JPH0632542B2 - Sound reproduction device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a sound reproducing device capable of reproducing a low frequency range of sound.

BACKGROUND ART It is sometimes difficult for a general sound reproducing apparatus to reproduce an extremely low frequency band (20 to 50 Hz) depending on the type of program source. For example, in the case of a record, since the amplitude in the ultra-low frequency range becomes extremely large, skipping during playback and the possibility of overcutting by the cutting device are included. In magnetic tapes and frequency-modulated broadcasts, the presence of ultra-low frequencies may adversely affect the overall reproduced sound as distortion, and similarly attenuates signals below 60 Hz. Even if you use, you cannot play the very low frequencies.

A typical prior art solution to this problem is shown in FIG. The signal from the acoustic signal source 1 is given to the amplifier circuit 4 from the line 2 through the addition circuit 3, and the speaker 5 is driven. The acoustic signal from the acoustic signal source 1 is also taken out by the bandpass filter 6 after only the component of 60 to 120 Hz is waved. The output of the bandpass filter 6 has the waveform shown in FIG. 5 (1), for example. The waveform shaping circuit 7 converts the output from the bandpass filter 6 into a square wave corresponding to the input signal frequency, and derives the signal shown in FIG. 5 (2). The frequency dividing circuit 8 frequency-divides the output from the waveform shaping circuit 7 and supplies the low-pass filter 9 with a signal having the waveform shown in FIG. The output from the low-pass filter 9 is as shown in FIG. 5 (4), is added to the adder circuit 3, is converted into a sine wave corresponding to 1/2 frequency, and is added to the original signal.

Problems to be Solved by the Invention In such a prior art, since the frequency divider circuit 8 generates a 1/2 frequency, the waveform shaping circuit 7 generates a square wave. Therefore, the low-pass filter 9 is required to be a high-order filter, and if the characteristics of the low-pass filter 9 are not good, the low-pass filter 9 contains not only a 1/2 frequency but also a higher harmonic component of 2 times or more. The signal will be given to the adder circuit 3. This leads to deterioration of sound quality and localization.

An object of the present invention is to provide a sound reproducing device capable of enhancing the low frequency range without deteriorating the sound quality and the sense of localization.

Means for Solving the Problems The present invention relates to an acoustic signal source, a filter for wavering a low-frequency signal from the acoustic signal source, and a frequency-voltage converter for frequency-voltage converting the low-frequency signal waved by the filter. A voltage-controlled oscillator whose oscillation frequency is controlled by the voltage output from the frequency-voltage converter, an envelope detection circuit for envelope-detecting the low-frequency signal waved by the filter, and a detection output of the envelope detection circuit. A sound reproduction device comprising: a multiplication circuit that multiplies the oscillation output of the voltage controlled oscillator; and an adder that adds the output signal of the multiplication circuit and the signal of the acoustic signal source.

Effect According to the present invention, in order to be able to reproduce the low frequency range of the sound, a filter that waves the low frequency signal, a frequency voltage converter to which the output is applied, a voltage controlled oscillator, and a filter are used. It is provided with a detection circuit for envelope-detecting the low-frequency signal, a multiplication circuit, and an adder, and particularly, reproduction of extremely low-frequency sound is enabled by an analog circuit.

Embodiment FIG. 1 is a block diagram of an embodiment of the present invention. An acoustic signal from an audio signal source 11 such as a reproducing device such as a record and a magnetic tape or a receiver such as a radio broadcast is
It is given to the adder circuit 13 from the line 12 and is supplied to the amplifier circuit 14
Is amplified by the speaker 15 and is sonicated by the speaker 15. The acoustic signal from the acoustic signal source 11 is also provided to the bandpass filter 16. This band pass filter 1
6 is 60 to 120 Hz of the acoustic signal from the acoustic signal source 11.
Wave out and take out. The acoustic signal from the bandpass filter 16 is given to the frequency / voltage conversion circuit 17 to derive a DC voltage corresponding to the frequency.

