JPH06141391A - Acoustic reproduction equipment - Google Patents

Abstract

PURPOSE:To provide an acoustic reproduction equipment at a low cost in which a signal representing a frequency component not included in an inputted acoustic signal is generated and the acoustic signal representing a sound close to a natural sound or a music sound of a natural music instrument or the like is obtained. CONSTITUTION:A mixing signal including frequency components of the sum and the difference between a frequency of an acoustic signal and a frequency of a sine wave signal is generated by mixing the sinusoidal wave signal having the prescribed frequency with the inputted acoustic signal in mixing circuits 14a-14c. Harmonic signals comprising the sum frequency component are extracted by high pass filters 16a-16c among mixing signals outputted respectively from the mixing circuits 14a-14c and each higher harmonic signal outputted from the high pass filters 16a-16c is added to the acoustic signal by an adder means 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound reproducing apparatus for converting an input acoustic signal into an acoustic signal containing a high frequency component not included in the acoustic signal. For example, the input acoustic signal is digital. The present invention relates to a sound reproducing device suitable for a signal.

[0002]

2. Description of the Related Art CDs (Compact Discs), etc.
Natural sounds and musical sounds of natural musical instruments are recorded as digital signals. The digital signal recorded on the CD or the like is converted into an analog signal representing sound by a sound reproducing device and reproduced as sound through a speaker or the like.

By the way, the sound is converted into a digital signal by the C signal.
When recording on D or the like, sampling is performed at a frequency that is at least twice the highest frequency of the waveform of the sound to be reproduced. The human audible band is set to about 20 Hz to 20 kHz,
For this reason, there are currently about 20k for sound recording media such as CDs
A digital signal sampled at about 40 kHz is recorded so as to be reproduced up to about Hz.

However, natural sounds and sounds of natural musical instruments have two
It contains a high frequency component of 0 kHz or more and about 50 to 70 kHz, and although it is said that the human ear cannot hear the sound of 20 kHz or more, it is 20 kHz.
There are many people who can distinguish the difference in the'timbre 'between the sound with a frequency of less than Hz and the sound with a frequency of more than 20 kHz. On the other hand, as described above, since the digital signal recorded on the CD or the like is sampled at about 40 kHz, it is obtained by converting this digital signal into an analog signal by a conventional sound reproducing device and reproducing it through a speaker or the like. The sound does not include frequency components exceeding 20 kHz. For this reason, there is a problem that particularly when the sound changes abruptly, for example, at a moment when a certain sound is emitted, it may be heard as a'timbre 'different from a natural sound.

Some conventional sound reproducing apparatuses employ a DA conversion system called "legato link conversion system" in order to solve this problem. The "legato link conversion method" is a system for restoring a signal of 20 kHz or more not included in a CD or the like by a digital operation using a DSP (digital signal processor). The method of using this DSP calculates the interpolation function according to the principle that "the output level of a natural musical instrument tends to decrease in inverse proportion to the frequency of any music".
This interpolation function is used to interpolate between sampling points when a digital signal is recorded on a CD or the like to reproduce sound of 20 kHz or higher (ASCII, vol. 1).
6, # 7 July 1992).

[0006]

The method using the DSP has the problems that it is not easy to determine the interpolation function, and the structure of the sound reproducing device is complicated, which increases the cost. In view of the above circumstances, it is an object of the present invention to provide a low-cost sound reproducing device that converts an input acoustic signal into an acoustic signal representing a high frequency component that is not included in this acoustic signal.

[0007]

SUMMARY OF THE INVENTION A first sound reproducing apparatus of the present invention for achieving the above object receives an audio signal and mixes a sine wave signal of a predetermined frequency with the audio signal to generate an audio signal. The mixing means for generating a mixing signal containing the frequency component of the sum and difference between the frequency of the signal and the frequency of the sine wave signal, and the harmonic signal composed of the sum frequency component of the mixing signals output from the mixing means The present invention is characterized by including a high-pass filter for extracting and an adding unit for adding a harmonic signal output from the high-pass filter to an acoustic signal.

Here, it is preferable that the sound reproducing apparatus is provided with weighting means for weighting the harmonic signal.
In addition, it is preferable that the sound reproduction device includes a phase adjusting unit that adjusts the phase of the harmonic signal. Further, the second sound reproducing device of the present invention for achieving the above-mentioned object inputs the sound signal and mixes the sine wave signals of different frequencies to the sound signal to obtain the frequency of the sound signal and each sine wave. A plurality of mixing means for generating respective mixing signals containing frequency components of sum and difference with the frequency of the signal, and respective harmonics composed of sum frequency components of the respective mixing signals outputted from the plurality of mixing means It is characterized by comprising a plurality of high-pass filters for extracting signals, and an adding means for adding each harmonic signal output from each of the plurality of high-pass filters to an acoustic signal.

[0009]

The principle of mixing an audio signal by the mixing circuit of the audio reproducing apparatus of the present invention will be described. Generally, an acoustic signal f (t) having a period T is calculated by Fourier series if there is no DC component.

