JPS6021695A - Reproducing device of pulse code modulating signal - Google Patents

Abstract

PURPOSE:To attain the acoustic reproduction utilizing the nonlinear parametric operation of air by reproducing a pulse code modulating signal by an ultrasonic wave element. CONSTITUTION:A signal subject to pulse code modulation from an input signal 1 at an A/D converter 2 is formed as 4 bits; signals 5-8 in order from the lower bit. An oscillator 4 has an oscillating frequency nearly equal to the resonance frequency of ultrasonic wave elements 21-24. The signal of the oscillator 4 and the signals 5-8 are processed for operation by multipliers 9-12. The signals subject to processing operation are amplified by amplifiers 13-16 and the weighting depending on each bit is conducted by level control elements 17-20. The resonance frequency of the ultrasonic wave elements 21-24 and the reference frequency (the frequency of the oscillator 4 in this case) included in the signal 5-8 are set nearly equal by applying the signals to the ultrasonic wave elements 21-24.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pulse code modulation reproduction speaker.

MS of signals converted from conventional analog signals to digital signals
A speaker that uses an acoustic transducer that supports signals from B to LSB is being proposed. In this case, the number of acoustic transducers required for playback corresponds to each bit, which has the disadvantage of complicating the equipment.If multiple coils are attached to the bobbin of one transducer, the conversion efficiency will decrease due to the increased mass. It has the disadvantage of decreasing.

The present invention provides a novel device which solves the above-mentioned drawbacks and is achieved by utilizing the non-linear parametric action of air.

The present invention will be explained by way of an example.

FIG. 1 is a diagram showing an embodiment of the present invention, in which input signal 1 is
The signal pulse code modulated by the D converter 2 is 4 bits,
Signals 5, 6°, 7.8. Indicated by The oscillator 4 has an oscillation frequency approximately equal to the resonant frequency of each of the ultrasonic elements 21.2.2.23.24. The signal of the oscillator 4 and the signal 5.6.7.8 are multiplied by the multiplier 9.10.1.
1. Perform calculation processing in 12.

The processed signal is sent to amplifier 1.3.14.15.16
The level control elements 17, 18, and 20 perform weighting according to each bit.

By applying a signal to the ultrasonic elements 21, 22, 23, 24, the resonant frequency of the ultrasonic element and the reference frequency included in the signal In this embodiment, the frequency of the oscillator 40 is set to be approximately equal. Then signal 5.6.7.8 as per figure 2
b'l is the LSB, b2゜b3 and the MSB, respectively.
is converted into a 4-bit parallel signal as b4. On the other hand, the valve vibrator 4 outputs an ultrasonic frequency sine wave signal d, and the multiplier 9.10. When the calculation is performed in '11.12, each output has 'di, d2. d3. Obtain the d4 signal.

When each pitch is weighted accordingly and applied to the ultrasonic elements 21', 22, 23, and 24 of the acoustic transducer, the sound waves from each element are radiated in phase, and the air vibrates with a waveform of e. do.

If the envelope of a sound wave is 7 (71), it is expressed by this waveform element.

However, is the resonance angular frequency of the ultrasonic element.

This produces a secondary sound pressure of

However, γ is the distance between the ultrasonic element and the sound receiving point, C is the speed of sound, and K is a constant determined by air density, nonlinear constant, etc.

7 (It is easy to understand that h is a sine wave like a, but the secondary sound wave has an envelope (t) of 0. If the harmonic component of 3 is ignored, the waveform that can be heard at the extreme becomes ÷. This is equal to the original input waveform a.

However, in this case, the amplitude modulation index shown in Figure 7 is considered to be 1. In order to reduce this, it is possible to emit a sound wave containing only ultrasonic components from one or all of the ultrasonic transducers, and it is necessary to provide a separate ultrasonic transducer for this purpose. good.

Also, level control element 17.18.19.20
Ultrasonic element 2.1.22゜2 without weighting by
It is also possible to use input characteristics corresponding to the input characteristics of 3 and 24 for each pitch.

Since each bit is arranged in parallel and acoustically converted, a vibrating element with a high resonant frequency can be obtained. It is also possible to create and modulate an ultrasonic vibration frequency by 1ffit calculation processing that matches the resonance frequency of each acoustic transducer element.

FIG. 3 is a diagram showing another embodiment of the present invention, in which a multiplier 9.
After weighting the outputs of 10, 11, and 12, they are combined by an adder 34, amplified by an amplifier 33, and acoustically converted by an ultrasonic transducer 35. In this case, only one amplifier can be used.

FIG. 4 is a diagram showing another embodiment of the present invention, in which the signal from the oscillator 4 is transferred to the level control element 36 in the configuration shown in FIG.
A configuration is shown in which the level is adjusted and added to the adder 34 as a bias amount.

Since the level is adjusted by the level control element 36, adjustment using a single element is possible when adjusting to the non-linear characteristics of air.

The ultrasonic element 35 may be a single element or may be a combination of elements in an array.

Although the above explanation has been made using 4 bits, it is possible to increase or decrease the number of bits.

As described above, according to the present invention, by reproducing a pulse code modulated signal with an ultrasonic element, nonlinear parameters of air can be determined.
This makes it possible to reproduce sound using II racks.

[Brief explanation of drawings]

FIG. 1 is a diagram showing one embodiment of the present invention, FIG. 2 is a diagram for explaining waveforms of each part, and FIGS. 3 and 4 are diagrams showing other embodiments of the present invention. . 1...Input signal, 2...AD converter,
4...Oscillator, 5.6.7.8...Signal, 9.10.11. , 12... Multiplier, 13
．． 14.15.16.33...Amplifier, 17.
18.19.2 (1゜36... Level control element, 21.22.23.24゜35...
Ultrasonic device applicant: Nippon Columbia Co., Ltd. Agent: Kazumi Yamaguchi, patent attorney: 5) 5 houses/School 112

Claims (1)

[Claims] A pulse code modulated signal, which is characterized in that a signal obtained by pulse code modulating an input signal and processing it is applied to a speaker that utilizes the nonlinear parametric effect of air, and the reference frequency included in the signal is made approximately equal to the resonant frequency of the speaker. playback device.