CA2094667A1 - Two-way communications earset with filter - Google Patents
Two-way communications earset with filterInfo
- Publication number
- CA2094667A1 CA2094667A1 CA002094667A CA2094667A CA2094667A1 CA 2094667 A1 CA2094667 A1 CA 2094667A1 CA 002094667 A CA002094667 A CA 002094667A CA 2094667 A CA2094667 A CA 2094667A CA 2094667 A1 CA2094667 A1 CA 2094667A1
- Authority
- CA
- Canada
- Prior art keywords
- filter
- microphone
- high end
- frequency
- ear
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R3/00—Circuits for transducers, loudspeakers or microphones
- H04R3/02—Circuits for transducers, loudspeakers or microphones for preventing acoustic reaction, i.e. acoustic oscillatory feedback
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R1/00—Details of transducers, loudspeakers or microphones
- H04R1/10—Earpieces; Attachments therefor ; Earphones; Monophonic headphones
- H04R1/1016—Earpieces of the intra-aural type
Landscapes
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Acoustics & Sound (AREA)
- Signal Processing (AREA)
- Health & Medical Sciences (AREA)
- General Health & Medical Sciences (AREA)
- Otolaryngology (AREA)
- Circuit For Audible Band Transducer (AREA)
- Headphones And Earphones (AREA)
- Details Of Audible-Bandwidth Transducers (AREA)
- Telephone Set Structure (AREA)
Abstract
ABSTRACT
A two way voice communications earset which is situated in the ear of the user and which includes a filter in an audio signal loop coupling a microphone and a speaker of the earset.
A two way voice communications earset which is situated in the ear of the user and which includes a filter in an audio signal loop coupling a microphone and a speaker of the earset.
Description
- \
2~94~7 BAcRGRouND OF THE INYI~GI~
The present invention relate~ generally to a two-way communications earset with a filter which i~ worn in or at the ear of the user for use in two-way voice communication~ and which i~
operated hands-free. The earset can transmit the user's voice and receive the voice signals of another party simultaneously without cau~ing feedback.
Modern wireless technolog~es have advanced to the extent that portable, wirele~ and mobile telephones have become ~mall in size and are used widely. Such portable telephones typically include a handset requiring the use of at lea~t one hand for communication.
A di~advantage of the handset type of telephone i~ that they are inconvenient to use in front of 8 computer or while driving a ; ~ -car. In ~uch in~tances, the n~er must u~e ~ hand to hold the handset while typing at the keyboard, which i~ very difficult to do, or whlle holding the ~teering wheel o~ a car, which is dangerous. Altern~tively, the user must hold the telephone handset to their ear wlth their ~houlder, which is very uncomfortable.
In order to solve this drawback, hands-free telephone~ have been developed. A conventional two-way communicationq apparatus used with hands-~ree telephones comprises a headband including a spe~er po~ltioned ln front of one ear ~nd a boom at~ached tO the headbsnd with a small microphone at one end of the boom. With the -boom connected to the headband, the microphone extends in front of the mouth of the user. However, this type of hands-free telephone 2094667 ~:
is not convenient to use because it is cumbersome and because it disturbs the hair of the user.
Another conventional two-way communications system used with hands-free telephones includes a structure which hangs from the ear of the user. This type of communications system include~ a speaker positioned in front of the user~s ear and a boom h~ving a microphone extending in front of the mouth of the user. Aga$n, such a structure i~ not convenient for the user because it ~-~
typically does not h~ng well at the ear and because it 18 bulky to carry owing to the boom.
15Yet another conventional two-way communication system comprises a ~peaker and a microphone both housed in an earset unit which is worn in the ear of the user. Such an ear~et does not require use of hands to operate and does not have a boom extending ~ - -in front of the user's mouth. However, a drawback of this earset 18 that users cannot increase the sound volumes of elther the speaker or the mlcrophone. Therefore, the use of thls type of ear~et is limited to quiet environments.
In addition, microphone sensitivity in such conventional earset~ i8 set to a low level. As a result, the user 18 difficult to hear. Also, because the sensitivity of the speaker i~ set at a low level a~ well, the user tend~ to cover the earset with a hand in order to obtaln improved communications in a noisy environment.
However, thls tends to cause feedback. ~ecause of these drawbacks, conventional ear~ets include a warning regarding the tendency for feedback and are not widely used.
209~7 S Accordingly, an object of the present invention is to provide an earset for use in two-way voice communication~ which i8 worn in ---or at the ear of the user and which is operated hands-free.
Another ob~ect of the present invention i8 to provide an earset which transmits the user~ 8 voice and receive~ voice signals from another party simultaneously without feedback caused by acoustic or mechanical coupling between the ~peaker and the microphone.
A further ob~ect of the present invention i~ to provlde an ear~et which delivers an adequate level of sound to the user without causing feedback, while also delivering an ndequate level of sound to a receiver at the other end of the communication ~ -system.
A still further ob~ect of the present invention is to provide an earset which includes a mechanical or electrical filter that eliminate~ audio frequencies tending to cause feedback.
Additional ob~ects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The ob~ects and advantages of the invention may be realized and obtained by means of the instrumentalitiea and combinations particularly pointed out in the appended claim~
SUMMARY OF TR~ _INV~NTION
To achieve the ob~ects in accordance with the purposes of the 30 pre~ent invention, as embodied and described herein, the earset of ~; -the present invention comprises a two-way simultaneous voice :`
20946~7 tran~mitting and receiving device comprising a case comprising an enlarged portion adapted to be placed in an ear auricle of a user and a hollow portion extending along a direction parallel to a mouth of the user, whersin the enlarged portion houses a speaker with an output led to an ear canal of the user and the hollow portion houses a mlcrophone, and means, sltuated within an audio signal loop coupling the speaker to the microphone, for filtering a high end range of audio frequencies that causes feedback.
The present inventlon further comprlses a two-way ~:.
slmultaneous volce transmittlnq and recelvlng device comprising a lS case including an enlarged portlon adapted to be placed in an aurlcle of a user's ea~ and a hollow portlon extending parallel to a mouth of the user, wherein the hollaw portion hou~es a microphone, and the enlarged portion houses a ~peaker wlth an output to an ear canal of the user, whereln the speaker passes frequencles ln a range of 300 to 1000 Hz and has a hlgh end cut off frequency below 2.5 XHz.
Alternatively, the present lnvention comprises a two-way ~ :
simultaneous voice transmittlng and recelvlng device comprising a case lncluding an enlarged portlon adapted to be placed in an aurlcle of a user's ear and a hollow portlon extending parallel to a mouth o~ the user, whereln the enlarged portlon houses a speaker wlth an output led lnto an ear can~l of the user, and the hollow portlon hou~es a mlcrophone, and whereln the mlcrophone passes frequencies in a range of 300 to 1000 Hz and has a high end cut off frequency below 2.5 KHz.
