JPS60244189A - acoustic transducer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to an acoustic conversion method in which a PCM (pulse code modulation) acoustic signal is directly inputted without going through a converter and converted into the original acoustic signal. It is related to vessels.

[Conventional technology]

One common method for restoring a PCM signal is to convert the PCM signal into an analog signal by electrically converting it into an analog signal, which is then amplified by an amplifier to drive an electroacoustic transducer. It is being

On the other hand, another method is to provide acoustic transducer units each consisting of an electric vibrating element and a signal electrode for driving the electric vibrating element in response to each bit signal of the PCM code, and convert these units with the corresponding bit signal of the PCM code. Direct drive, D/A via the mechanical system or acoustic system of the acoustic conversion unit
There is a way to do the conversion. This is a so-called digital speaker, which performs D/A conversion using a mechanical or acoustic system, so a D/A converter is unnecessary compared to electrical restoration methods. In this acoustic converter, it is necessary to weight each bit signal of the pcM code in order to perform D/A conversion.
Conventionally, this has been done by changing the settings of the acoustic conversion efficiency of each acoustic conversion unit. For example, Fig. 1 shows an acoustic transducer in which signal electrodes arranged concentrically with different areas are provided on an electric vibrating element, as proposed in Japanese Patent Application Laid-Open No. 58-121897. The acoustic conversion elements (22) N2 to Nr are configured by the elements.

In this case, the electrodes for the upper bits are arranged on the outer periphery and the electrodes for the lower bits on the inner periphery, but the conversion efficiency can be improved by adjusting the area ratio of each signal electrode 32, 33, ..., 3r. I have a military setting. That is, in the acoustic transducer of FIG. 1, assuming that the area ratio is equal to the ratio of acoustic conversion efficiency, the area ratio of t[32, 3r-4r-2 3, . . . , 3r is 2. 2.

Set it so that it becomes 2.

However, in such a method, the area ratio of each signal electrode constituting the acoustic conversion units (Nl to Nr) increases from the inner circumference to the outer circumference in the form of a power of 2.
There was a drawback that the shape had to be very large for input signals with a large number of pits. For example, in the case of 16 bits, the area ratio between the electrode of the smallest bit and the electrode of the largest bit is actually 32,768 times. Furthermore, in such a method, it is extremely difficult to accurately set the conversion efficiency of each acoustic conversion unit, and there is a drawback that distortion occurs in the restored acoustic signal.

[Summary of the invention]

The present invention has been made for the purpose of solving the above-mentioned drawbacks of conventional acoustic transducers, and includes providing a weighting amplifier in a drive circuit for driving an acoustic transducer unit.

[Embodiments of the invention]

First, in order to facilitate understanding of the present invention, the principle of a drive circuit for an acoustic transducer will be explained.

Generally, the imaging plate constituting the acoustic conversion unit is designed to be located at the center of the imaging area.

Therefore, in a digital acoustic transducer that directly applies a PCM acoustic signal to the acoustic transducer unit, the driving PCM signal only gives displacement in the positive direction.
It is necessary to convert a digital signal with a value of (0/1"l) into a digital signal with three values (-110/1) that can provide displacement in both positive and negative directions.

FIG. 2 shows a principle diagram for this purpose.

In the figure, each input terminal II to Ir is connected to SM (SIGN,
It is assumed that a binary digital signal of mGNtTtrng ) format is added. At this time, since the most significant bit (MSB) is the sign bit, the polarity of the input signal is determined using the MSB, and the output is obtained by multiplying each input bit signal by the positive or negative power supply voltage whose polarity has been determined. It will be converted into a ternary digital signal. This digital signal is applied bit by bit to each signal electrode 32 to 3r of the acoustic conversion units N2 to Nr.

Figure 3 shows a concrete realization of the conversion circuit based on the principle of Figure 2 using logical operation elements, and furthermore, the output signal is weighted via an amplifier for acoustic conversion. 32 to 3r, an embodiment of the acoustic transducer of the present invention is shown. In the figure, 1 is an inverter and 2a.