[0010]

[Equation 1]

Is represented as here

[0012]

[Equation 2]

[0013] Here, cos (nωt) · cos (ω ₀ t) = ½ {cos (nω−ω ₀ ) t + cos (nω + ω ₀ ) t} sin (nωt) · cos (ω ₀ t) = 1/2 {sin Since (nω + ω ₀ ) t + sin (nω−ω ₀ ) t},

[0014]

[Equation 3]

[0015] As shown in the above principle, first, in the mixing circuit, a sine wave signal having a predetermined frequency (ω _{0 in the} above) is mixed with the input acoustic signal f (t), so that the frequency of the input acoustic signal and the sine wave are compared. A mixing signal including the frequency components of the sum and the difference with the frequency of the wave signal is generated.

Next, in the high-pass filter, a harmonic signal composed of the sum frequency component is extracted from the mixing signal output from the mixing circuit, and then the harmonic signal output from the high-pass filter is added by the adding means. Is added to the acoustic signal. As a result, an acoustic signal including a frequency component that is not included in the input acoustic signal is generated.

If a weighting circuit is provided, the high
Since the harmonic signals are weighted, natural sounds and instruments
Generating an acoustic signal that represents a sound that is closer to the musical sound of
You can The acoustic signal f (t) is classified up to the first derivative.
Of the Fourier series
According to the formula, a in the above formula (1)_n , B_n But | a _n 
| <1 / n, | b_n | <1 / n. For this reason,
For example, weight the harmonic signal by -20 log₂ n, that is,
−6dB down / decided to have octave characteristics
, The weighting value is 1/2
If there is no need for weighting.

Further, when the phase adjusting circuit is provided, the phases of the input acoustic signal and harmonic signal are adjusted,
Also in this case, it is possible to generate an acoustic signal that represents a sound that is closer to a natural sound or a musical sound of a natural musical instrument. Furthermore, when a plurality of mixing circuits and a plurality of high-pass filters are provided and a plurality of harmonic signals are added to the input acoustic signal by the adding means, an acoustic signal containing various high frequency components is generated. Since the sound signal is generated, a sound signal that represents a sound that is even closer to a natural sound or a musical sound of a natural musical instrument is generated.

[0019]

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a schematic configuration of a sound reproducing device according to a first embodiment of the present invention. Sound reproduction device 10 of the present embodiment
A digital audio signal is input from an external device such as a CD. This digital acoustic signal is expressed by the following equation, and the angular frequency ω ₀ (frequency 20 kHz; ω ₀ = 2π × 2
It does not contain components above 0 kHz).

[0020]

[Equation 4]

[0021]

[Equation 5]

This acoustic signal is first converted into an analog acoustic signal by the D / A converter 12, and this analog acoustic signal is converted into 3
It is input to each of the two mixing circuits 14a, 14b, 14c. These three mixing circuits 14a, 14
In each of b and 14c, the analog acoustic signal is mixed with a sine wave signal of frequencies ω ₀ , 2ω ₀ , and 3ω ₀ , respectively. For example, in the case of the mixing circuit 14a, as described above, the frequency components of the sum and difference between the frequency of the analog acoustic signal and the frequency ω ₀ of the sine wave signal are represented by the following equation (2). The included mixing signal is generated.

[0023]

[Equation 6]

The mixing signal generated by the mixing circuit 14a is schematically shown in FIG. As shown in FIG. 2, the mixing signal 14 includes a sum frequency component 14d and a difference frequency component 14e, and these two frequency components are symmetrical with respect to the frequency ω ₀ . Similarly, in the mixing circuits 14b and 14c, the frequency 2
A mixing signal including frequency components symmetrical with respect to ω ₀ and 3ω ₀ is generated. In this way, the mixing circuit 14
At a, 14b, and 14c, a mixing signal including frequency components that were not included in the digital audio signal input to the audio reproduction device 10 is generated.

The respective mixing signals output from the respective mixing circuits 14a, 14b, 14c are input to the high-pass filters 16a, 16b, 16c, and the harmonic signals having the sum frequency component of the respective mixing signals are high-pass filters 16a, 16b. , 16c, respectively. The extracted harmonic signals are input to weighting circuits 18a, 18b, 18c, respectively, and k ₁ , k ₂ , k ₃ are input.
Weighting represented by is performed.

The harmonic signals output from the weighting circuits 18a, 18b and 18c are input to the phase adjusting circuits 20a, 20b and 20c, respectively, and the phases of the harmonic signals are changed by the phase adjusting circuits 20a, 20b and 20c. Adjusted. The above harmonic signals whose phases have been adjusted are input to the adder circuit 22 where they are added to the acoustic signals in the state of being output from the D / A converter 12. The result of this addition is schematically shown in FIG. D /
Acoustic signal 22a in the state as output from the A converter 12
As a result of the addition of the harmonic signal 22b and the harmonic signal 22b, an acoustic signal including a frequency component that is not included in the acoustic signal input to the acoustic reproduction device 10 is generated as illustrated in FIG. As a result, it is possible to obtain an acoustic signal that represents a sound close to a natural sound or a musical sound of a natural musical instrument. This acoustic signal is reproduced as a sound through a speaker (not shown) or the like to obtain a sound close to a natural sound or a musical sound of a natural musical instrument.