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209~6~7 BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and con~titute a part of the specification, illustrate the presently preferred apparatus of the present invention ~nd, together with the general description given above and the detailed de~cription of the preferred embodiments given below serve to explain the principles of the invention. In the drawingss `~`
Fig. 1 is a side view of an earset according to a f$rst `
embodiment of the pre~ent invention inserted in the ear of a user; ~ ~
Fig. 2 is sectional view of the first embodiment; ~-lS Fig. 3 is a side view of an earset according to a second embodiment of the present invention inserted in the ear of a user; ~ ~ -Fig. 4 is a sectional view of a mechanical filter used in the earset according to the present invention;
Fig. 5A i8 a circuit dlagram of low pass electrical filter 20 used in the earset according to the present invention; ;
Fig. 5B is a graphical representation of the frequency characteristlcs of the low pass electrical filter shown in ~;
Fig. SA;
Fig. 6A is a circuit diagram of a band pass electrical filter used in the earset according to the present invention;
Fig. 6B is a graphical representation of the frequency characterlstlcs of the band pass electrical filter shown in ~ -Fig. 6A;
Fig. 7 is a graphical representation showing the definition ~;
. .
30 of the cut off frequency within the frequency band without ripple. ;
,.~
35 ~5~ ~
..... , . , . ., . , , .. , .. . " , . . . . . . .... . . .. . .
20~ 7 Fig. 8 is a graphical representation showing the definition of the cut off frequency within the frequency band with ripple.
Fig. 9A is a block diagram of a frequency compensating filter; and Fig. 9B ls a graphical representation of the frequency characterist~cs of the compensatlng electrical filter shown in Fig. 9A.
:
DETAILED DESCRIPTION OF THE PREF~M ED EMBODIMENTS
A first embodiment of the earset accordlng to the present invention is described with reference to Figs. 1 and 2. AB shown in Fig~. 1 and 2, the ear~et 1 has an L-shaped configuratlon and is preferably made of plastic. The short arm of the ~-shaped earset 1 includes an enlarged portion la which is inserted in the ear canal of the user. The enlarged portion 1~ includes an earset component portion lb and an insertion portion lc.
The enlarged portion la is placed in the ear auricle of the user and the insertion portion lc is inserted lnto the ear canal.
The insertion portion lc is preferably shaped 80 that the ear canal of the user will not be completely clogged by the device and so that the devlce will not be 80 loose that feedback due to leaked ~ound is caused.
A speaker 3 is housed in the earset component portion lb and is supported by resllient material 4. The output of the speaker 3 i~ input to the insertion part lc and is fed into the ear canal of the user. The speaker 3 can preferably be elther a magnetic-type speaker or dynamic-type speaker. As shown in Figs. 1 ~nd 2, the 2~945~7 , . -5 speaker 3 is situated in the earset component portion lb. -~
However, in accordance with the present invention, the speaker 3 can be placed in an alternate location, so long as the output from ;
the speaker 3 is guided into the ear canal of the user.
The long arm of the L-shaped earset 1 preferably includes a hollow portion ld which has a small hole le at the lower end thereof and an electret type microphone 5 at an upper portion thereof. In accordance with the present invention, the microphone 5 can be either a bidirectional-type or a unidirectional-type microphone. A sound pipe 2 iB also contained within the hollow portion ld and connects the small hole le and the microphone 5.
In operation, the microphone 5 detects the voice signals of the user through the small hole le ~nd the sound pipe 2.
In the embodiment shown in Figs. 1 and 2, a filter 6 is placed within the sound pipe 2 and is situated between the m$crophone 5 and the small hole le. The fllter 6 passes audio frequencies withln a preferred range of 300 to 1000 Hz with a cut off frequency of preferably below 2.5 KHz, as described ln greater , " :
detail below. Additionally, as also described ln more detail below, the filter 6 c~n be located at alternate loc~tions in the earset. A wire 7 extends through the hollow portion ld and combines the wires from the speaker 3 and the microphone 5.
The e~rset 1 is operated in the following manner. When the earset 1 is situated ln the ear of the user, electrlcal sign~ls which are received are fed vla the wire 7 to the speaker 3. The speaker 3 emits sound to the ear canal of the user via a hole lf in the insertion portlon lc.
,~. .'~' , ,-, ~
20946~7 The voice signal of the person using the ear~et 1 pas~es ~ -through the small hole le and filter 6 and reaches the microphone 5. The microphone 5 converts the sound to electrical signals that are sent via the wire 7 to an amplifier, which is not shown ln Flgs. i or 2.
Fig. 3 shows a second embodiment of an earset accordlng to the present invention. As shown in Flg. 3, the device has a two- -piece construction including a two-way wireless communication device 8 connected to an earset 1. The communication device 8 includes a transmitter/recelver at the front portion of the ear ~, -lobe. The communication device also includes a battery cell located st the back portion of the ear lobe. The battery cell and the transmitter/receiver remain connected to the ear lobe by ~
pinching mechanism located therebetween. The earset 1, shown in Flg. 3, 18 substantially the s~me a8 that shown in Fig~. 1 and 2.
In order to design the eArset 1 of the present invention 80 that it most efficiently conducts two-way voice communications, the unique sound field around the auricle of the ear wns studied by the inventors of the present lnvention. This sound field was found to extend not only in front of the auricle, but al80 in the area surrounding the auricle and to result from a comblnation of the sound near the aurlcle, the ear canal and the head. It was al80 determ~ned that the sound field generates sound reflection, diffraction and resonance.
As a result of the inventors~ study of the sound field, acoustlc and mechanical coupllng between the speaker 3 and the microphone 5 wa~ determlned to increase selectively at a few 2~94667 :
S specific frequencies between 1 XHz and 3.4 XHz. The~e specific -frequencies vary depending on the type of earset worn by the user and the voice characteristics of the user.
It was also observed that when the sound volume of the speaker 3 i8 increa~ed and when the sensitivity of microphone 5 i8 increased, feedback tends to occur at the identified spec$fic frequencies. In addition, when the ear~et l is used under heavy ambient noise, the user tends to cover the ear containing the earset 1 with his hand in order to block out the ambient noi~e. ~-However, such hand placement acts as an ear muff and presents the ~ ~;
optimal condition for feedback to occur at these specific frequencies. Feedback between the speaker 3 and the microphone 5 also occurs when 8 portion of the voice output of speaker 3 is leaked. This leaked portion is reflected off the auricle structure of the ear and lnput to the microphone 5 via the small 20 hole le. -In order to reduce the deleterious a'ffects of acoustic coupling and feedback described above, 8ignals within the area of the specific frequencies are reduced. Although it is well known that reducing signals wlthin a certain frequency range can damage the quality of voice communications, according to the pre~ent Lnvention, the speciflc identified frequencies can be reduced without lowering the quality of voice communications.
