JPH11136791A - Reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a reproduced sound in response to the linearity of a transducer in the case of reproducing an audible signal at an audible band so as to produce a sound pressure change through the use of the transducer. SOLUTION: An audio signal at an audible band is given from an input terminal 1 to a preamplifier 2. A speaker 4 producing a sound pressure change in response to a drive signal with a frequency band wider than the audio band is connected to an output of a power amplifier 3. An oscillator 5 produces an AC sine wave signal whose peak level is constant. A mixing circuit 6 mixes an AC signal and an audio signal and gives the mixed signal to the power amplifier 3. The speaker 4 is driven by the mixed signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reproducing apparatus, and more particularly, to a reproducing apparatus which reproduces an audio signal in an audible band using a transducer to cause a change in sound pressure.

[0002]

2. Description of the Related Art Conventionally, in order to provide an audio signal to a listener, a driving current corresponding to the audio signal is supplied to a transducer (electric-to-sound pressure conversion element) such as a speaker, a headphone, an earphone, or the like. The sound pressure changes according to the time.

FIG. 3 is a block diagram showing an example of a conventional reproducing apparatus.

In the figure, reference numeral 102 denotes a preamplifier,
The audio signal in the audible band from the input terminal 101 is subjected to predetermined processing and output. A power amplifier (power amplifier) 103 amplifies the power of the preamplifier output and outputs a drive current. This drive current is supplied to the speaker 104. The speaker 104 has a well-known configuration having a diaphragm or the like that is driven and driven by a drive current, and reproduces a sound by the vibration.

[0005]

However, in the conventional reproducing apparatus, the operating current of the transducer changes according to the magnitude of the audio signal, but the nonlinearity of the small signal sometimes becomes a problem.

FIG. 4 is a waveform diagram for explaining this problem, and shows signal waveforms at various parts in FIG. 4A illustrates an input audio signal at the input terminal 101, and FIG. 4B illustrates an output signal of the preamplifier 102.

FIGS. 1C and 1D show two examples of driving current waveforms to the speaker 104, wherein FIG. 1C shows a low-level reproduction and FIG. 2D shows a high-level reproduction.

Here, the speaker 104 operates linearly outside the small signal region indicated by the broken line, but operates nonlinearly within the small signal region. This is because the operating current of the speaker 104 changes depending on the magnitude of the input audio signal, but it is difficult to vibrate the diaphragm itself or change the air pressure on the surface of the diaphragm during a small signal. Does not change according to the sound pressure. Therefore, in the small signal area, distortion occurs, and only audio with poor linearity can be reproduced. That is, FIG.
As can be seen from (D), most of the input signal enters the area where the linearity of the speaker 104 is poor when reproducing the low-level signal. In addition, even when a large-level signal is reproduced, the small-amplitude portion enters a region having poor linearity.

Therefore, the present invention has been made in view of the above-mentioned points, and has as its object to provide a reproducing apparatus which solves the above-mentioned problems.

[0010]

According to a first aspect of the present invention, there is provided an apparatus for inputting an audio signal in an audible band and a driving signal having a wider band than the audible band. And a driving unit for outputting the driving signal to the converting unit based on the audio signal, wherein the reproducing unit reproduces the audio signal. Comprises a signal generating means for generating an AC signal of a constant level, and a mixing means for mixing the AC signal and the audio signal and supplying the mixed signal to the driving means.

In this case, in the apparatus according to the present invention, when the peak value is supplied to the conversion means via the driving means, the mixed audio signal is It may be a value that falls within a linearly operable region outside the non-linear region of the electric-to-sound pressure conversion characteristic of the converter.

Here, in the apparatus according to the present invention, the signal generating means may be an oscillator for generating a sine wave signal as the AC signal.

Here, in the apparatus according to the present invention, the frequency of the AC signal from the oscillator may be higher than the maximum frequency of the audio signal.

Here, in the apparatus according to the fifth aspect of the present invention, the frequency of the AC signal from the oscillator can be lower than the minimum frequency of the audio signal.

Here, in the apparatus according to the present invention, the AC signal may be amplitude-modulated by the audio signal by the mixing means.

Here, in the apparatus according to the present invention, the driving means may be a power amplifier for supplying a driving current for a speaker as the conversion means.

Here, in the device of the present invention described in claim 8, the driving means may be a power amplifier for supplying a driving current for headphones as the conversion means.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a reproducing apparatus to which the present invention is applied.

In the figure, reference numeral 2 denotes a preamplifier, which is an audible band (20 Hz to 20000) input from an input terminal 1.
Hz) is subjected to predetermined processing and output. For example, equalization is used for audio tape recorders and video tape recorders, and balance control, treble,
This is a boost adjustment for each band of a bus or the like. Reference numeral 3 denotes a power amplifier (power amplifier) that power-amplifies an input audio signal and outputs a drive current. This drive current is supplied to the speaker 4.

The loudspeaker 4 has a well-known configuration having a diaphragm or the like which is driven and driven by a drive current, and reproduces sound by changing the air pressure near the diaphragm by this vibration. The speaker 4 is freely connectable to a reproducing apparatus, and by changing the specification of the power amplifier 3, another transducer (electric-sound pressure conversion element) such as an earphone headphone or an earphone is connected to supply a driving current. As is well-known, it is also possible to generate a sound pressure change corresponding to the audio signal to provide the reproduced audio signal to the listener.

However, in the present embodiment, the power amplifier 3 can amplify and output a signal in a band other than the audible band, for example, a band of DC to 30000 Hz, and the transducer also uses this band other than the audible band as an air pressure. Can be converted into a change. However, DC need not be converted.

