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BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is capable of
listening to stereo sound from the handsets such as the left and right headphones and earphones
when listening to stereo, and when communicating by telephone, it is possible to communicate
with a microphone that is a microphone. The present invention relates to a stereo, telephone
switching transmission / reception device in which telephone communication can be performed
clearly by eliminating the voice from one handset close to the transmitter and using only the
voice from the other handset.
2. Description of the Related Art In recent years, personal computers have been on the market
with great momentum, as it is said to be one in any family, and accordingly, computers
themselves are also multi-functionalized, and it is also possible to view compact discs and
televisions. In addition, a telephone line has also been connected to perform personal computer
communication and FAX communication, and at the same time, a device having a function as a
telephone has been developed.
By the way, if you receive a call while using a computer like this to listen to a compact disc or
television audio with a stereo receiver such as an earphone or a headphone, you can listen to the
stereo receiver from your ear I will take it off by hand and pick up the handset of my telephone
and place it on my ear to make a call.
In other words, there is a problem that the user must disconnect the stereo handset and hold the
handset of the telephone at another place to make a telephone call.
Therefore, it is considered to use a commercially available hands-free handset for a mobile phone
(one with a receiver and a transmitter integrated) to enable two listeners to listen to a stereo. Be
In this case, the two handsets listen to the stereo, and in the case of a telephone, the hands-free
type handset can make a call, so it is possible to make a hands-free call without having to
disconnect the stereo handset even during the work.
However, in order to make a call with the above-mentioned hands-free type handset, the voice of
the call from the handset leaks to the transmitter side, causing howling and clarity to the
telephone call. There is a drawback that the problem arises that it becomes difficult to
communicate with the other party.
In addition, since the handset is worn near the ear, the volume is lower than taking a voice in
front of the mouth, and the reduction of the volume is compensated by the amplifier so that
ambient noise and ambient echo are easily picked up.
Therefore, a short-shaped, highly directional transmitter and an ambient noise suppression
circuit are required.
The present invention is intended to solve the above-mentioned problems, and the object of the
present invention is to switch between switch means so that it can be listened to by two receivers
when listening to a stereo, and integrated with a transmitter when making a telephone call In
order to listen with the other handset, it is intended to provide a stereo telephone switch /
transmission / reception device that can increase the intelligibility of calls without any fear of
howling since there is a sufficient distance between the handsets. .
SUMMARY OF THE INVENTION According to the present invention, there is provided a telephone
switching transmission / reception device which achieves the above object, and the means
comprises first and second handsets connectable to a stereo device; A transmitter mounted close
to the handset of the receiver, a transmitting / receiving circuit which is a telephone set to which
the handset and the second handset can be connected, the stereo device and the first and second
handsets when listening to a stereo And a switch means for connecting the transmitter and the
second handset at the time of telephone call.
Preferably, the switch means comprises a reception detection circuit for performing the
switching when the call signal from the transmission / reception circuit is received, and the
transmitter is integrally formed with the receiver. The bi-directional microphone is
accommodated substantially at the center of the cavity and the both ends are filled with a sound
absorbing material, or two unidirectional microphones are accommodated at both ends of the
Further, an ambient noise suppression circuit is connected to the transmitter, and the ambient
noise suppression circuit passes only the frequency of the specific frequency band of the AC
output from the transmitter and the gain controller having the AC output as an input. A peak
hold circuit comprising: a band amplifier to be driven; a peak detector for taking out an output
corresponding to the peak value of the AC output passed through the band amplifier; and a hold
circuit for suppressing the attenuation of the output level of the peak detector for a
predetermined holding time And controlling the gain of the gain controller according to the
output signal level of the peak hold circuit.
DESCRIPTION OF THE PREFERRED EMBODIMENT A personal computer 4 (hereinafter referred
to simply as a personal computer) to which a telephone line 3 of FIG. 1 is connected and a
handset 1 and a second handset 2 to be described later are connected. Will be described.
The personal computer 4 detects the input of the call signal to the telephone line 3 by detecting
the above-mentioned stereo device 4a, the transmission / reception circuit 4b connecting the
telephone line 3 and the personal computer 4, and the two circuits are normally closed. A
reception detection circuit 4d for controlling a relay 4c having a contact 4c1 and two normally
open contacts 4c2 is incorporated.
Then, a hands-free type handset in which a first receiver 1a, which is a speaker for listening to
stereo reproduction sound or for making a telephone call, is integrated with the personal
computer 4 into a transmitter 1b, which is a microphone. 1 and a second handset 2 consisting
only of earphones are connected.
Hereinafter, the handsfree handset 1 will be described with reference to FIG.