Additionally, acoustic coupling and feedback can also be signlficantly reduced. --~
30Specifically with respecl: to reducing the identified frequencles, the inventors of the present lnvention found that if _ g _ --, .. , . , .. , . . . . ~ .. . ~ .. . . . ...... ..
.~:. . ~.; ,........... , . , . . . , j, . .
. :~. : .. :. , :
. ., ~ . , ; ~
2094~67 ~
the high end cut off frequency was made too low, the quality of voice communicatlons would be unacceptable. Conversely, if the - ;-high end cut off frequency was set too high, feedback occurred too readily. The lnventors also considered that when sound passes from a free sound f$eld to the ear drum, the sound pressure of 10 6ignals between 1 KHz to around 2.5 RHz incresses. ~ ;-By balancing the effect~ of acoustlc snd mechanical coupling, the likelihood of feedback, and sound pressure with sn acceptable level of voice communication, according to the present invention, the filter 6 preferably is conflgured to pass frequencies in the range of 300 to 1000 Hz and to preferably have a high end cut off frequency of below 2.5 RHz.
Additionally, the filter 6 is situated in the ear~et 1 in an audio signal loop coupling the speaker 3 and the microphone 5.
The audio signal loop is defined as electrical or mechanical connection between the speaker 3 and the microphone 5. By placing the filter anywhere within the audio signal loop, feedback between the speaker 3 and microphone 5 can be substantlally reduced.
Several different placements of the filter 6 are contemplated. For example, with the fllter 6 coupled to the speaker 3, the speaker 3 will preferably have output characterlstics that pass low frequencies in the range of 300 Hz to 1,000 Hz and have a high end cut-off frequency of below 2.5 KHz. Alternatively, with the filter 6 coupled to the microphone 5, electrical signals from the microphone 5 will preferably have signal ch~racteristLcs that pass low frequencies in the range of 300 Hz to 1,000 Hz and have a hlgh end cut-off . :., -~ 209 4~7 .:
5 frequency of below 2.5 XHz. And alternatively, two or more -filters with portions of the desired frequency response can be -;
allocated between the qpeaker 3 and microphone 5 in the audio signal loop.
....~ ....~
In addition to reducing acoustic coupling and feedback and .. ~.. ~ - .
producing an acceptable voice signal, it is desirable that the earset 1 in of the present invention be ~ensltlve to human voice signalq, but not to ambient noise or nolse that 1~ leaked from the speaker 3. Because the earset 1 lq ~mall in size and is mounted ~ -at the entrance of the ear canal of the user, it iq preferable t~at the earset 1 have a structure which provldes a greater . ~ ,.
sensitivity to voice signals and a lesser ~ensltivity to sound --~-,, -, , reaching the earset 1 from other dlrections.
To achleve this result, mechanical fllter 61 i~ u~ed to , .
improve the directional sensitivity of the earset 1. Fig. 4 is a ~lde vlew of a mechanlcal fllter 61 which may be employed ln the earset 1 shown in Figs. 1-3. A~ shown in Fig. 4, the filter 61 is preferably made of a fiber sheet coiled 80 that the sheet flts into the cylindrically ehaped hollow portion ld.
Preferably, the filter 61 comprises a coil of highly fibrous ~ ;
25 paper tightly wound and filling the hollow portion ld, which ~
~: ., preferably has a diameter of 6 mm. The mechanical filter 61 is constructed 80 that lt has the frequency characteristic~ described above. ~he resultant frequency characterlstic can be varied by changing the density of the coil, ie., reducing the number of co~l-q.
: ' .. ....
,., ,~ ,,,, ~
2094~7 With such a colled ~tructure, sound coming from a direction parallel to the axis of the mechanical filter 61 passes through to microphone 5 with less attenuation than sound coming from other directions. Becau~e voice signals coming from the user primarily emanate along an axis parallel to the axis of the mechanical filter 61, the~e signals are less attenuated than those of other signal~ reaching ~he microphone 5 and the sensitivity to voice signals is therefore improved.
In the embodiment of the mechanicsl filter 6 shown in Fig. 3, the ~tructure of the coiled fiber sheet achieves the desired frequency response and improves the sensitivity of the earset 1 to voice ~ignal~. Alternatively, the mechanical filter 61 may be constructed of glass wool, rock wool, felt, materials such as high density sponge, or fibres made of cotton and pulp. More specifically, the mechanlcal filter 61 may comprise a cigarette filter, compri~ing cotton fiber~, because it has been found that cigarette filters can achieve the desired frequency characteristics. Additionally, a cigarette filter fits withln the hollow portlon ld and are readily available.
It should al~o be noted that Figs. 1 and 2 ~how an embodiment ln which a mechanlcal filter 6 is positioned in front of microphone 5. However, as discus~ed above, a mechanical filter 6 with a simllar frequency response can alternativsly be placed in front of the speaker 3. It i8 al~o contemplated that a fir~t mechanical filter 6 with a portion of the desired filter characteristics be placed in front of the microphone 5 while ~ r;
another mechanical filte~ 6, having another portion of the desired frequency response, be positioned in front of the speaker 3.
Alternatively, the filter 6 may preferably comprise ~-electrlcal component~, as shown in Figs. SA and 6A. Fig. 5A shows a low pa~ filter 62 comprising an operational amplifier 9 which can be used 8~ the filter 6 of the earset 1. Fig. 6A show~ a band pass filter 63 also comprising an operation~l ~mplifier 10 which can be used as the filter 6 of the earset 1. Fig. 5~ and Fig. 6B ~-show the frequency responses of the filters shown in Fig. SA and ~;
Fig. 6A, respectively.
Preferably, the operational amplifier may comprise a National Semiconductor LM324 type operational ampl$fier although alternative devices are known or can be designed by those of ordlnary skill in the art. Additionally, as described with the mechanical filter 61, the low pass filter 62 and the band pass fllter 63 are preferably placed in the audio loop between the speaker 3 snd the microphone 5.
