JPH0228157B2 - ONATSUHENCHOSOCHI - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sound pressure modulation device that modulates sound pressure using a transducer.

Taking the alarm circuit of an electronic watch as an example, a conventional sound pressure modulation device outputs an audible frequency signal obtained by dividing the reference signal output from a crystal oscillator, that is, the duty is constant (usually the duty is 0.5).
The signal output of , and the multiple divided outputs obtained by further dividing this audio frequency signal output are input to a predetermined gate circuit, and the intermittent signal output from this gate circuit is input to the transducer. I was using the following configuration. This type of sound pressure modulation device changes the pulse width in a frequency range wider than the above-mentioned audible frequency, so it has the disadvantage that the sound pressure is constant and only intermittent output can be obtained.

The present invention corrects the above problems,
A sound pressure modulation device that synthesizes an audio frequency signal and multiple signals with higher frequencies using a gate circuit, changes the duty ratio of the audio frequency waveform, and modulates the sound pressure by applying this audio frequency signal to a transducer. It provides:

First, the principle of sound pressure modulation in the sound pressure modulation device of the present invention will be explained based on the drawings.

FIG. 1 shows the waveform of an audio frequency signal obtained by frequency division from a reference signal source including a crystal oscillator. When such a rectangular wave signal is applied to a transducer, the sound pressure as the output, that is, the intensity of the sound can be determined as being proportional to the amplitude value of the Fourier transform of the input rectangular wave.

The waveform in FIG. 1 is expressed by the following equation.

₍ x) = {a | x | < x ₀ /2, a is a constant o x ₀ /2≦ | /2+ _∞ 〓 ⁿ⁼¹ sin(nx ₀ /2)/nx ₀ /2cos nx] n is the fundamental wave (n=1), second harmonic (n=2), and third harmonic obtained by substituting integers. Each amplitude value of the harmonics (n=3) is set to a duty ratio of 0.5 in the fundamental wave (n=1).
This shows the relationship between amplitude and duty ratio, normalized based on . Looking at the relationship shown in the second diagram, it can be seen that by changing the duty ratio of the input waveform, the transducer output sound pressure corresponding to the fundamental wave and each harmonic can be changed.

FIG. 3 shows the relationship between the output sound pressure and the input frequency in a narrowband transducer that has a resonance point near the frequency of the input wave _{, 0} . When a transducer with the characteristics shown in Fig. 3 is excited by inputting the rectangular wave signal shown in Fig. 1, the transducer output sound pressure is expressed in almost the same shape as a sine wave curve with respect to the duty ratio of the input wave. . FIG. 4 shows this. That is, the harmonic components are removed and only the sound pressure that substantially depends on the fundamental wave is output.

The present invention will be explained in detail below based on the drawings.

FIG. 5 shows an alarm sound generation circuit for an electronic timepiece as an embodiment of the present invention. In Fig. 5, 1 is a crystal oscillator circuit, 2 is a frequency division ratio of 1/l (l is an integer) with the output pulse of the crystal oscillator circuit 1 as input.
A first frequency divider circuit 3 receives the output pulse (1/l frequency divided signal) of the first frequency divider circuit 2 and further divides the frequency of the first frequency divider circuit 3. A second frequency dividing circuit for dividing the frequency into a low-order signal with a ratio of 1/m (m is an integer), 4 inputs the output F of the 1/m frequency divided signal end of the second frequency dividing circuit 3. It is a frequency dividing circuit with a frequency division ratio of 1/n (n is an integer), and 6
9 are control circuits which input a plurality of output pulses E and F obtained from the intermediate stage and the final stage of the second frequency dividing circuit 3, respectively, and form desired control signals. The function of the control circuit is to appropriate the timing of sound pressure modulation and the timing for generating alarm sounds in chronological order. 10～
14 is a binary signal drawn out from each stage of the first frequency dividing circuit 2, which is formed by the control circuits 6 to 9 with output pulses A, B, C, and D as shown in FIG. 6 as one input. output pulse L,
It is a logic synthesis circuit using gates with M, N, and S as the other inputs, and works as a waveform synthesis circuit. 15
16 is a transistor driven by the output pulse of the gate 14, and 16 is a transducer excited by the driving input supplied through the transistor 15 and for converting the output pulse signal of the gate 14 into sound. It has a narrow band with a resonance point near the frequency.

First, the output F obtained by sequentially dividing the reference oscillation output pulse of the crystal oscillation circuit 1 in FIG. The frequency is divided by 4, and the binary signals formed at each stage of the frequency dividing circuit 4 are sequentially taken out as outputs, and the outputs G, H, I, J, and K are passed through a logic synthesis circuit consisting of gates 6 to 8. Respective logical synthesis output pulses L, M, and N shown in FIG. 7 are obtained. These outputs L, M, and N define the timing of outputs of different sound pressures. The output pulses A, B, C, and D of the first frequency dividing circuit 2 are shown in FIG.
The output pulses O, P, Q and R modulated at the audio frequency shown in FIG. 7 are obtained through each gate of FIG.
By the way, the output waveform O in FIG. 7 uses the divided outputs G, H, I, J, and K of the frequency dividing circuit 4 as inputs
The output L of the NOR gate 6 and the divided outputs A, B, C, and D of the first frequency dividing circuit 2 are input.
It is the output waveform of the NAND gate circuit 10, and
O' indicates the repetitive state of the output signal during the H level period of the output L mentioned above.

