009-44655 A

The conventional pseudo deep bass generating device also generates a DC component when generating an even-order harmonic component signal. FIG. 12 shows frequency characteristics of a bass component signal (dotted line, 100 Hz sine wave), odd-order harmonic component signal (solid line), and even-order harmonic component signal (chain line). From FIG. 12, it can be seen that the even-order harmonic component signal is composed of DC components and even-order harmonic components (200 Hz, 400 Hz, 600 Hz,...) Of the bass component signal. Therefore, there is a problem that the diaphragm of the speaker is in the front (or rear) state, the vibration range of the diaphragm of the speaker is limited, sound is distorted, and sound quality is likely to deteriorate. In view of this, conventional pseudo heavy bass generators remove DC components that cause deterioration in sound quality. There are methods to remove the DC component, such as using the average value of even-order harmonic component signals or a high-pass filter (HPF), but depending on the band of the bass component extracted from the audio signal, it is not possible to completely remove the DC component. In some cases, the phase of the signal after the DC component removal is out of phase. Further, the generated even-order harmonic component signal is composed of harmonic components having a phase shift of 90 degrees, and the higher-order harmonic component is compared with the odd-order harmonic component (solid line in FIG. 12). Since the power attenuation amount of the even-order harmonic component (chain line in FIG. 12) is small and the power balance is bad, the sound quality is deteriorated.
The present invention was made to solve the above-described problems, and when generating even-order harmonic component signals, DC components that degrade sound quality and harmonic components that are 90 degrees out of phase are generated at all. The purpose is not to.

The audio signal reproducing device according to the present invention is
A bass component extraction unit that extracts a bass component signal from an audio signal that is an input signal;
An odd harmonic generation unit that generates an odd harmonic component signal from the bass component signal from the bass component extraction unit;
Similarly, a 90 degree phase conversion unit that generates a 90 degree phase shift signal from the bass component signal from the bass component extraction unit,
Even-order harmonic multiplier and even-order harmonics that generate an even-order harmonic component signal by multiplying the 90-degree phase shift signal of the 90-degree phase conversion unit and the odd-order harmonic component signal of the odd-order harmonic generation unit A first amplitude adjuster for adjusting the amplitude of the even harmonic component signal of the multiplier;
A harmonic adder that adds the odd-order harmonic component signal from the odd-order harmonic generation unit and the even-order harmonic component signal amplitude-adjusted by the first amplitude adjustment unit and outputs a harmonic component signal;
A second amplitude adjuster for adjusting the amplitude of the harmonic component signal of the harmonic adder;
An output generation adder that outputs an output signal by adding the audio signal that is an input signal and the harmonic component signal that is amplitude-adjusted by the second amplitude adjustment unit is provided.

  According to the audio signal reproducing device of the present invention, the odd-order harmonic component signal is generated by multiplying the full-wave rectified signal and the bass component signal output from the full-wave rectifier in the odd-order harmonic component signal multiplier, In addition, the odd harmonic component signal generated from the odd harmonic component signal multiplier and the bass component signal generated by the 90 degree phase conversion unit are shifted by 90 degrees in the even harmonic component signal multiplier. Since the even-order harmonic component signal having no DC component and no phase shift is generated by multiplying the phase-shift signal, a high-quality harmonic component without deterioration in sound quality can be generated. In addition, since the amplitude adjustment unit multiplies the gain α in addition to the reciprocal of the amplitude value A, the ratio of the harmonic component signal added to the input signal changes, and the low-frequency effect that is felt when the output signal is played back by a speaker Can be changed.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows the audio signal reproducing | regenerating apparatus by Embodiment 1 of this invention. It is a block diagram of the odd-order harmonic generation part in a harmonic generation part. FIG. 3 is a frequency characteristic diagram of a bass component signal (dotted line, 100 Hz sine wave) and a full-wave rectified signal (solid line) according to the first embodiment. FIG. 5 is a frequency characteristic diagram of a full-wave rectified signal (solid line) and an odd-order harmonic component signal (dotted line) according to the first embodiment. FIG. 6 is a frequency characteristic diagram of odd-order harmonic component signals (dotted lines) and even-order harmonic component signals (solid lines) according to the first embodiment. FIG. 3 is a frequency characteristic diagram of an odd-order harmonic component signal (dotted line) and an even-order harmonic component signal (solid line) whose amplitude is adjusted according to the first embodiment. FIG. 4 is a frequency characteristic diagram of a bass component signal (dotted line) and an amplitude-adjusted harmonic component signal (solid line) according to the first embodiment. It is a block diagram of the harmonic production | generation part of the audio signal reproducing | regenerating apparatus by Embodiment 2 of this invention. It is a block diagram which shows the harmonic generation part of the audio signal reproducing | regenerating apparatus by Embodiment 3 of this invention. It is a block diagram of the harmonic production | generation part of the audio signal reproducing | regenerating apparatus by Embodiment 4 of this invention. It is a block diagram of the conventional pseudo deep bass production | generation apparatus. It is a frequency characteristic diagram of a bass component signal, an odd-order harmonic component signal, and an even-order harmonic component signal in a conventional pseudo heavy bass generator.