As descrlbed above, accordlng to the present lnventlon, the high end cut off frequency of the filter 6 is preferably below 2.5 RHz. When one of the low pass fllter 62 or the band pass fllter 63 are used as the fllter 6 of the earset 1, a determination of the high end cut off frequency is made depending on the char~cteristics of the filter 6. That i8 ~ the high end cut off frequencies for a frequency band with or wlthout amplitude ripple, as shown ln Fig. 7 ~nd Flg. 8, respectlvely, will be dlfferent.
-13- ~
-~ -:
, s : : :, ~
20~46~7 - ~
S More specifically, in accordance with the present invention, the high end cut off frequency of the low pass or band pass filter~ 62 and 63 i~hown, respectively, in Fig~. SA and 6A is defined such that if the filter 6 does not ha~e a ripple characteristic within the frequency range allowed to pass therethrough, as ~hown in Fig. 7, the cut-off freguency of the filter 6 is defined as that after which an output from the filter 6 becomes 3 dB below the maximum amplitude within the sllowsble frequency range. Alternat$vely, if the filter 6 does have a ripple characterlstic with$n the frequency range allowed to pass lS therethrough, as shown in Fig. 8, tha cut-off frequency is defined as that frequency after which an output from the filter 6 becomes 3 dB below the average amplitude within the allowed frequency range.
However, constructed as shown in Flgs. 5A and 6A, the filters 62 and 63, may cut off certain high frequency components of the speech signals and may therefore deteriorate voice communications. In order to make up for this, an alternative filter 64 which includes a compen~ating circuit can be used.
Fig. 9A i8 a circuit dlagram of such a compensation filter 64. The compensnting filter 64 shown in Fig. 9A, improYes the 1089 of high frequencies which may be filtered out by filter~ 62 and 63, shown in Figs. SA and 6A. Fig. 9B is ~ graphical representation of the frequency response of the circuit shown in Fig. 9A.
More specifically, in operation, the microphone S of the earset 1, shown in Figs. 1-3, produces an electrical slgnal output : ~
- 2 0 9 4 ~ ~ 7 -:.
6a. Output 6a i~ fed into audio band limiting filter 6b which as ~hown in Fig. 9~ produces a band pass filter response similar to that ~hown in Fig. 6B. It i~ also contemplated that the output 6a can emanate from the ~peaker 3.
The output 6a is also input to high end audio select filter 10 6cl of the high end audio amplitude limiter 6c. The high end - -audio select filter 6cl passes selected high end audio ~;~
frequencie~. The frequency response of the high end audio select filter 6cl $8 shown in Flg. gB. The output of the hlgh end audio select filter 6cl is fed into amplitude limiter 6c2 which limit~
the output of the high end audio select filter to a predetermined level. The output of the amplitude limiter 6c2 is fed into attenuator 6d. The outputs of audio band limiting filter 6b and attenuator 6d are added by the adder 6e. ~ ;
A graphical representation of the frequency response of the filter 64, ~hown in Fig. 9A, is shown in F~g. 9~. The frequency response includes the both the 6b characteristlcs, the output from the audio band limiting filter, Mnd the 6cl characteristic~, the output from the attenuator 6d. Accordlngly, with the filter 64 of the present invention, the amplitude~ of high frequencies are controlled below a certain level b~ amplitude limiter 6c2 ~o that feedback wlll not occur. In addition, because some high frequencie~ are left ln the resultant output signal, ~8 a result of the addition of high end signal~ to those of the audio band limiting filter 6b, the resultant voice signal will not be deteriorated.
, ~ :
-15- ~ ~
- ~ . , 1 2~9~67 Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims.
The present invention relate~ generally to a two-way communications earset with a filter which i~ worn in or at the ear of the user for use in two-way voice communication~ and which i~
operated hands-free. The earset can transmit the user's voice and receive the voice signals of another party simultaneously without cau~ing feedback.
Modern wireless technolog~es have advanced to the extent that portable, wirele~ and mobile telephones have become ~mall in size and are used widely. Such portable telephones typically include a handset requiring the use of at lea~t one hand for communication.
A di~advantage of the handset type of telephone i~ that they are inconvenient to use in front of 8 computer or while driving a ; ~ -car. In ~uch in~tances, the n~er must u~e ~ hand to hold the handset while typing at the keyboard, which i~ very difficult to do, or whlle holding the ~teering wheel o~ a car, which is dangerous. Altern~tively, the user must hold the telephone handset to their ear wlth their ~houlder, which is very uncomfortable.
In order to solve this drawback, hands-free telephone~ have been developed. A conventional two-way communicationq apparatus used with hands-~ree telephones comprises a headband including a spe~er po~ltioned ln front of one ear ~nd a boom at~ached tO the headbsnd with a small microphone at one end of the boom. With the -boom connected to the headband, the microphone extends in front of the mouth of the user. However, this type of hands-free telephone 2094667 ~:
is not convenient to use because it is cumbersome and because it disturbs the hair of the user.
Another conventional two-way communications system used with hands-free telephones includes a structure which hangs from the ear of the user. This type of communications system include~ a speaker positioned in front of the user~s ear and a boom h~ving a microphone extending in front of the mouth of the user. Aga$n, such a structure i~ not convenient for the user because it ~-~
typically does not h~ng well at the ear and because it 18 bulky to carry owing to the boom.
15Yet another conventional two-way communication system comprises a ~peaker and a microphone both housed in an earset unit which is worn in the ear of the user. Such an ear~et does not require use of hands to operate and does not have a boom extending ~ - -in front of the user's mouth. However, a drawback of this earset 18 that users cannot increase the sound volumes of elther the speaker or the mlcrophone. Therefore, the use of thls type of ear~et is limited to quiet environments.
In addition, microphone sensitivity in such conventional earset~ i8 set to a low level. As a result, the user 18 difficult to hear. Also, because the sensitivity of the speaker i~ set at a low level a~ well, the user tend~ to cover the earset with a hand in order to obtaln improved communications in a noisy environment.
However, thls tends to cause feedback. ~ecause of these drawbacks, conventional ear~ets include a warning regarding the tendency for feedback and are not widely used.
209~7 S Accordingly, an object of the present invention is to provide an earset for use in two-way voice communication~ which i8 worn in ---or at the ear of the user and which is operated hands-free.
Another ob~ect of the present invention i8 to provide an earset which transmits the user~ 8 voice and receive~ voice signals from another party simultaneously without feedback caused by acoustic or mechanical coupling between the ~peaker and the microphone.
A further ob~ect of the present invention i~ to provlde an ear~et which delivers an adequate level of sound to the user without causing feedback, while also delivering an ndequate level of sound to a receiver at the other end of the communication ~ -system.
A still further ob~ect of the present invention is to provide an earset which includes a mechanical or electrical filter that eliminate~ audio frequencies tending to cause feedback.
