JPS5966293A - Noise-proof telephone set - Google Patents

Abstract

PURPOSE:To attain the release of both hands and to prevent the reduction in speech quality due to side tone noise, by mounting the ear piece of a handset to an ear. CONSTITUTION:In case of transmission, the sound pressure of voice is produced from an ear T3 into an air-tight chamber C, diaphragms T1, T2 are driven and currents I1, I2 are produced in circuit. A discriminating circuit Bc discriminates transmission or receiving by amplifying the currents I1, I2 and obtaining the ratio of the currents I1, I2 at an electronic circuit Br. The gain of amplifiers K1, K2 is taken negative or positive for the transmission and it is taken inversely positive or negative for the receiving. Thus, a telephone set for one-ear transmission/receiving is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a noise-proof telephone that uses one electroacoustic transducer to serve as both a transmitter and a receiver.

With a normal telephone, the person making the call holds the handset with one hand, so only one hand is free. Furthermore, when talking in a noisy place, the intelligibility of the call is significantly reduced due to interference from sidetone coming from the talker's transmitter.

In the telephone of the present invention, a transmitter and a receiver are attached to the same earpiece, which is worn on one ear, and an acoustically airtight chamber is formed between the earpiece and the ear. The resulting sound pressure is received by the transmitter, and its electrical output is corrected for frequency characteristics and amplified before being transmitted, and the gain of the receiver amplifier is reduced, that is, thicker attenuation is provided. When receiving a call, the gain of the receive amplifier is increased and at the same time the gain of the transmit amplifier is lowered to attenuate the transmit power.

In this case, the telephone circuit is controlled by determining whether to send or receive a call based on the ratio of the output of the sender and the human power of the receiver. Therefore, by using earplugs, etc., both hands are free, and by installing the transmitter in an airtight chamber, external noise is prevented from entering the transmitted voice, and communication interference due to sidetone noise is significantly reduced.

The principle of the present invention will be explained below with reference to FIG. .

The figure is an isometric diagram showing the acoustic part of the telephone according to the present invention, where T1 is the operating position, T2 is the transmitter, llTm,
'l: 11 o'clock.

Isometrically the ear is 1 and it is set to 0 again? 'Knee h':'
T...

T2 + Tg is a reversible air-sound i converter, which is installed in an airtight chamber C as shown in the figure. For such a system, the following relationship holds. '1") S, i + jωξノOT"" At, Ij
,・”−””””””””””Da・ (1) Here, ρ
: Sound pressure v in 0 : Valley shape of C □ : Bulk modulus of elasticity ω of gas in C : Angular frequency A- : Fuss factor of Tl 82.3 is 'I't, T2. Ts d corresponding S
・: Effective area of the diaphragm i: Mechanical impedance of the vibration system ξ ・: Displacement of the diaphragm EL: External electromotive force of the circuit of 'r, 2E: Impedance of the circuit of ゛rλ: IL of the circuit of T< When making an electric current call, when you speak, a sound is emitted from your ears and your ears -□
A sound pressure is generated within the distance. This is Karasuki O1 in Figure 1.
, Bl:′〒rc2. ．． This corresponds to setting =o.

+[, is used as a receiver and TI as a transmitter, and It / It is expressed as the expression "(1i, "(2), (3
), then .

In particular, if we use the same electroacoustic transducer for 'I'l*, %, then A+ = At , Sr = St l , )l
= 7t ”+ Z, 1=Z*”': (α,
1), =/ ・・・・・・Bottom・・・・・・・・・
・・Cliff・・・・・・・・・・・・・・・・ (u
a) Next, use TI as a receiver and □T as a transmitter,
Considering the case of receiving a call, in this case, BK01B2=E
, -0, so input (11, (2J, L from (3)
/It is found here: As before, if T1 and T are the same electric sound/□acoustic transducer, then α, is, □Apply the above theory to telephone transmission, reception, and speech. When a person speaks, the sound is radiated from the lips to the outside, and in a normal telephone, the voice is received by a transmitter placed just before the lips, and is converted into an electrical signal and transmitted. The caller must maintain a strong grip on the handset with one hand, and external noise can freely enter the handset. Naturally, this noise causes a deterioration of speech quality by 1 as noise to the other party, but when listening to what the other party is saying, it becomes a noise interference due to sidetone, resulting in a significant drop in intelligibility. This is often experienced when talking from a public phone in a crowded place or a machine shop with a lot of noise. When a person speaks, the sound is also radiated from the ears.