2 b , 3 a , 3 b , ---, ra
, r b is an AND circuit, 12.13. ..., 1r
are subtracters consisting of operational amplifiers T, 22, 23 . ...,
2r is a weighted amplifier, 30 is a ground electrode terminal provided on the entire back surface of the electroacoustic transducer, 32, 33. ...
, 3r are signal electrodes provided on the surfaces thereof, 42, 43 .
..., 4r is the output voltage of the binary to ternary conversion circuit.

Now, in Figure 3, when the digital signal is input manually,
Output voltages 42, 43 of the conversion circuit. ..., 4r, when MS a=r OJ (positive polarity), each bit signal is output as is, MSB = "1" (negative polarity)
When , the polarity is inverted and output. In this way, the digital input signal is converted from a binary to a ternary digital signal, and the weighting is performed by the amplifiers 22, 23, . . . , 2.
The voltage is amplified and output at r, and each acoustic conversion unit)N
2 to Nr are applied to the electrodes 32 , 33 , . . . , 3r. Here, the applied voltages are E2, E5+...
Er, each electrode 32, 33 . ...
, 3r conversion efficiency is 112. η5. ..., ηr, the weighting used in the acoustic transducer of the present invention is the amplification degree of the amplifier, each conversion efficiency η2. ηuh...,ηr
and applied voltage E2. E5.・ , product η2E2 with Er,
The ratios of η5E5, ..., ηrBr are set to be 21r-z, i2, ...12. By doing this, for example, each signal electrode 32°33
,...,3r, there is a limit to the area that can be obtained, and the acoustic conversion efficiency is 21.2, as in the case of Fig. 1,...
It is possible to operate as a digital acoustic transducer even if the ratio is not 2. If we think about this in reverse, it shows that even when configuring an acoustic transducer with a limited size, there is a degree of freedom in setting the area of the signal electrode, and for example, even the signal electrode of the least significant bit can have a sufficient area. However, it has the advantage of being easier to assemble. Furthermore, the applied voltage E2 to each signal electrode
゜E5. ..., Er is weighted by fully adjusting the amplification degree of the amplifier, '72E21η3E5.・・・・・・
・.

Since the ratio of ηrEr can be set with high precision so that the ratio t-2, 2, .

〔Effect of the invention〕

As explained above, this invention includes a conversion circuit for converting a binary digital signal into a ternary digital signal and a weighting amplifier for weighting the ternary signal. It has the effect of keeping its shape to an appropriate size and restoring an acoustic signal with less distortion.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an example of a conventional electroacoustic transducer, Fig. 2 is a principle diagram of a conversion circuit for converting a binary digital signal into a ternary digital signal, and Fig. 3 is an acoustic transducer according to the present invention. FIG. 2 is a circuit diagram showing an example of a conversion device. 1-...Inverter, 2a, 2b, 3a, 3b, ---
, ra, rb*a*AND circuit, 12, 13+ ・L
, 1 ra @ I subtractor, 22 , 23 , .
2 r... Weighting is amplifier, 30... Earth Army Extreme 1st child, 3.2, 33. ..., 3r... Signal Denzuka, 42.43. ..., 4r-φ conversion circuit. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent Masuo Oiwa (and 2 others) Figure 2

Claims (2)

[Claims] (1) Equipped with a conversion circuit that converts a binary digital signal into a ternary digital signal and an amplifier that amplifies each of the ternary digital signals, and output voltage E 2 of each amplifier,
E 5,−, E r (r is an integer) is composed of at least an electric sensor and a signal electrode, and the acoustic conversion efficiency η2. η
An acoustic transducer configured to apply the voltage E2 to each of the acoustic transducer units . E
U..., Er and conversion efficiency η2. η5. ..., ηr
The product E2・η2. An acoustic transducer characterized in that the ratio of the values of E5η, . . . , Erηr is set to a predetermined value. (2) Product E2-t)2. f15η5. -ETt)r, the ratio of each value is 2. The acoustic transducer according to claim 1, wherein the acoustic transducer is set to 2, ..., 2.