Additional ob~ects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The ob~ects and advantages of the invention may be realized and obtained by means of the instrumentalitiea and combinations particularly pointed out in the appended claim~
SUMMARY OF TR~ _INV~NTION
To achieve the ob~ects in accordance with the purposes of the 30 pre~ent invention, as embodied and described herein, the earset of ~; -the present invention comprises a two-way simultaneous voice :`
20946~7 tran~mitting and receiving device comprising a case comprising an enlarged portion adapted to be placed in an ear auricle of a user and a hollow portion extending along a direction parallel to a mouth of the user, whersin the enlarged portion houses a speaker with an output led to an ear canal of the user and the hollow portion houses a mlcrophone, and means, sltuated within an audio signal loop coupling the speaker to the microphone, for filtering a high end range of audio frequencies that causes feedback.
The present inventlon further comprlses a two-way ~:.
slmultaneous volce transmittlnq and recelvlng device comprising a lS case including an enlarged portlon adapted to be placed in an aurlcle of a user's ea~ and a hollow portlon extending parallel to a mouth of the user, wherein the hollaw portion hou~es a microphone, and the enlarged portion houses a ~peaker wlth an output to an ear canal of the user, whereln the speaker passes frequencles ln a range of 300 to 1000 Hz and has a hlgh end cut off frequency below 2.5 XHz.
Alternatively, the present lnvention comprises a two-way ~ :
simultaneous voice transmittlng and recelvlng device comprising a case lncluding an enlarged portlon adapted to be placed in an aurlcle of a user's ear and a hollow portlon extending parallel to a mouth o~ the user, whereln the enlarged portlon houses a speaker wlth an output led lnto an ear can~l of the user, and the hollow portlon hou~es a mlcrophone, and whereln the mlcrophone passes frequencies in a range of 300 to 1000 Hz and has a high end cut off frequency below 2.5 KHz.
",,','.. s-, , ,~ " ~ , " ~ ;"", ~ :.
209~6~7 BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and con~titute a part of the specification, illustrate the presently preferred apparatus of the present invention ~nd, together with the general description given above and the detailed de~cription of the preferred embodiments given below serve to explain the principles of the invention. In the drawingss `~`
Fig. 1 is a side view of an earset according to a f$rst `
embodiment of the pre~ent invention inserted in the ear of a user; ~ ~
Fig. 2 is sectional view of the first embodiment; ~-lS Fig. 3 is a side view of an earset according to a second embodiment of the present invention inserted in the ear of a user; ~ ~ -Fig. 4 is a sectional view of a mechanical filter used in the earset according to the present invention;
Fig. 5A i8 a circuit dlagram of low pass electrical filter 20 used in the earset according to the present invention; ;
Fig. 5B is a graphical representation of the frequency characteristlcs of the low pass electrical filter shown in ~;
Fig. SA;
Fig. 6A is a circuit diagram of a band pass electrical filter used in the earset according to the present invention;
Fig. 6B is a graphical representation of the frequency characterlstlcs of the band pass electrical filter shown in ~ -Fig. 6A;
Fig. 7 is a graphical representation showing the definition ~;
. .
30 of the cut off frequency within the frequency band without ripple. ;
,.~
35 ~5~ ~
..... , . , . ., . , , .. , .. . " , . . . . . . .... . . .. . .
20~ 7 Fig. 8 is a graphical representation showing the definition of the cut off frequency within the frequency band with ripple.
Fig. 9A is a block diagram of a frequency compensating filter; and Fig. 9B ls a graphical representation of the frequency characterist~cs of the compensatlng electrical filter shown in Fig. 9A.
:
DETAILED DESCRIPTION OF THE PREF~M ED EMBODIMENTS
A first embodiment of the earset accordlng to the present invention is described with reference to Figs. 1 and 2. AB shown in Fig~. 1 and 2, the ear~et 1 has an L-shaped configuratlon and is preferably made of plastic. The short arm of the ~-shaped earset 1 includes an enlarged portion la which is inserted in the ear canal of the user. The enlarged portion 1~ includes an earset component portion lb and an insertion portion lc.
The enlarged portion la is placed in the ear auricle of the user and the insertion portion lc is inserted lnto the ear canal.
The insertion portion lc is preferably shaped 80 that the ear canal of the user will not be completely clogged by the device and so that the devlce will not be 80 loose that feedback due to leaked ~ound is caused.
A speaker 3 is housed in the earset component portion lb and is supported by resllient material 4. The output of the speaker 3 i~ input to the insertion part lc and is fed into the ear canal of the user. The speaker 3 can preferably be elther a magnetic-type speaker or dynamic-type speaker. As shown in Figs. 1 ~nd 2, the 2~945~7 , . -5 speaker 3 is situated in the earset component portion lb. -~
However, in accordance with the present invention, the speaker 3 can be placed in an alternate location, so long as the output from ;
the speaker 3 is guided into the ear canal of the user.
The long arm of the L-shaped earset 1 preferably includes a hollow portion ld which has a small hole le at the lower end thereof and an electret type microphone 5 at an upper portion thereof. In accordance with the present invention, the microphone 5 can be either a bidirectional-type or a unidirectional-type microphone. A sound pipe 2 iB also contained within the hollow portion ld and connects the small hole le and the microphone 5.
In operation, the microphone 5 detects the voice signals of the user through the small hole le ~nd the sound pipe 2.
In the embodiment shown in Figs. 1 and 2, a filter 6 is placed within the sound pipe 2 and is situated between the m$crophone 5 and the small hole le. The fllter 6 passes audio frequencies withln a preferred range of 300 to 1000 Hz with a cut off frequency of preferably below 2.5 KHz, as described ln greater , " :
detail below. Additionally, as also described ln more detail below, the filter 6 c~n be located at alternate loc~tions in the earset. A wire 7 extends through the hollow portion ld and combines the wires from the speaker 3 and the microphone 5.
The e~rset 1 is operated in the following manner. When the earset 1 is situated ln the ear of the user, electrlcal sign~ls which are received are fed vla the wire 7 to the speaker 3. The speaker 3 emits sound to the ear canal of the user via a hole lf in the insertion portlon lc.
,~. .'~' , ,-, ~
20946~7 The voice signal of the person using the ear~et 1 pas~es ~ -through the small hole le and filter 6 and reaches the microphone 5. The microphone 5 converts the sound to electrical signals that are sent via the wire 7 to an amplifier, which is not shown ln Flgs. i or 2.