5 is an oscillator (OSC), for example, 1
It generates and outputs an AC sine wave signal outside the audible band of 0 Hz or 30,000 Hz. This sine wave signal has a constant peak value. Reference numeral 6 denotes a mixing circuit, which superimposes the output signal of the oscillator 5 and the preamplifier output signal, and supplies the superimposed signal to the power amplifier 3.

FIG. 2 shows signal waveforms at various points in FIG.

In FIG. 1, (A) shows an input audio signal at the input terminal 1, and (B) shows an output signal of the preamplifier 2. Here, the output signal of the preamplifier 2 is obtained by subjecting an input audio signal to predetermined signal processing and attenuated. Further, although this waveform shows a state where the amplitude of the input audio signal is attenuated, the waveform may be such that the frequency characteristic is changed by controlling for each band as described above.

FIG. 3C shows the output signal of the oscillator 5, and its envelope is represented by a solid line, and the hatched portion represents a 30000 Hz sine wave exceeding the audible band. The envelope is a straight line, indicating that the peak value is at a constant level.

FIG. 3D shows the output current of the power amplifier 3, whose envelope is indicated by a solid line, and the hatched portion indicates that a sine wave of 30,000 Hz exceeding the audible band is superimposed. . This current waveform is the same as the output waveform of the mix circuit 6, but is a waveform obtained by AM-modulating a constant level sine wave with the audio signal output from the preamplifier.

The envelope level of the output current is determined by the peak value of the output signal of the oscillator 5, and the peak value of the sine wave signal is obtained by mixing the output signal mixed by the mixing circuit 6 through the power amplifier 3 to the speaker 4 or the like. When supplied to the transducer, the mixed audio signal is set to a value that falls within a linearly operable region outside the non-linear region of the electric-to-sound pressure conversion characteristic of the speaker 4.

That is, in FIG. 2D, the speaker 4 operates linearly outside the small signal region above and below the broken line.
The area of the small signal sandwiched between the broken lines is a range of the non-linear operation in which the speaker 4 does not cause a faithful change in sound pressure according to the input audio signal. As can be seen from FIG. 2 (D), FIG.
The speaker 104 operates by a drive current having an envelope having a waveform similar to that of the audio signal. The audio signal to be reproduced exists as an envelope waveform outside the small signal region where the speaker 104 operates linearly, and a sine wave outside the audible band of a certain level exists in the small signal region sandwiched between the broken lines where the speaker 104 operates nonlinearly. Just do it.

Accordingly, the sound pressure change caused by the operation of the speaker 104 is as shown in FIG. 2D, and the listener can hear only the input sound in the audible band (20 Hz to 20,000 Hz) corresponding to the envelope waveform. Becomes

According to the present embodiment, the speaker is operated in response to the audio signal in a region outside the non-linear operation region of the speaker. It is possible to provide high-quality reproduced sound with good linearity over an area from a small level to a large level of a signal.

The present invention can be applied not only to a speaker but also to an audio reproducing apparatus for driving and reproducing another transducer. In the above embodiment, the oscillator 5 oscillates and outputs a sine wave having a frequency higher than the audible band, but may output a sine wave having a frequency lower than the audible band.

[0033]

As described above, according to the present invention, a drive signal is output to a conversion means for generating a sound pressure change corresponding to a drive signal wider than the audible band, based on the audio signal in the audible band. A driving means, a signal generating means for generating an AC signal having a constant peak value, and a mixing means for supplying a signal obtained by mixing the AC signal and the audio signal to the driving means. To generate a sound pressure change and output the audible band as a reproduced sound, whereby a good characteristic corresponding to the characteristic of the conversion means can be obtained by the peak value.

The effect is obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a reproducing apparatus to which the present invention is applied.

FIG. 2 is a waveform chart showing signal waveforms at various parts in FIG.

FIG. 3 is a block diagram illustrating an example of a conventional reproducing apparatus.

FIG. 4 is a waveform chart for explaining a problem of the conventional reproducing apparatus.

[Explanation of symbols]

 1,101 input terminal 2,102 preamplifier 3,103 power amplifier 4,104 speaker 5 oscillator 6 mix circuit

Claims (8)

[Claims] An input means for inputting an audio signal in an audible band, and a conversion means for generating a sound pressure change according to a drive signal wider than the audible band are freely connectable, and the conversion is performed based on the audio signal. A reproducing device for reproducing the audio signal; a signal generating device for generating an AC signal having a constant peak value; and mixing the AC signal and the audio signal. And a mixing means for supplying the mixed signal to the driving means. 2. The peak value, when the mixed signal is supplied to the conversion unit via the driving unit,
2. The reproducing apparatus according to claim 1, wherein the mixed audio signal is set to a value that falls within a linearly operable region outside a non-linear region of the electric-to-sound pressure conversion characteristic of the conversion unit. 3. The reproducing apparatus according to claim 1, wherein the signal generating unit is an oscillator that generates a sine wave signal as the AC signal. 4. The reproducing apparatus according to claim 3, wherein a frequency of the AC signal from the oscillator is higher than a maximum frequency of the audio signal. 5. The reproducing apparatus according to claim 3, wherein a frequency of the AC signal from the oscillator is lower than a minimum frequency of the audio signal. 6. The reproducing apparatus according to claim 1, wherein the AC signal is amplitude-modulated with the audio signal by the mixing unit. 7. The reproducing apparatus according to claim 1, wherein the driving unit is a power amplifier that supplies a driving current for a speaker as the conversion unit. 8. The reproducing apparatus according to claim 1, wherein the driving unit is a power amplifier that supplies a driving current for headphones as the conversion unit.