Embodiment 1 FIG.
1 is a block diagram showing an audio signal reproducing apparatus according to Embodiment 1 of the present invention. In FIG. 1, an audio signal reproduction apparatus includes a bass component extraction unit 1 that extracts a bass component signal from an input signal that is an audio signal, a harmonic generation unit 2 that generates a harmonic component signal, and an output generation addition that generates an output signal. It is composed of vessel 3.
The harmonic generation unit 2 includes an odd-order harmonic generation unit 4 that generates an odd-order harmonic component signal, a 90-degree phase conversion unit 5 that generates a 90-degree phase shift signal, and an even-order harmonic component signal that generates an even-order harmonic component signal. Wave multiplier 6, first amplitude adjustment unit 7 that adjusts the amplitude of the even-order harmonic component signal, harmonic adder 8 that generates the harmonic component signal, and second amplitude that adjusts the amplitude of the harmonic component signal The adjustment unit 9 is configured.
FIG. 2 is a configuration diagram of the odd-order harmonic generation unit 4 in the harmonic generation unit 2. In FIG. 2, the odd-order harmonic generation unit 4 includes a full-wave rectification unit 10 that generates a full-wave rectification signal and an odd-order harmonic multiplier 11 that generates an odd-order harmonic component signal.

Next, the operation will be described.
When an input signal, which is an audio signal, is input, the bass component signal extraction unit 1 extracts a bass component signal composed of bass components having a resonance frequency f ₀ or less of the speaker from the input signal, and the harmonic component signal is a harmonic. Output to generation unit 2.
For example, when the lowest resonance frequency f ₀ of the speaker is 100 Hz, a bass component signal consisting of bass components of 100 Hz or less is extracted.
Here, the bass component signal extracted from the bass component extraction unit 1 will be described as being a sine wave Asinωt (A: amplitude value, ω: angular frequency, t: time).
The harmonic generation unit 2 distributes the bass component signal output from the bass component extraction unit 1 to the odd-order harmonic generation unit 4 and the 90-degree phase conversion unit 5, and generates a harmonic component signal of the bass component signal. The wave component signal is output to the output generation adder 3.

The output generation adder 3 adds the harmonic component signal output from the harmonic component unit 2 to the input signal that is an audio signal, and outputs the result as an output signal.
When the bass component signal is input, the odd-order harmonic generation unit 4 outputs the full-wave rectification unit 10 and the odd-order harmonic multiplier 11.
The full-wave rectification unit 10 generates a full-wave rectification signal that takes the absolute value of the amplitude value of the signal from the input bass component signal, and outputs the full-wave rectification signal to the odd-order harmonic multiplier 11.
Here, the full-wave rectified signal output from the full-wave rectifying unit 10 can be expressed as in Expression (1).

From equation (1), it can be seen that the full-wave rectified signal is composed of a DC component (solid line) and an even-order harmonic component (dotted line).
FIG. 3 shows the frequency characteristics of the bass component signal (dotted line, 100 Hz sine wave) and the full-wave rectified signal (solid line). As can be seen from FIG. 3, the full-wave rectified signal generates even-order harmonic components (200 Hz, 400 Hz, 600 Hz,...) Of the DC component and the bass component signal.
The odd-order harmonic multiplier 11 multiplies the low-frequency component signal by the full-wave rectified signal output from the full-wave rectifier 10, and generates the resulting odd-order harmonic component signal as the even-order harmonic multiplier 6 and Output to harmonic adder 8.
An odd-order harmonic component signal output by multiplication of the bass component signal Asinωt and the full-wave rectified signal (Equation (1)) can be expressed as Equation (2).