Fig. 3 shows a second embodiment of an earset accordlng to the present invention. As shown in Flg. 3, the device has a two- -piece construction including a two-way wireless communication device 8 connected to an earset 1. The communication device 8 includes a transmitter/recelver at the front portion of the ear ~, -lobe. The communication device also includes a battery cell located st the back portion of the ear lobe. The battery cell and the transmitter/receiver remain connected to the ear lobe by ~
pinching mechanism located therebetween. The earset 1, shown in Flg. 3, 18 substantially the s~me a8 that shown in Fig~. 1 and 2.
In order to design the eArset 1 of the present invention 80 that it most efficiently conducts two-way voice communications, the unique sound field around the auricle of the ear wns studied by the inventors of the present lnvention. This sound field was found to extend not only in front of the auricle, but al80 in the area surrounding the auricle and to result from a comblnation of the sound near the aurlcle, the ear canal and the head. It was al80 determ~ned that the sound field generates sound reflection, diffraction and resonance.
As a result of the inventors~ study of the sound field, acoustlc and mechanical coupllng between the speaker 3 and the microphone 5 wa~ determlned to increase selectively at a few 2~94667 :
S specific frequencies between 1 XHz and 3.4 XHz. The~e specific -frequencies vary depending on the type of earset worn by the user and the voice characteristics of the user.
It was also observed that when the sound volume of the speaker 3 i8 increa~ed and when the sensitivity of microphone 5 i8 increased, feedback tends to occur at the identified spec$fic frequencies. In addition, when the ear~et l is used under heavy ambient noise, the user tends to cover the ear containing the earset 1 with his hand in order to block out the ambient noi~e. ~-However, such hand placement acts as an ear muff and presents the ~ ~;
optimal condition for feedback to occur at these specific frequencies. Feedback between the speaker 3 and the microphone 5 also occurs when 8 portion of the voice output of speaker 3 is leaked. This leaked portion is reflected off the auricle structure of the ear and lnput to the microphone 5 via the small 20 hole le. -In order to reduce the deleterious a'ffects of acoustic coupling and feedback described above, 8ignals within the area of the specific frequencies are reduced. Although it is well known that reducing signals wlthin a certain frequency range can damage the quality of voice communications, according to the pre~ent Lnvention, the speciflc identified frequencies can be reduced without lowering the quality of voice communications.
Additionally, acoustic coupling and feedback can also be signlficantly reduced. --~
30Specifically with respecl: to reducing the identified frequencles, the inventors of the present lnvention found that if _ g _ --, .. , . , .. , . . . . ~ .. . ~ .. . . . ...... ..
.~:. . ~.; ,........... , . , . . . , j, . .
. :~. : .. :. , :
. ., ~ . , ; ~
2094~67 ~
the high end cut off frequency was made too low, the quality of voice communicatlons would be unacceptable. Conversely, if the - ;-high end cut off frequency was set too high, feedback occurred too readily. The lnventors also considered that when sound passes from a free sound f$eld to the ear drum, the sound pressure of 10 6ignals between 1 KHz to around 2.5 RHz incresses. ~ ;-By balancing the effect~ of acoustlc snd mechanical coupling, the likelihood of feedback, and sound pressure with sn acceptable level of voice communication, according to the present invention, the filter 6 preferably is conflgured to pass frequencies in the range of 300 to 1000 Hz and to preferably have a high end cut off frequency of below 2.5 RHz.
Additionally, the filter 6 is situated in the ear~et 1 in an audio signal loop coupling the speaker 3 and the microphone 5.
The audio signal loop is defined as electrical or mechanical connection between the speaker 3 and the microphone 5. By placing the filter anywhere within the audio signal loop, feedback between the speaker 3 and microphone 5 can be substantlally reduced.
Several different placements of the filter 6 are contemplated. For example, with the fllter 6 coupled to the speaker 3, the speaker 3 will preferably have output characterlstics that pass low frequencies in the range of 300 Hz to 1,000 Hz and have a high end cut-off frequency of below 2.5 KHz. Alternatively, with the filter 6 coupled to the microphone 5, electrical signals from the microphone 5 will preferably have signal ch~racteristLcs that pass low frequencies in the range of 300 Hz to 1,000 Hz and have a hlgh end cut-off . :., -~ 209 4~7 .:
5 frequency of below 2.5 XHz. And alternatively, two or more -filters with portions of the desired frequency response can be -;
allocated between the qpeaker 3 and microphone 5 in the audio signal loop.
....~ ....~
In addition to reducing acoustic coupling and feedback and .. ~.. ~ - .
producing an acceptable voice signal, it is desirable that the earset 1 in of the present invention be ~ensltlve to human voice signalq, but not to ambient noise or nolse that 1~ leaked from the speaker 3. Because the earset 1 lq ~mall in size and is mounted ~ -at the entrance of the ear canal of the user, it iq preferable t~at the earset 1 have a structure which provldes a greater . ~ ,.
sensitivity to voice signals and a lesser ~ensltivity to sound --~-,, -, , reaching the earset 1 from other dlrections.
To achleve this result, mechanical fllter 61 i~ u~ed to , .
improve the directional sensitivity of the earset 1. Fig. 4 is a ~lde vlew of a mechanlcal fllter 61 which may be employed ln the earset 1 shown in Figs. 1-3. A~ shown in Fig. 4, the filter 61 is preferably made of a fiber sheet coiled 80 that the sheet flts into the cylindrically ehaped hollow portion ld.
Preferably, the filter 61 comprises a coil of highly fibrous ~ ;
25 paper tightly wound and filling the hollow portion ld, which ~
~: ., preferably has a diameter of 6 mm. The mechanical filter 61 is constructed 80 that lt has the frequency characteristic~ described above. ~he resultant frequency characterlstic can be varied by changing the density of the coil, ie., reducing the number of co~l-q.
: ' .. ....
,., ,~ ,,,, ~
2094~7 With such a colled ~tructure, sound coming from a direction parallel to the axis of the mechanical filter 61 passes through to microphone 5 with less attenuation than sound coming from other directions. Becau~e voice signals coming from the user primarily emanate along an axis parallel to the axis of the mechanical filter 61, the~e signals are less attenuated than those of other signal~ reaching ~he microphone 5 and the sensitivity to voice signals is therefore improved.
In the embodiment of the mechanicsl filter 6 shown in Fig. 3, the ~tructure of the coiled fiber sheet achieves the desired frequency response and improves the sensitivity of the earset 1 to voice ~ignal~. Alternatively, the mechanical filter 61 may be constructed of glass wool, rock wool, felt, materials such as high density sponge, or fibres made of cotton and pulp. More specifically, the mechanlcal filter 61 may comprise a cigarette filter, compri~ing cotton fiber~, because it has been found that cigarette filters can achieve the desired frequency characteristics. Additionally, a cigarette filter fits withln the hollow portlon ld and are readily available.