The output waveform P is the inverted signal and the divided output of the frequency-divided output G of the frequency divider circuit 4, the output M of the NOR gate 7 whose inputs are H, I, J, and K, and the frequency division of the first frequency divider circuit 2. NAND with outputs B, C and D as inputs
This is the output waveform of the gate circuit 11, and P′ is
It shows the repeated state of the output signal during the H level period of the output M described above.

The output waveform Q is the divided output J of the frequency dividing circuit 4.
Input the outputs L and M of NOR gates 6 and 7.
NAND gate circuit 12 whose inputs are the output N of the NOR gate 8 and the frequency division output D of the first frequency division circuit 2
, and Q' is the output waveform of the above output N
This shows the repeated state of the output signal during the H level period.

Furthermore, the output waveform R is the NAND gate circuit 1
This is the output waveform of the NAND gate 13 which receives the outputs O, P and Q of outputs 0, 11 and 12 as input, and O'', P'' and Q'' are the repetition of the output signal during the H level period of the above output R. The waveforms of the outputs O, P, Q, and R, when viewed in terms of audible frequency, correspond to O', O', and R shown in FIG.
Each of the P′ and Q′ parts has the same period T ₁ as the audible frequency D, only the duty, O′ is 0.0625, and P′ is
0.125, Q' is 0.5, and three different types of audio waves are formed. Furthermore, the divided outputs E and F of the second frequency dividing circuit 3 are input to the NAND gate circuit 9 to obtain the time-intermittent output pulse S shown in FIG.
When input to the OR gate circuit 14, a time-intermittent output pulse T modulated at an audio frequency is obtained at its output terminal. O″ shown in Figure 8 of the output T,
The waveforms that represent the P″ and Q″ portions in terms of the audible frequency are O″, P″, and Q″ in Figure 9.The waveforms of each of these O″, P″, and Q″ are at the audible frequency D It is an audible frequency that has the same period T ₁ as , but differs only in the duty ratio.

This output pulse T is applied to the transistor 15, which causes the transducer (buzzer) 16
When excited, the sound pressure at parts O″, P″, and Q″ shown in Figure 8 will be the amplitude values of the Fourier transform of the waveforms O″, P″, and Q″ shown in Figure 9, that is, the sound pressure shown in Figure 4. is approximately proportional to the amplitude of each duty ratio corresponding point,
Therefore, the output of the circuit shown in FIG. 5 can be heard as an output whose sound intensity changes in three stages over time.

As described above, according to the sound pressure modulation device of the present invention, since the sound pressure is modulated by changing the duty ratio of the audible frequency, it is possible to change the sound pressure in a time-series manner even for continuous sound, which conventionally could not be modulated in sound pressure. Furthermore, sound pressure can be efficiently modulated by removing harmonic components using a narrowband transducer.

[Brief explanation of drawings]

Figures 1 to 4 are diagrams for explaining the principle of the present invention. Figure 1 is a diagram showing a rectangular wave with a duty ratio of 0.5, and Figure 2 is a diagram showing changing the duty ratio of the rectangular wave in Figure 1. Figure 3 is a characteristic diagram of a narrowband transducer, and Figure 4 is the input of the same transducer. 5 is a diagram showing the relationship between the duty ratio of a square wave and the output sound pressure, FIG. 5 is a diagram showing the circuit configuration of a sound pressure modulation device for alarming an electronic clock according to an embodiment of the present invention, FIGS. 6 and 7 , FIG. 8 is a diagram showing signal waveforms at each point of the circuit shown in FIG. 5, and FIG. 9 is a diagram showing partial waveforms of output pulses shown in FIGS. 7 and 8. 1... Crystal oscillation circuit, 2... First frequency dividing circuit,
3...Second frequency divider circuit, 4-9...Control circuit composed of frequency divider circuit 4 and gates 5, 6, 7, 8, 9, 10-14...Waveform synthesis composed of gates Circuit, 15...Amplifying transistor, 16...Transducer (buzzer).

Claims (1)

[Claims] 1 a first frequency dividing circuit that divides a reference signal from a signal source to obtain a plurality of divided signals of an audio frequency and at least one frequency higher than the audio frequency;
a second frequency dividing circuit that divides the signal of the frequency dividing circuit into a frequency signal having a frequency lower than the audio frequency, and logically synthesizes the plurality of frequency divided signals including the audio frequency to determine the duty ratio of the audio frequency waveform. and a narrowband transducer having a resonant frequency at or near the audible frequency, and time-series or time-intermittent sound pressure generation depending on the signal of the second frequency dividing circuit. A sound pressure modulation device characterized by forming a signal.