From the equation (2), the generated odd harmonic component signal does not contain a DC component. It can also be seen that the phase of the bass component signal matches.
FIG. 4 shows the frequency characteristics of the full-wave rectified signal (solid line) and the odd-order harmonic component signal (dotted line). As can be seen from FIG. 4, the odd-order harmonic component signal generates odd-order harmonic components (100 Hz, 300 Hz, 500 Hz,...) Of the bass component signal (100 Hz).

  The 90-degree phase converter 5 generates a 90-degree phase shift signal obtained by shifting the phase of the bass component signal by 90 degrees and outputs the 90-degree phase shift signal to the even-order harmonic multiplier 6.

The 90-degree phase conversion method may be any method that generates a 90-degree phase shift signal obtained by shifting the phase of the bass component signal by 90 degrees. For example, a processing method such as Hilbert conversion, differentiation, or integration is used.
Here, the 90 ° phase shift signal obtained by shifting the phase of the bass component signal Asinωt by 90 ° in the 90 ° phase converter 5 is Acosωt.

The even-order harmonic multiplier 6 multiplies the odd-order harmonic component signal output from the odd-order harmonic multiplier 11 and the 90-degree phase shift signal of the bass component signal output from the 90-degree phase converter 5, The even harmonic component signal generated as a result is output to the first amplitude adjustment unit 7.
Even-order harmonics generated by multiplying the odd-order harmonic component signal (formula (2)) output from the odd-order harmonic multiplier 11 and the 90-degree phase shift signal Acosωt output from the 90-degree phase converter 5 The component signal can be expressed as Equation (3).

  From equation (3), the even harmonic component signal generated does not contain a DC component. It can also be seen that the phase of the bass component signal matches.

  FIG. 5 shows frequency characteristics of the odd-order harmonic component signal (dotted line) and the even-order harmonic component signal (solid line). FIG. 5 shows that the even-order harmonic component signal generates even-order harmonic components (200 Hz, 400 Hz, 600 Hz,...) Of the bass component signal (100 Hz) and does not generate a DC component.

The first amplitude adjustment unit 7 adjusts the amplitude of the even-order harmonic component signal generated by the even-order harmonic multiplier 6 and outputs the even-order harmonic component signal whose amplitude has been adjusted to the harmonic adder 8. .
The first amplitude adjustment unit 7 aligns the power of the even-order harmonic component signal generated from the even-order harmonic multiplier 6 with the power of the odd-order harmonic component signal generated from the odd-order harmonic multiplier 11. Therefore, the amplitude adjustment is performed by multiplying the inverse of the amplitude value A of the bass component signal Asinωt.

  FIG. 6 shows the frequency characteristics of the odd-order harmonic component signal (dotted line) and the amplitude-adjusted even-order harmonic component signal (solid line). From FIG. 6, it can be seen that the power of the harmonic component signal of the adjacent order is a signal that is attenuated as the order is larger than before the amplitude adjustment (FIG. 5).

The harmonic adder 8 adds the odd-order harmonic component signal generated from the odd-order harmonic multiplier 11 and the even-order harmonic component signal adjusted in amplitude output from the first amplitude adjustment unit 7. The resulting harmonic component signal is output to the second amplitude adjustment unit 9.
The second amplitude adjustment unit 9 adjusts the amplitude of the harmonic component signal output from the harmonic adder 8 and outputs the harmonic component signal whose amplitude has been adjusted to the output generation adder 3.
The second amplitude adjustment unit 9 performs amplitude adjustment by multiplying the reciprocal of the amplitude value A in order to align the power of the harmonic component signal output from the harmonic adder 8 with the power of the bass component signal Asinωt.

FIG. 7 shows the frequency characteristics of the bass component signal (dotted line) and the harmonic component signal (solid line) whose amplitude has been adjusted. From FIG. 7, it can be seen that the harmonic component signal whose amplitude has been adjusted is composed of a harmonic component equivalent to the power of the bass component signal.
The second amplitude adjustment unit 9 multiplies the gain α in addition to the reciprocal of the amplitude value A, and changes the ratio of the harmonic component signal added to the input signal in the output generation adder 3.