It should al~o be noted that Figs. 1 and 2 ~how an embodiment ln which a mechanlcal filter 6 is positioned in front of microphone 5. However, as discus~ed above, a mechanical filter 6 with a simllar frequency response can alternativsly be placed in front of the speaker 3. It i8 al~o contemplated that a fir~t mechanical filter 6 with a portion of the desired filter characteristics be placed in front of the microphone 5 while ~ r;
another mechanical filte~ 6, having another portion of the desired frequency response, be positioned in front of the speaker 3.
Alternatively, the filter 6 may preferably comprise ~-electrlcal component~, as shown in Figs. SA and 6A. Fig. 5A shows a low pa~ filter 62 comprising an operational amplifier 9 which can be used 8~ the filter 6 of the earset 1. Fig. 6A show~ a band pass filter 63 also comprising an operation~l ~mplifier 10 which can be used as the filter 6 of the earset 1. Fig. 5~ and Fig. 6B ~-show the frequency responses of the filters shown in Fig. SA and ~;
Fig. 6A, respectively.
Preferably, the operational amplifier may comprise a National Semiconductor LM324 type operational ampl$fier although alternative devices are known or can be designed by those of ordlnary skill in the art. Additionally, as described with the mechanical filter 61, the low pass filter 62 and the band pass fllter 63 are preferably placed in the audio loop between the speaker 3 snd the microphone 5.
As descrlbed above, accordlng to the present lnventlon, the high end cut off frequency of the filter 6 is preferably below 2.5 RHz. When one of the low pass fllter 62 or the band pass fllter 63 are used as the fllter 6 of the earset 1, a determination of the high end cut off frequency is made depending on the char~cteristics of the filter 6. That i8 ~ the high end cut off frequencies for a frequency band with or wlthout amplitude ripple, as shown ln Fig. 7 ~nd Flg. 8, respectlvely, will be dlfferent.
-13- ~
-~ -:
, s : : :, ~
20~46~7 - ~
S More specifically, in accordance with the present invention, the high end cut off frequency of the low pass or band pass filter~ 62 and 63 i~hown, respectively, in Fig~. SA and 6A is defined such that if the filter 6 does not ha~e a ripple characteristic within the frequency range allowed to pass therethrough, as ~hown in Fig. 7, the cut-off freguency of the filter 6 is defined as that after which an output from the filter 6 becomes 3 dB below the maximum amplitude within the sllowsble frequency range. Alternat$vely, if the filter 6 does have a ripple characterlstic with$n the frequency range allowed to pass lS therethrough, as shown in Fig. 8, tha cut-off frequency is defined as that frequency after which an output from the filter 6 becomes 3 dB below the average amplitude within the allowed frequency range.
However, constructed as shown in Flgs. 5A and 6A, the filters 62 and 63, may cut off certain high frequency components of the speech signals and may therefore deteriorate voice communications. In order to make up for this, an alternative filter 64 which includes a compen~ating circuit can be used.
Fig. 9A i8 a circuit dlagram of such a compensation filter 64. The compensnting filter 64 shown in Fig. 9A, improYes the 1089 of high frequencies which may be filtered out by filter~ 62 and 63, shown in Figs. SA and 6A. Fig. 9B is ~ graphical representation of the frequency response of the circuit shown in Fig. 9A.
More specifically, in operation, the microphone S of the earset 1, shown in Figs. 1-3, produces an electrical slgnal output : ~
- 2 0 9 4 ~ ~ 7 -:.
6a. Output 6a i~ fed into audio band limiting filter 6b which as ~hown in Fig. 9~ produces a band pass filter response similar to that ~hown in Fig. 6B. It i~ also contemplated that the output 6a can emanate from the ~peaker 3.
The output 6a is also input to high end audio select filter 10 6cl of the high end audio amplitude limiter 6c. The high end - -audio select filter 6cl passes selected high end audio ~;~
frequencie~. The frequency response of the high end audio select filter 6cl $8 shown in Flg. gB. The output of the hlgh end audio select filter 6cl is fed into amplitude limiter 6c2 which limit~
the output of the high end audio select filter to a predetermined level. The output of the amplitude limiter 6c2 is fed into attenuator 6d. The outputs of audio band limiting filter 6b and attenuator 6d are added by the adder 6e. ~ ;
A graphical representation of the frequency response of the filter 64, ~hown in Fig. 9A, is shown in F~g. 9~. The frequency response includes the both the 6b characteristlcs, the output from the audio band limiting filter, Mnd the 6cl characteristic~, the output from the attenuator 6d. Accordlngly, with the filter 64 of the present invention, the amplitude~ of high frequencies are controlled below a certain level b~ amplitude limiter 6c2 ~o that feedback wlll not occur. In addition, because some high frequencie~ are left ln the resultant output signal, ~8 a result of the addition of high end signal~ to those of the audio band limiting filter 6b, the resultant voice signal will not be deteriorated.
, ~ :
-15- ~ ~
- ~ . , 1 2~9~67 Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims.
Claims (9)
1. A two-way simultaneous voice transmitting and receiving device comprising:
a case comprising an enlarged portion adapted to be placed in an ear auricle of a user and a hollow portion extending in a direction away from the ear, wherein the enlarged portion houses a speaker with an output led to an ear canal of the user and the hollow portion houses a microphone; and means, situated within an audio signal loop coupling the speaker to the microphone, for filtering a high end range of audio frequencies that causes feedback.
a case comprising an enlarged portion adapted to be placed in an ear auricle of a user and a hollow portion extending in a direction away from the ear, wherein the enlarged portion houses a speaker with an output led to an ear canal of the user and the hollow portion houses a microphone; and means, situated within an audio signal loop coupling the speaker to the microphone, for filtering a high end range of audio frequencies that causes feedback.
2. The two-way simultaneous voice transmitting and receiving device according to claim 1, wherein the filter comprises one of a low pass filter and a band pass filter and passes audio frequencies in a range of 300 Hz to 1000 Hz and has a high end cut off frequency of below 2.5 KHz.
3. The two-way simultaneous voice transmitting and receiving device according to claim 2, wherein the high end cut off frequency is defined such that if the filter does not have a ripple characteristic within an allowable frequency range, the high end cut off frequency is a frequency after which the output of the filter is less than 3 dB below a maximum amplitude of the allowable frequency range, and if the filter has a ripple characteristic within the allowable frequency range, the high end cut off frequency is a frequency after which the output of the filter is less than 3 dB below an average amplitude of the allowable frequency range.