FIG. 2 shows the characteristics of the frequency / voltage conversion circuit 17. As the frequency of the input signal increases, the DC voltage generated increases, thus obtaining a voltage corresponding to the frequency.

The voltage-controlled oscillation circuit 18 responds to the DC voltage from the frequency / voltage conversion circuit 17, and derives a signal having a sinusoidal oscillation frequency corresponding to the voltage, as shown in FIG. Frequency / voltage conversion circuit 17 and voltage controlled oscillation circuit 1
8 cooperate with each other to oscillate at a frequency half the output frequency of the bandpass filter 16. This voltage controlled oscillator circuit 1
The output from 8 is given to the multiplication circuit 19.

The signal from the bandpass filter 16 is also supplied to the envelope detection circuit 20. The envelope detection circuit 20 generates a signal having an envelope waveform of a low frequency acoustic signal of 60 to 120 Hz. The output level from the envelope detection circuit 20 corresponds to the level of the acoustic signal from the acoustic signal source 11. The multiplication circuit 19 multiplies the signal generated from the voltage controlled oscillation circuit 18 by the output from the envelope detection circuit 20, and the level of the signal from the voltage controlled oscillation circuit 18 corresponds to the level of the envelope detection circuit 20. The level is adjusted and given to the adder circuit 13. The adder circuit 13 uses the acoustic signal source 1 via the line 12.
1 from the acoustic signal and the super low frequency range 30 from the multiplication circuit 19
The sound signal of 60 Hz is added. In this way, when the frequency of the acoustic signal from the acoustic signal source 11 is 80 Hz, for example, the frequency / voltage conversion circuit 17 operates, for example, in the second
As is apparent from the figure, a direct current voltage of 1 V is generated, which causes the voltage controlled oscillator circuit 18 to generate a sine wave having a frequency half that of the acoustic signal from the acoustic signal source 11, that is, 40 Hz. . The multiplication circuit 19 is a bandpass filter 1
In order to obtain the level of the acoustic signal from 6, the output from the envelope detection circuit 20 is multiplied. In this way, it is possible to reproduce rich super bass from the speaker 15 driven by the amplifier circuit 14. The envelope detection circuit 20 may be omitted.

Advantageous Effects of Invention According to the present invention, it is possible to easily reproduce a low frequency range of sound even in an analog circuit without using a complicated digital circuit, and a filter and frequency-voltage conversion that can be realized in a small circuit scale even in an analog circuit. And a voltage-controlled oscillator, an envelope detection circuit, a multiplication circuit, and an adder. With such a simple configuration, it is possible to enhance the low frequency range without deteriorating the sound quality and localization. become.

[Brief description of drawings]

1 is a block diagram of an embodiment of the present invention, FIG. 2 is a graph showing the characteristics of the frequency / voltage conversion circuit 17, FIG. 3 is a graph for explaining the operation of the voltage controlled oscillator circuit 18, and FIG. The figure is a block diagram of the prior art, and FIG. 5 is a waveform diagram for explaining the operation of the prior art shown in FIG. 11 ... Acoustic signal source, 13 ... Addition circuit, 14 ... Amplification circuit, 15 ... Speaker, 16 ... Bandpass filter, 17 ... Frequency / voltage conversion circuit, 18 ... Voltage controlled oscillation circuit, 19 ... … Multiplier circuit, 20 …… Envelope detector circuit

Claims (1)

[Claims] 1. An acoustic signal source, a filter that waves a low-frequency signal from the acoustic signal source, a frequency-voltage converter that frequency-voltage converts the low-frequency signal that is waved by the filter, and the frequency-voltage converter. A voltage-controlled oscillator whose oscillation frequency is controlled by a voltage output from the filter, an envelope detection circuit for envelope-detecting a low-frequency signal waved by the filter, a detection output of the envelope detection circuit, and an oscillation of the voltage-controlled oscillator. An audio reproducing apparatus comprising: a multiplication circuit for multiplying outputs, and an adder for adding the output signal of the multiplication circuit and the signal of the audio signal source.