The voice that comes out of the ear is attenuated as it travels from the mouth to the ear.
Its frequency ic9. Although the characteristics have been slightly distorted,
This distortion can be compensated for by the characteristics of the amplifier, so the frequency characteristics of the voice sent from the telephone to the line are almost the same as the telephone output due to the voice coming from the lips.

As shown in FIG.
; When Jin is removed and attached, the transmitter T! The middle power of the sound is transmitted to the receiver through the sidetone circuit, and it is necessary to reduce this influence. .

, Seven Day Gin, transmitting and receiving gain of the transmitting circuit and the receiving circuit cr>
, it is necessary to control according to the situation. An example of the circuit No. 7 is shown in FIG.

In the figure, K is a receiver amplifier, and K is a transmitter amplifier, the gain of which is controlled over a wide range from - to 10 by the control output of the discrimination circuit B0. K, ,' K2 is...
1' To the handset/time @':'n to the receiver 3, child, transmitter terminal □
inserted. □ When transmitting a call, a sound pressure of voice □ is generated from the ear T3 at zero height in the airtight chamber. This sound pressure drives the □ diaphragms of TI and T't. Both El + By are O. T
1+T, produces a current I, ,I, in the circuit. This current value is amplified by amplifiers B1 and B, and L is
Find /It and determine whether this I, /I, has the value of equation (4) or (4'a), or whether it has the value of equation (5) or (ja).
By determining whether the telephone has a value of 3c, it is determined whether the telephone is transmitting or receiving, and when transmitting, a gain of 1 is set to the amplifier as a negative value, and a gain of 2 is set to the amplifier. In the case of receiving a call, conversely, the gain of 1 is positive and the gain of K2 is negative. Switching between sending and receiving calls involves a delicate problem in terms of call quality, so controlling the amplification gain requires a slight modification from the value shown in the formula, but by performing the control described above, it is possible to A telephone for receiving calls can be realized.

In such telephones, by attaching the earpiece of the handset to the ear like an earphone,
The caller's hands can be freed. Furthermore, as is clear from the above, since external noise does not enter the transmitter, deterioration in speech quality due to sidetone noise can be prevented.

[Brief explanation of drawings]

FIG. 1 is an isometric diagram showing a system in which three electroacoustic transducers are acoustically coupled, and the diagram at the bottom shows a telephone circuit according to an embodiment of the present invention. T11% + Tl: Reversible electroacoustic transducer, C2 acoustic airtight chamber, K: Receive amplifier, K2: Transmit amplifier, B
c: discrimination circuit, K: filling machine circuit, Dl, 13. :
Amplifier of transducer T1+T1 respectively, Br: II/
Iv '16'' electronic circuit. Patent applicant: Japan Communication Technology Co., Ltd. 1':4゜Representative name: Yoshi Ito i1.・Pa□'-.

Claims (1)

[Claims] Two electroacoustic transducers are attached to seven earpieces, and when making a telephone call, the earpiece is placed in one ear to form an acoustically airtight chamber between the earpiece and the ear. Using an acoustic transducer as a transmitter and another electroacoustic transducer as a receiver, the ratio of the electrical input to the receiver and the electrical output of the receiver determines whether a call is being made or is being received. A noise-proof telephone set is characterized in that it determines whether or not the telephone is in use and controls a telephone call circuit.