11 is a case formed in a substantially L-shape by a synthetic resin, and a bulging body 11a
having a size to enter the entrance of the ear canal is detachably attached to the receiver side
which is a short side of the L-shape. A cavity 11b is formed in the protrusion 11a, and a sound
emitting portion 11c is formed in the bulging body 11a.
Preferably, the case 11 is made of an integrally molded product of plastic such as ABS resin.
In addition, on the side of the transmitter which is one long side of the case 11, a longitudinally
elongated hollow portion 11d having both ends opened is formed, and an electret type
microphone having a directivity or a single directivity is formed substantially at the center of the
hollow portion 11d. A transmitter 1b in which two directional microphones are back-to-back is
Further, a net 12 is attached to the upper and lower openings of the hollow portion 11 d, and a
sound absorbing material 13 is accommodated between the transmitter 1 b and the net 12.
Further, the first receiver 1a, which is an electromagnetic speaker, is accommodated in the
hollow portion 11b of the bulging body 11a, and the sound from the first receiver 1a is emitted
only from the sound hole of the sound emitting portion 11c. Sound.
Reference numeral 14 denotes a connecting cord from the transmitter 1b and the receiver 1a,
which are led out through the outside of the hollow portion 11d in a state of being put together.
Further, the connection cords from the second handset 2 are put together in the middle of the
connection cord 14.
As the transmitter 1b, a small-sized, high-sensitivity electret microphone is optimum, and contact
noise of the connection cord 14 is also generated. Therefore, it is preferable to use a back
electret type in which it is difficult to pick up directly transmitted vibrations.
Next, the operation of the above-described handset 1 will be described.
First, the bulging body 11a of the case 11 is inserted and fixed in the pinna.
In this state, the shape of the sound emitting portion 11c is such a shape that does not
completely block the external ear canal, there is little feeling of obstruction and external sound
leaks and there is no problem in safety, and the sound from the sound emitting portion 11c
Leakage is also small.
In such a state, when an audio signal is input as an electrical signal from the connection cord 14
to the first receiver 1a, the audio is emitted from the receiver 1a, and the audio emitted from the
receiver 1a is a sound emitting unit It is emitted into the ear canal through the sound hole 11c.
On the other hand, the voice from the wearer is transmitted from the opening network 12 to the
transmitter 1b through the sound absorbing material 13, converted into an electric signal in the
transmitter 1b, and transmitted from the connection cord 14.
However, in the transmitter 1b, since the cavity 11d is close to the mouth of the wearer, the
sound level input from one end of the cavity 11d and the sound level input from the other end
are hollow. A delay occurs by the length of the portion 11d.
Therefore, the voice level of the wearer output from the transmitter 1b does not decrease so
On the other hand, external noise from a portion far from the wearer's mouth reaches the
network 12 at both ends in approximately the same signal level and in phase, so that it is
configured to be cut by the subtraction function of the two-way transmitter c. ing.
Therefore, when the noise source is separated, such as ambient noise, the sound wave of noise is
input in phase from both sides of the transmitter 1b, and as a result cancels and becomes
smaller, while the wearer's voice transmits Since the input from the lower side of the unit 1b is
closer to the mouth than the voice coming from above the transmitter 1b, it can be picked up as
a voice with sufficient sensitivity even if it is subtracted.
The lead wire to the first receiver 1a and the lead wire from the transmitter 1b are led out to the
lead accommodating portion 11e through a lead insertion pipe portion (not shown) formed on
the side surface of the case 11. It is integrated from the lead accommodating portion 11e and is
led to the outside.
In FIG. 3, the handset 1 described above is attached to one ear, and the other ear is attached to
the stereo receiver 2 of the earphone type, and FIG. 4 is a handset of the headphone type It is
attached to one of the handsets 1a of 1a and 2a.
In addition, 6 is a jack for inserting in plugs, such as a personal computer, and 5a is a box in
which the ambient noise suppression circuit 5 mentioned later is integrated.
Next, the entire operation will be described with reference to FIGS.
Now, when listening to music or the like from the stereo device 4a, the normally closed contact
4c1 is closed and the normally open contact 4c2 is opened as shown in FIG. I can listen to music.
In this state, when a call signal is input from the telephone line 3 to the transmission / reception
circuit 4b, the reception detection circuit 4d detects this and energizes the relay coil 4c.
Therefore, since the normally closed contact 4c1 is opened and the normally open contact 4c2 is
closed, the speech from the transmission / reception circuit 4b is sent to the receiver 2 through
one of the normally open contacts 4c2, and the transmitter 1b This voice is sent to the
transmission / reception circuit 4b through the other of the normally open contacts 4c2 so that a
call can be made.