  As described above, the odd-order harmonic multiplier 11 generates the odd-order harmonic component signal by multiplying the full-wave rectified signal output from the full-wave rectifier 10 and the bass component signal, and the even-order harmonic. The multiplier 6 multiplies the odd-order harmonic component signal generated by the odd-order harmonic multiplier 11 and the 90-degree phase shift signal obtained by shifting the phase of the bass component signal generated by the 90-degree phase converter 5 by 90 degrees. Therefore, even-order harmonic component signals having no DC component and no phase shift are generated, so that high-quality harmonic components without deterioration in sound quality can be generated. Further, since the second amplitude adjustment unit 9 multiplies the gain α in addition to the reciprocal of the amplitude value A, the ratio of the harmonic component signal to be added to the input signal changes, which is felt when the output signal is reproduced by a speaker. The bass effect can be changed.

Embodiment 2. FIG.
FIG. 8 is a block diagram showing a harmonic generation unit 2 of an audio signal reproduction device according to Embodiment 2 of the present invention. In the figure, parts different from FIG. 1 will be described. Regarding the harmonic generation unit 2, the same reference numerals as those in FIG.
The audio signal reproduction apparatus according to the second embodiment has a configuration in which an amplitude value calculation unit 12 that calculates the amplitude value A of the bass component signal Asinωt is added to the configuration of the first embodiment.

Next, the operation will be described.
The amplitude value calculation unit 12 inputs the bass component signal Asinωt and the 90-degree phase shift signal Acosωt output from the 90-degree phase conversion unit 5 to calculate the amplitude value A, and the calculation result is the first amplitude adjustment unit 7 and Output to the second amplitude adjustment unit 9.
The calculation of the amplitude value A is performed from equation (4) by using the trigonometric function formula.

  From the above, the even-order harmonic component signal generated by the even-order harmonic multiplier 6 and the harmonic component signal generated by the harmonic adder 8 are respectively converted into the first amplitude adjusting unit 7 and the second amplitude adjusting unit. In 9, the amplitude is adjusted by the amplitude value A calculated by the amplitude value calculation unit 12, whereby a high-quality harmonic component signal can be generated.

Embodiment 3 FIG.
FIG. 9 is a block diagram showing a harmonic generation unit 2 of an audio signal reproduction device according to Embodiment 3 of the present invention. In the figure, parts different from FIG. 1 will be described. With respect to the harmonic generation unit, the same reference numerals as those in FIG. The audio signal reproduction apparatus according to the third embodiment has a configuration in which an amplitude value calculation unit 12 that calculates the amplitude value A of the bass component signal Asinωt is added to the configuration of the first embodiment, and is different from the second embodiment. The point is that the input signal of the amplitude value calculation unit 12 is not the bass component signal Asinωt and the 90-degree phase shift signal Acosωt, but the full-wave rectification signal of the full-wave rectification unit 10 constituting the odd-order harmonic generation unit 4 is input. It is.

Next, the operation will be described.
The amplitude value calculator 12 receives the full-wave rectified signal output from the full-wave rectifier 10 and calculates the amplitude value A. The calculation result is sent to the first amplitude adjuster 7 and the second amplitude adjuster 9. Output.
The amplitude value is calculated by passing the full-wave rectified signal through a low-pass filter and using the resulting signal as the amplitude value of the bass component signal.

  From the above, the even-order harmonic component signal generated by the even-order harmonic multiplier 6 and the harmonic component signal generated by the harmonic adder 8 are respectively converted into the first amplitude adjusting unit 7 and the second amplitude adjusting unit. In 9, the amplitude is adjusted by the amplitude value A calculated by the amplitude value calculation unit 12, whereby a high-quality harmonic component signal can be generated.

Embodiment 4 FIG.
FIG. 10 is a block diagram showing a harmonic generation unit 2 of an audio signal reproduction device according to Embodiment 4 of the present invention. In the figure, parts different from those in FIGS. 1 and 8 will be described. Regarding the harmonic generation unit 2, the same reference numerals as those in FIG. 1 and FIG.
The audio signal reproducing apparatus according to the fourth embodiment has a configuration in which an amplitude value calculation unit 12 for calculating the amplitude value A of the bass component signal Asinωt is added to the configuration of the first embodiment, which is the same as that of the second embodiment shown in FIG. The difference is that the input signal of the amplitude value calculation unit 12 is not the bass component signal Asinωt and the 90 ° phase shift signal Acosωt but only the bass component signal Asinωt.

Next, the operation will be described.
The amplitude value calculation unit 12 receives the bass component signal Asinωt, calculates the amplitude value A, and outputs the calculation result to the first amplitude adjustment unit 7 and the second amplitude adjustment unit 9.
As the amplitude value A of the bass component signal, an RMS (Root Mean Square) calculation result of the bass component signal Asinωt is used.