In the above embodiment, three mixing circuits 1 are used.
4a, 14b, and 14c each have a frequency ω
₀ 2ω₀ 3ω₀ Mixing sine wave signals
However, the frequency ω₀ The sine wave signal of
Even the generation of harmonics provides a significant acoustic improvement. one
However, using more mixing circuits, frequency 4ω
₀ 5ω₀ , ... Mixing sine wave signal into acoustic signal
It may be configured to. With this configuration, the higher
Since an acoustic signal containing wavenumber components is generated,
It is possible to obtain an acoustic signal that represents a sound closer to that of a natural musical instrument.
It

A second embodiment of the sound reproducing device of the present invention will be described with reference to FIG. The sound reproducing apparatus 10 (see FIG. 1) of the first embodiment converts the input digital acoustic signal into an analog acoustic signal by the D / A converter 12 (see FIG. 1) and outputs a signal in the state of this analog acoustic signal. On the other hand, the sound reproducing apparatus 30 of the second embodiment processes the input digital sound signal in the analog state without converting it into the analog sound signal, and the D / A converter 32 performs the analog processing. This is a configuration for converting into an acoustic signal and outputting.

As shown in FIG. 4, the sound reproducing apparatus 30 has a frequency ω ₀ for the input sound signal as in the first embodiment.
Mixing circuits 34a, 34b, 34c for respectively mixing 2ω ₀ , 3ω ₀ sine wave signals, a high-pass filter 36a for extracting each harmonic signal from each mixing signal output from each of these mixing circuits 34a, 34b, 34c, 36b, 36c, these high-pass filters 36a, 36b, 36c weighting circuit 38a for weighting represented by k _1, k _2, k ₃ to each harmonic signals output from, 38b, 38c, these weighting circuit An adder circuit 40 for adding the respective harmonic signals output from each of 38a, 38b, and 38c is provided.
Processing similar to that of the sound reproducing apparatus 10 (see FIG. 1) of the embodiment is performed, but the above high-pass filters 36a, 36b,
Reference numeral 36c is a configuration in which the phases of the input audio signals are not shifted, and therefore the audio reproduction device 30 is not provided with a phase adjustment circuit. The acoustic signal output from the adding circuit 40 is converted into an analog acoustic signal by the D / A converter 32 and output as described above.

The sound reproducing device 30 of this embodiment can also obtain the same effects as the sound reproducing device 10 of the first embodiment.

[0031]

As described above, in the sound reproducing apparatus of the present invention, a sine wave signal having a predetermined frequency is mixed with the input sound signal to include a frequency component not included in the input sound signal. Since the audible sound signal is generated, an audible signal representing a sound close to a natural sound or a musical sound of a natural musical instrument can be obtained. By reproducing this acoustic signal as a sound through a speaker or the like, a sound close to a natural sound or a musical sound of a natural musical instrument can be obtained even when the sound changes rapidly.

The sound signal processing method performed by the sound reproducing apparatus of the present invention enables real-time signal processing,
In addition, it becomes a low-cost sound reproducing device.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a sound reproducing device according to a first embodiment.

FIG. 2 is a graph schematically showing a mixing signal generated by a mixing circuit.

[FIG. 3] Each harmonic signal and D output from the phase adjustment circuit
It is a graph which shows typically the result of having added the acoustic signal of the state as it was output from the / A converter.

FIG. 4 is a block diagram showing a schematic configuration of a sound reproducing device according to a second embodiment.

[Explanation of symbols]

10, 30 Sound reproduction device 12, 32 D / A converter 14a, 14b, 14c, 34a, 34b, 34c Mixing circuit 16a, 16b, 16c, 36a, 36b, 36c High-pass filter 18a, 18b, 18c, 38a, 38b, 38c Weighting circuit 20a, 20b, 20c Phase adjustment circuit 22, 40 Adder circuit

Claims (4)

[Claims] 1. An acoustic signal is input and a sine wave signal having a predetermined frequency is mixed with the acoustic signal to include a frequency component of a sum and a difference between the frequency of the acoustic signal and the frequency of the sine wave signal. Mixing means for generating a mixing signal, a high-pass filter for extracting a harmonic signal composed of a sum frequency component of the mixing signal output from the mixing means, and a harmonic signal output from the high-pass filter for the acoustic signal. An audio reproducing apparatus comprising: an adding unit that adds to a signal. 2. The sound reproducing apparatus according to claim 1, further comprising weighting means for weighting the harmonic signals. 3. The sound reproducing device according to claim 1, further comprising phase adjusting means for adjusting the phase of the harmonic signal. 4. A frequency component of a sum and a difference between the frequency of the acoustic signal and the frequencies of the respective sine wave signals by inputting the acoustic signal and mixing the sine wave signals of different predetermined frequencies with the acoustic signal. A plurality of mixing means for generating each mixing signal containing, and a plurality of high-pass filters for extracting each harmonic signal composed of the sum frequency component of each mixing signal output from each of the plurality of mixing means, An audio reproducing apparatus, comprising: an adding unit that adds each harmonic signal output from each of the plurality of high-pass filters to the audio signal.