At this time, since the receiver 1a integrated with the transmitter 1b is disconnected from the
transmitting / receiving circuit 4b and the distance between the receiver 2 and the transmitter
1b is sufficiently long, the voice from the receiver 1a is generated. There is no hindrance to the
telephone call and no howling with the transmitter 1b, so that the call can be made clear.
In place of the reception detection circuit 4d described above, a listener who knows that a call
has been made to the transmission / reception circuit 4b may be manually switched to make a
Next, since the transmitter 1b is separated from the mouth by 10 cm or more, the volume is
reduced by 10 dB or more, and amplification is performed to compensate for the amount of
As a result, using a nondirectional microphone makes it easier to pick up the ambient sound by
10 dB or more than the method of picking up the sound in front of the mouth.
In a computer environment, there are background music, noise for operating the keyboard, etc.,
and the echo of the room is also emphasized, so the ambient noise suppression of the transmitter
1b has to be virtually overcome.
In addition, in the transmitter connected to the transmission / reception circuit built in the
personal computer 4, both the voice of the caller and the ambient noise are converted into an
electrical signal and output.
Further, in the handset, a part of the signal from the self-sending device is added to the
communication signal transmitted from the other party to be converted into voice. That is, since
the caller can talk in peace by confirming the voice uttered by the receiver with the receiver, a
part of the transmission signal is added to the reception signal.
For this reason, when making a call under ambient noise, when listening to the other party's call,
it becomes very difficult to hear because the ambient noise from the automatic transmitter is
added to the other party's call. In addition, since the noise during the call is transmitted to the
other party and reproduced by the receiver, it is very unpleasant and it becomes difficult to
confirm the voice of the user and the conversation is disturbed.
Therefore, according to the present invention, the microphone 1b is a bi-directional microphone
housed in a pipe of 4 cm or more as shown in FIG. 2, and the ambient noise suppression shown
in FIG. The circuit 5 is connected, and a time zone in which only ambient noise is transmitted is
selectively taken out to suppress the transmission gain to substantially improve the transmission
SN ratio practically.
And the following two terms are mentioned as an important subject for aiming at the abovementioned improvement.
(1) It is easy and faithful to distinguish and detect vocal sections and silent sections. (2) The ratio
of the transmission gain of the voiced section to the unvoiced section (a section with only
ambient noise) is large. In order to satisfy the above problems, it is desirable to employ the
circuit of FIG. 3 as the transmitting and receiving circuit.
In FIG. 5, the transmitter 1b outputs the voice of the transmitter as an AC signal, the band
amplifier 51 passes a sound of 0.2 to 1 KHz or 0.2 to 2 KHz, and the sound 52 passes the band
amplifier 51. A peak hold circuit comprising a peak detector 52a for detecting the peak value of
the peak and a hold circuit 52b for holding the peak value detected by the peak detector 52a; 53
is a transmitter 1b according to the output from the peak hold circuit 52; It is a gain controller
that controls the gain of
A band-pass amplifier 51 having a characteristic as shown in FIG. 6 for extracting a characteristic
frequency region of speech is used as a discrimination detector for the utterance section and the
non-utterance section of the important problem (1).
As a pass band of this band-pass amplifier 51, one having 0.2 to 1 KHz or 0.2 to 2 KHz is used.
The reason is that most of human speech is speech, and most of the time and energy of speech is
vowels. Vowels (Japanese) are synthesized sounds of specific frequency spectrums called first,
second and third formants as shown in FIG. 7. Among them, most of the energy is occupied by
the first and second formants.
The first formants are distributed at about 0.2 to 1 KHz, and the second formants are distributed
at about 0.75 to 2 KHz. Therefore, setting the pass band of the band amplifier 51 to 0.2 to 2 KHz
enables selective extraction of the first and second formants of vowels, and setting the pass band
to 0.2 to 1 KHz selectively selects the first formant having the largest energy. Can be extracted.
Ambient noise includes many low frequency components (50 to 150 Hz) such as car and train
rotational noise and high frequency components (2 KHz or more) such as friction noise, and the
passband of the band amplifier is 0.2 to Setting at 2 KHz or 0.2 to 1 KHz is very effective for
identifying and extracting speech sounds of speech.
Next, the magnitude of the peak hold value of the output of the band amplifier 51 is used as
variable transmission gain control means for controlling so that the change in the gain in the
voiced section and the non-voiced section in the important problem (2) does not cause auditory
sense of discomfort. Continuous and smooth control can be realized by using a gain controller
that performs gain control according to.