  From the above, the even-order harmonic component signal generated by the even-order harmonic multiplier 6 and the harmonic component signal generated by the harmonic adder 8 are respectively converted into the first amplitude adjusting unit 7 and the second amplitude adjusting unit. In 9, the amplitude is adjusted by the amplitude value A calculated by the amplitude value calculation unit 12, whereby a high-quality harmonic component signal can be generated.

  The audio signal reproducing apparatus according to the present invention is useful for all thin products such as a liquid crystal TV (Television) and products in which the mounted speaker is miniaturized and it is difficult to obtain a sufficient low-frequency sound.

  1; Bass component extraction unit, 2; Harmonic generation unit, 3; Output generation adder, 4; Odd order harmonic generation unit, 5; 90 degree phase conversion unit, 6; Even order harmonic multiplier, 7; 1 amplitude adjustment unit, 8; harmonic adder, 9; second amplitude adjustment unit, 10; full-wave rectification unit, 11; odd harmonic multiplier, 12; amplitude value calculation unit.

Claims (8)

A bass component extraction unit that extracts a bass component signal from an audio signal that is an input signal;
An odd harmonic generation unit that generates an odd harmonic component signal from the bass component signal from the bass component extraction unit;
Similarly, a 90 degree phase conversion unit that generates a 90 degree phase shift signal from the bass component signal from the bass component extraction unit,
Even-order harmonic multiplier and even-order harmonics that generate an even-order harmonic component signal by multiplying the 90-degree phase shift signal of the 90-degree phase conversion unit and the odd-order harmonic component signal of the odd-order harmonic generation unit A first amplitude adjuster for adjusting the amplitude of the even harmonic component signal of the multiplier;
A harmonic adder that adds the odd-order harmonic component signal from the odd-order harmonic generation unit and the even-order harmonic component signal amplitude-adjusted by the first amplitude adjustment unit and outputs a harmonic component signal;
A second amplitude adjuster for adjusting the amplitude of the harmonic component signal of the harmonic adder;
An audio signal reproducing apparatus comprising: an output generation adder that outputs an output signal by adding an audio signal that is an input signal and a harmonic component signal that has been amplitude-adjusted by a second amplitude adjustment unit. The odd-order harmonic generation unit generates a full-wave rectification signal from the bass component signal,
The audio signal reproducing apparatus according to claim 1, further comprising an odd-order harmonic multiplier that multiplies the bass component signal and the full-wave rectified signal to generate an odd-order harmonic component signal.   3. The 90-degree phase conversion unit generates a 90-degree phase shift signal of the bass component signal by shifting the phase of the bass component signal by 90 degrees by performing a Hilbert transform on the bass component signal. Audio signal playback device.   3. The audio according to claim 1, wherein the 90-degree phase conversion unit differentiates the bass component signal to shift the phase of the bass component signal by 90 degrees to generate a 90-degree phase shift signal of the bass component signal. Signal reproduction device.   3. The audio according to claim 1, wherein the 90-degree phase conversion unit integrates the bass component signal to shift the phase of the bass component signal by 90 degrees to generate a 90-degree phase shift signal of the bass component signal. Signal reproduction device.   An amplitude value calculation unit that calculates an amplitude value of the bass component signal from the square root of the square sum of the 90-degree phase-shifted signal obtained by shifting the phase of the bass component signal and the bass component signal by 90 degrees; and first and second amplitude adjustment units 6. The audio signal reproducing apparatus according to claim 1, wherein amplitude adjustment of the even-order harmonic component signal and the harmonic component signal is performed according to the amplitude value from the amplitude width calculation unit.   A full-wave rectification signal output from the full-wave rectification unit is passed through a low-pass filter, and an amplitude value calculation unit that uses the signal output as a result as an amplitude value of the bass component signal is provided. The first and second amplitude adjustment units include 6. The audio signal reproduction device according to claim 1, wherein amplitude adjustment of the even-order harmonic component signal and the harmonic component signal is performed based on the amplitude value from the amplitude width calculation unit.   An RMS (Root Mean Square) is calculated from the bass component signal, and an amplitude value calculation unit that uses the calculation result as an amplitude value of the bass component signal is provided. The first and second amplitude adjustment units are amplitudes from the amplitude width calculation unit. 6. The audio signal reproducing apparatus according to claim 1, wherein the amplitude adjustment of the even-order harmonic component signal and the harmonic component signal is performed according to the value.

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