JPH0523324A - Exhalation current sensor - Google Patents

Abstract

PURPOSE:To achieve higher detection sensitivity of an exhalation current by setting an amplification factor distribution of a plurality of microphone units according to a flow rate of exhalation. CONSTITUTION:Electric signals which are generated in microphone units 5a, 5b and 5c by an exhalation current hitting a front plate 2 of an external box 1 are amplified separately in a ratio of a resistance 24 to a resistance 23a, in the ratio of the resistance 24 to a resistance 23b and in the ratio of the resistance 24 to a resistance 23c and addition outputs of the signal appear at an output terminal 26. Thus, the detection sensitivity of a exhalation current can be improved by setting the resistances 23a, 23b and 23c to an optimum ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a call flow sensor for use in a speech utterance training machine or the like.

[0002]

2. Description of the Related Art FIG. 2A is a sectional view showing the structure of a conventional expiratory flow sensor. In the figure, 1 is an outer casing, 2 is a front plate which is a front portion of the outer casing 1, 3 is a sound hole provided in the front plate 2, 4 is a front air chamber, and 5 is a bottom face of the front air chamber 4. 6 is a lead wire of the microphone unit 5, 7 is an electronic circuit portion, and 8 is a cord for connecting the call airflow sensor to another.

FIG. 2B is a circuit diagram of a main part of the expiratory flow sensor. In the figure, 11 is a field effect transistor for impedance conversion, 12 is a load resistor, and 13 is an amplifier.

FIG. 3 is a side view showing an example of use of the exhalation airflow sensor. The expiratory flow sensor is used to detect plosive sounds at the time of vocalization of squeaking noises such as pasal sounds, tassing sounds, and kasou sounds in training of vocalization and speech.

One microphone unit has been used in the conventional exhalation airflow sensor. In FIG. 2A, the exhalation airflow of the speaker enters the front air chamber 4 through the sound hole 3 formed in the front plate 2. Since the expiratory flow is an extremely low frequency component lower than the voice band, the front air chamber 4 is provided as a mechanical means for removing the unnecessary voice band. The exhalation airflow entering the front air chamber 4 is converted into an electric signal by the microphone unit 5, passes through the lead wire 6, and is amplified by the electronic circuit section 7.

[0006]

However, the above-mentioned conventional expiratory flow sensor is effective for high-speed pacing noise with a large expiratory flow rate, but is sufficient for other sounds because the expiratory flow rate and flow velocity are small. There was a problem that such output could not be obtained.

The present invention is intended to solve such a conventional problem, and an object thereof is to provide an excellent expiratory flow sensor capable of detecting a squeak noise having a small expiratory flow rate or flow velocity.

[0008]

In order to achieve the above object, the present invention is provided with an adder circuit for adding the outputs of a plurality of microphone units arranged at the bottom of the front air chamber, so that the expiratory air flow spreading over a wide range from the mouth is provided. For the purpose of detection, the addition circuit has a function of changing the addition coefficient of the microphone unit in the portion where the exhalation airflow is hard to hit.

[0009]

According to this structure, by adding the respective output signals of the plurality of microphone units, it is possible to enhance the detection sensitivity and detect even when the expiratory flow rate and the flow velocity are small, and the addition coefficient of each microphone unit is added. It is possible to detect even when the exhaled airflow hits the end portion of the front plate of the outer casing by changing.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1A is a sectional view showing the structure of an embodiment of the present invention. In the figure, 1 is an outer casing, 2 is a part of the outer casing 1, and is a front plate which is inwardly projected, 3a, 3b and 3c are sound holes formed in the front plate 2, 4 is a front air chamber, 5a, 5b,
Reference numeral 5c denotes a microphone unit which is brought into close contact with holes formed in the bottom surface of the front air chamber 4 corresponding to the sound holes 3a, 3b and 3c, 6
Is the lead wire of the microphone units 5a, 5b, 5c,
Reference numeral 7 is an electronic circuit section for signal processing the outputs from the lead wires 5a, 5b, 5c, and 8 is a cord for connecting the call airflow sensor to another. A is the direction of the expiratory flow.

FIG. 1B is a circuit diagram of a main part of this embodiment. In the figure, 5a, 5b and 5c are microphone units, and show examples of electret condenser microphones.

Reference numerals 21a, 21b and 21c are field effect transistors for impedance conversion, and 22a and 22c.
b and 22c are load resistors of the transistors 21a, 21b and 21c, 23a, 23b and 23c are resistors for connecting signals, 24 is a negative feedback resistor, 25 is an operational amplifier, 26
Is the output terminal of the operational amplifier 25.

Next, the operation will be described. When the exhalation airflow hits the front plate 2 of the outer casing 1 as shown by an arrow A, the microphone unit 5a mainly corresponding to the sound hole 3a detects the exhalation airflow and generates a signal voltage. A signal whose output is converted to low impedance through the field effect transistor 21a appears at both ends of the load resistor 22a. This is input to the "-" terminal of the operational amplifier 25 through the resistor 23a. The amplification degree of the operational amplifier 25 becomes equal to the ratio of the value of the resistor 23a to the value of the resistor 24 by the negative feedback resistor 24. Similarly, the degree of amplification of the output signal of the microphone unit 5b in the operational amplifier 25 is the resistance 2 with respect to the value of the resistance 24.
The ratio of the value of 3b and the amplification degree of the output signal of the microphone unit 5c in the operational amplifier 25 become equal to the ratio of the value of the resistor 23c to the value of the resistor 24. Output terminal 26
The signals appearing at are the above three microphone units 5a,
The output signals of 5b and 5c are added. In this way, the signals detected by each of the microphone units 5a, 5b, 5c are added to form an output signal, so that the resistance 23
In setting a, 23b, and 23c, the addition coefficient is changed by setting the amplification degree of the microphone unit output signal arranged at the end portion of the front plate with a small expiratory flow rate to be larger than the amplification degrees of the other microphone unit output signals. Since the addition is made, there is an effect that it is possible to detect even a minute exhalation airflow hitting the end portion of the front plate.

There are two ways to set the amplification factor distribution of each microphone unit, that is, that all the products are made uniform during the manufacture of the call airflow sensor, and that the settings are adjusted according to the individuality of the subject at the time of use. Is also effective.

[0015]

As is apparent from the above embodiment, the present invention provides an expiratory flow sensor in which a plurality of microphone units are arranged so that the signal amplification of each microphone unit is set according to the expiratory flow rate. The detection sensitivity can be improved.

[Brief description of drawings]

FIG. 1A is a sectional view of an exhalation airflow sensor according to an embodiment of the present invention. FIG. 1B is a circuit diagram of a main part of the exhalation airflow sensor.

FIG. 2A is a sectional view of a conventional exhalation airflow sensor. FIG. 2B is a circuit diagram of a main part of the exhalation airflow sensor.

FIG. 3 is a side view showing a usage state of the exhalation airflow sensor.

[Explanation of symbols]

 1 Outer casing 2 Front plate 3a-3c Sound hole 4 Front chamber 5a-5c Microphone unit 7 Electronic circuit part 21a-21c Field effect transistor 22a-22c Resistor 23a-23c Resistor 24 Resistor 25 Operational amplifier 26 Output terminal

Claims (1)

Claim: What is claimed is: 1. A front air chamber having a front plate having a plurality of sound holes and a bottom surface having a plurality of microphone units.
An expiratory flow sensor comprising: an addition circuit capable of changing an addition coefficient for adding the output signals of the microphone units.