As the gain controller 53, an analog multiplication circuit that outputs the multiplication result of
the gain control signal and the AC output from the transmitter 1b is suitable.
For example, as shown in FIG. 8, V0 = K (X1 -X2) (Y1 -Y2) = K.VI.VC.
Here, VI is a transmitter AC output, VC is a gain control signal, V0 is a control output, K is a
proportional constant, and gain G = K.VC.
Since VC is the magnitude of the peak hold value = amplitude value, the relationship between the
amplitude value and the output of the gain controller is proportional as shown in FIG. Note that,
instead of the analog multiplier, an FET multiplier (which utilizes a change in channel resistance
of the FET) or the like can also be used.
Next, the holding time of the utterance section should be taken into consideration of the holding
time of the vowel that occupies most of the speech, considering that the lower limit of the
spectrum of the first formant of the vowel is about 200 Hz, the longest cycle Tm of the vowel is
about Since it is considered to be 5 msec, the peak hold circuit 52 may set the holding time Th so
as to hold the peak value of the 5 msec periodic waveform for a predetermined time.
As described above, when the gain control circuit 53 is controlled by the output of the peak hold
circuit 52 in which the holding time Th is set (see FIG. 9), the gain during conversation becomes
substantially constant in proportion to the size of the speaker's voice. Therefore, there is no
interruption of voice on the way.
In addition, since the rise of the peak hold circuit 52 is very fast, high gain operation, that is,
sufficient volume can be transmitted from the beginning of conversation.
If the attenuation of the peak hold circuit 52 of this embodiment is examined at a time Tf to a
99% attenuation which may be considered to be outside the hold range practically, Tf = 13Th.
From the above-mentioned relational expression, this time Tf is 1 second or less, and the
attenuation is short enough for practical conversation. Therefore, when the speech
communication is completed, the peak hold circuit 52 attenuates within a sufficiently short time
following the peak value of the silent period operation, so ambient noise can be suppressed
When the holding time in the peak hold circuit 52 is defined as the time when the attenuation
rate from the peak value is within 30%, the holding time is 5 to 65 msec when the peak detector
52a is a one-way detection type. In the case of two-way detection type, by setting 2.5 to 32.5
msec, it is possible to prevent unnatural interruption of transmission by keeping the holding time
too short, and even when transmission is ended due to being too long, transmission is performed
for a long time It is possible to prevent the ambient noise suppression effect from becoming thin
while the speech output is large.
That is, if the holding time is set to 1 to 13 times the time period 5 msec corresponding to the
lowest frequency 200 Hz of the first formant of the vowel which is the largest component of the
transmission energy, the transmission ends without losing the smoothness. The later gain can be
reduced quickly to provide optimum control in practice.
In the two-way detection type, peak detection is performed in a half cycle as compared with the
one-way detection type, so that 1 to 13 times 2.5 msec is the optimum holding time.
According to the present invention, as described above, since listening to the stereo and
switching of the telephone call are instantaneously performed by switching the switch means,
multimedia such as a personal computer having a telephone function and a CD player can be
obtained. In the terminal, as a multi-functional voice terminal such as telephone call and stereo
listening, it is not necessary to exchange the handset of the hands free handset and the handset
for stereo every time the function is switched.
Furthermore, when making a call by telephone, the receiver integrated with the transmitter is
shut off, and a two-way communication is performed between the other receiver and the
transmitter. There is no voice wrap around the device, and howling can be prevented, so that
clear calls can be made.
Furthermore, since the transmitting / receiving circuit for the telephone has an ambient noise
control circuit for facilitating the call to suppress the ambient noise with respect to the telephone
signal, it is possible to make a clear call in a state where the ambient noise is high. It has the
effect of being able to improve the clarity of the telephone call.
Brief description of the drawings
1 is a block circuit diagram showing an embodiment of the present invention.
2 is a cross-sectional view of the earphone with a transmitter used in the embodiment of the
present invention.
3 is an overall configuration diagram of the earphone type.
4 is a configuration diagram of the entire headphone type.
5 is a block circuit diagram of the transmission and reception circuit.
6 is a frequency characteristic diagram of the band amplifier.
7 is a frequency characteristic diagram showing the formant of the Japanese vowel (generation).
8 is a gain controller by an analog multiplier.
9 is a gain characteristic diagram of the gain controller with respect to the amplitude value of the
microphone output.
Explanation of sign
Reference Signs List 1 handset 1a receiver 1b transmitter 2 receiver 3 telephone line 4 personal
computer 4a stereo unit 4b transmission / reception circuit 4c switch means (relay) 4d reception
detection circuit 5 ambient noise suppression circuit 51 band amplifier 52 peak hold circuit 53
gain controller
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