4. The two-way simultaneous voice transmitting and receiving device according to claim 1, wherein the filter means comprises sound absorbing material positioned in an area between a sound intake hole in the hollow portion and a diaphragm of the microphone.
5. The two-way simultaneous voice transmitting and receiving device according to claim 4, wherein the sound absorbing material is situated in the space between the sound intake hole and the diaphragm of the microphone and provides sound directivity to voice signals of the user.
6. The two-way simultaneous voice transmitting and receiving device according to claim 4, wherein the sound absorbing material comprises one of a coiled fiber sheet, glass wool, rock wool, felt, a high density sponge, cotton fibers and pulp fibers.
7. The two-way simultaneous voice transmitting and receiving device according to claim 2, wherein the filter means comprises:
a high end audio select filter, connected to the microphone, which passes high end audio frequencies and which outputs a first signal with an amplitude;
an amplitude limiter, coupled to the high end audio select filter, which limits the amplitude of the first signal output from the high end audio select filter below a predetermined level;
an audio band limiting filter, connected to the microphone, which bypasses the high end audio select filter and the amplitude limiter and outputs a second signal; and an adder, coupled to the audio band limiting filter and to the amplitude limiter, for adding the first and second signals.
a high end audio select filter, connected to the microphone, which passes high end audio frequencies and which outputs a first signal with an amplitude;
an amplitude limiter, coupled to the high end audio select filter, which limits the amplitude of the first signal output from the high end audio select filter below a predetermined level;
an audio band limiting filter, connected to the microphone, which bypasses the high end audio select filter and the amplitude limiter and outputs a second signal; and an adder, coupled to the audio band limiting filter and to the amplitude limiter, for adding the first and second signals.
8. A two-way simultaneous voice transmitting and receiving device comprising a case including an enlarged portion adapted to be placed in an auricle of a user's ear and a hollow portion extending away from the ear, wherein the hollow portion houses a microphone, and the enlarged portion houses a speaker with an output to an ear canal of the user, wherein the speaker passes frequencies in a range of 300 to 1000 Hz and has a high end cut off frequency below 2.5 KHz.
9. A two-way simultaneous voice transmitting and receiving device comprising a case including an enlarged portion adapted to be placed in an auricle of a user's ear and a hollow portion extending away from the ear, wherein the enlarged portion houses a speaker with an output led into an ear canal of the user, and the hollow portion houses a microphone, and wherein the microphone passes frequencies in a range of 300 to 1000 Hz and has a high end cut off frequency below 2.5 KHz.
Priority Applications (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4092457A JPH0817415B2 (en) | 1992-03-19 | 1992-03-19 | Earset type handset |
| EP93104560A EP0564874B1 (en) | 1992-03-19 | 1993-03-19 | Two-way communications earset with filter |
| ES93104560T ES2108151T3 (en) | 1992-03-19 | 1993-03-19 | TWO-WAY COMMUNICATIONS MICROPHONE WITH FILTER. |
| DE69313902T DE69313902T2 (en) | 1992-03-19 | 1993-03-19 | Two-way communication earphones with filter |
| CA002094667A CA2094667A1 (en) | 1992-03-19 | 1993-04-22 | Two-way communications earset with filter |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4092457A JPH0817415B2 (en) | 1992-03-19 | 1992-03-19 | Earset type handset |
| CA002094667A CA2094667A1 (en) | 1992-03-19 | 1993-04-22 | Two-way communications earset with filter |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2094667A1 true CA2094667A1 (en) | 1994-10-23 |
Family
ID=25676114
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002094667A Abandoned CA2094667A1 (en) | 1992-03-19 | 1993-04-22 | Two-way communications earset with filter |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0564874B1 (en) |
| JP (1) | JPH0817415B2 (en) |
| CA (1) | CA2094667A1 (en) |
| DE (1) | DE69313902T2 (en) |
| ES (1) | ES2108151T3 (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE69626848D1 (en) | 1995-12-22 | 2003-04-24 | Brueel & Kjaer Sound & Vibrati | SYSTEM AND METHOD FOR MEASURING A CONTINUOUS SIGNAL |
| US6175633B1 (en) | 1997-04-09 | 2001-01-16 | Cavcom, Inc. | Radio communications apparatus with attenuating ear pieces for high noise environments |
| US6885753B2 (en) | 2000-01-27 | 2005-04-26 | New Transducers Limited | Communication device using bone conduction |
| GB0024279D0 (en) * | 2000-10-04 | 2000-11-15 | New Transducers Ltd | Audio apparatus |
| GB0321617D0 (en) | 2003-09-10 | 2003-10-15 | New Transducers Ltd | Audio apparatus |
| EP2285135A1 (en) * | 2009-07-07 | 2011-02-16 | Nxp B.V. | Microphone-speaker device comprising a low pass filter |
| JP5646969B2 (en) * | 2010-11-24 | 2014-12-24 | 日立アプライアンス株式会社 | Air conditioner |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5525577Y2 (en) * | 1975-09-16 | 1980-06-19 | ||
| GB1530814A (en) * | 1977-06-20 | 1978-11-01 | British Aircraft Corp Ltd | Hearing protection devices |
| JPS58188996A (en) * | 1982-04-27 | 1983-11-04 | Katsuo Motoi | Two-way communication device in external auditory miatus |
| FR2595498B1 (en) * | 1986-03-07 | 1989-06-02 | Centre Nat Rech Scient | METHODS AND DEVICES FOR MITIGATING EXTERNAL NOISE ARISING AT TYMPAN AND IMPROVING THE INTELLIGIBILITY OF ELECTROACOUSTIC COMMUNICATIONS |
| DE3627002A1 (en) * | 1986-08-08 | 1988-02-18 | Philips Patentverwaltung | Method and circuit arrangement for acoustically compensating for the environmental noise in headphone reception |
-
1992
- 1992-03-19 JP JP4092457A patent/JPH0817415B2/en not_active Expired - Fee Related
-
1993
- 1993-03-19 EP EP93104560A patent/EP0564874B1/en not_active Expired - Lifetime
- 1993-03-19 DE DE69313902T patent/DE69313902T2/en not_active Expired - Fee Related
- 1993-03-19 ES ES93104560T patent/ES2108151T3/en not_active Expired - Lifetime
- 1993-04-22 CA CA002094667A patent/CA2094667A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| DE69313902T2 (en) | 1998-01-22 |
| ES2108151T3 (en) | 1997-12-16 |
| EP0564874A1 (en) | 1993-10-13 |
| EP0564874B1 (en) | 1997-09-17 |
| JPH0817415B2 (en) | 1996-02-21 |
| JPH05268310A (en) | 1993-10-15 |
| DE69313902D1 (en) | 1997-10-23 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |