CA2023142A1 - High compliance headphone driving - Google Patents
High compliance headphone drivingInfo
- Publication number
- CA2023142A1 CA2023142A1 CA002023142A CA2023142A CA2023142A1 CA 2023142 A1 CA2023142 A1 CA 2023142A1 CA 002023142 A CA002023142 A CA 002023142A CA 2023142 A CA2023142 A CA 2023142A CA 2023142 A1 CA2023142 A1 CA 2023142A1
- Authority
- CA
- Canada
- Prior art keywords
- diaphragm
- driver
- headset
- set forth
- voice coil
- 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
- 238000007373 indentation Methods 0.000 claims abstract description 4
- 239000004033 plastic Substances 0.000 claims description 7
- 230000009467 reduction Effects 0.000 claims description 6
- 239000002991 molded plastic Substances 0.000 claims 1
- 210000003128 head Anatomy 0.000 description 7
- 230000005540 biological transmission Effects 0.000 description 4
- 230000008859 change Effects 0.000 description 3
- 230000008901 benefit Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000006870 function Effects 0.000 description 2
- 229920002799 BoPET Polymers 0.000 description 1
- 239000005041 Mylar™ Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 210000000613 ear canal Anatomy 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 239000002985 plastic film Substances 0.000 description 1
- 229920006255 plastic film Polymers 0.000 description 1
- 230000001012 protector Effects 0.000 description 1
Classifications
-
- 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
- H04R1/1083—Reduction of ambient noise
-
- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
- G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
- G10K11/1785—Methods, e.g. algorithms; Devices
- G10K11/17857—Geometric disposition, e.g. placement of microphones
-
- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
- G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
- G10K11/1785—Methods, e.g. algorithms; Devices
- G10K11/17861—Methods, e.g. algorithms; Devices using additional means for damping sound, e.g. using sound absorbing panels
-
- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
- G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
- G10K11/1787—General system configurations
-
- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
- G10K2210/10—Applications
- G10K2210/108—Communication systems, e.g. where useful sound is kept and noise is cancelled
- G10K2210/1081—Earphones, e.g. for telephones, ear protectors or headsets
-
- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
- G10K2210/30—Means
- G10K2210/321—Physical
- G10K2210/3217—Collocated sensor and cancelling actuator, e.g. "virtual earth" designs
-
- 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
- H04R1/1008—Earpieces of the supra-aural or circum-aural type
Landscapes
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Acoustics & Sound (AREA)
- Multimedia (AREA)
- Signal Processing (AREA)
- Headphones And Earphones (AREA)
- Measurement Of Velocity Or Position Using Acoustic Or Ultrasonic Waves (AREA)
- Electroluminescent Light Sources (AREA)
Abstract
Abstract An active noise reducing headset has a high compliance diaphragm. Structure limits the maximum excursion of the diaphram so that the voice coil does not escape the air gap. Structure, such as indentations in the diaphragm, prevent unrecoverable diaphragm collapse.
Description
- - ` 202~142 .. . ,....... .. ,~
. 0649C AABOSQO4 .. .
HIGH COMPLIANCE HEADPHONE DRIVING
Backqround of the Invention The present invention relates to high compliance drivers in active noise reducing headsets.
Particularly, it relates to an apparatus for protecting the driver diaphragm.
In active noise reducing headphones it is known to use a headphone having front (inside) and rear (outside) cavities separated by a baffle carrying a small driver.
According to the invention, the driver is a high compliance driver. According to another feature of the invention, there is structure limiting the maximum excursion of the diaphragm. According to another feature of the invention, the diaphragm is formed with indentations having a component transverse to the circular grooves or corrugations near the diapnragm periphery. According to another aspect of the invention, the basket surface under the diaphragm has raised portions.
Other features and advantages of the invention will become apparent from the following detailed description when read in connection with the accompanying drawing the single figure of which is a plan view of a high compliance driver with the headphone ~; cup generally illustrated to show the environment of the invention.
With reference now to the drawing, there is shown an embodiment of the invention. The invention includes a baffle 11 that separates a front or inside cavity from .; , . '~ . . ,:. . ;
. . ~ .
,; ~ ' ' 2~23142 ?.
a rear or outside cavity and carries high compliance driver 13 having diaphragm 14. Plastic fingers 15 are equi-angularly spaced about the driver axis, extend radially inward and are positioned along the driver axial direction of motion so as to limit displacement of the diaphragm from its center or rest position to a plane sufficiently close to the rest plane with the diaphragm centered so that a portion of the voice coil is always in the air gap and sufficiently far from the central plane so that the diaphragm is free to translate axially without obstruction when normally reproducing sound with the headphones properly mounted on the head of the user. An active noise reduction system mounting structure 16 carries a microphone (not shown) near the diaphragm used with associated electronic circuitry comprising a system corresponding substantially to the active noise reducing system disclosed in U.S. Patent Nos. 4,644,581 and 4,455,675 incorporated herein by reference.
Having described the physical arrangement of an exemplary embodiment, it is appropriate to consider certain principles. It is convenient to refer to the cavity nearer the user and encompassing his ear with headphones properly positioned as the front or inside cavity and the cavity further from the user as the rear or outside cavity. It is desirable to keep the front cavity volume as small as practical to maximize the sound pressure that the small driver produces at the ear canal to cancel low frequency noise. However, to increase passive transmission attenuation for ambient noise penetrating an ear cup sealed around the ear by a cushion, it is desirable to make the front cavity volume large. ~ .
~, , . , ,.~ .
.~ . .
.. . , , ~ ~
- ~ 2~23~
. . .
It has been discovered that the effective air volume which determines this transmission attenuation is not simply the volume of the front cavity but also a function of the driver compliance (below its free air resonance frequency) and the volume of the rear cavity.
If Cf is the compliance of the front cavity air volume, Cr is the compliance of the rear cavity air volume and Cd is the compliance of the driver, then the effective co~pliance Ceff determining passive transmission attenuation is the front cavity compliance in series with the parallel combination of the driver compliance and the rear cavity compliance, or Ceff Cf + CrCd/(Cr + Cd) below the free air resonance of the driver.
Since compliance of an enclosed quantity of air is proportional to the volume, for a given ear cup volume divided into front and rear cavities, it can be shown that the effective compliance Ceff is maximized by maximizing the driver compliance. Thus, a driver with very high compliance (low stiffness) and low mass (so as to resonate with the high compliance at as high a frequency as practical), effects significant improvements in passive transmission attenuation below driver free air resonance without audibly affecting sound reprodution. In the limit, if the compiiance of the driver is much greater than the compliance of the air in the rear cavity, the effective compliance is equal to the sum of the rear cavity and front cavity compliances, Cf + Cr.
High compliance herein means the driver compliance is greater than the rear cavity compliance. -Another advantage of high compliance drivers is that at very low frequencies (below the rear cavity port resonance when the rear cavity is ported), higher driver ~. ~
: , ~Q2'3~42 ~ ..~.
- _ 4 _ compliance results in higher system efficiency. This increase in efficiency reduces the electrical power required to generate sound pressures needed to cancel high levels of low freguency noise. This feature is particularly advantageous in battery-powered active noise reduction headsets and hearing protectors.
When the ear opening in the headset is sealed against the head or any other surface, motion of the earcup relative to that surface changes the volume of the front cavity. Slight changes in volume result in tremendous subsonic pressures. If the volume is increased, such as when the earcup is removed from the head after the cushion was sealed tightly to the head, the under-pressure generated tends to pull the driver diaphragm toward the opened end of the earcup. Since high compliance, low mass drivers move very freely, this pressure can very easily pull the voice coil outside of the gap beyond its normal maximum range of excursion, with the risk that it may catch on the driver basket or magnet and not return to its nominal rest position upon release of the under-pressure. If the volume is decreased, such as when the earcup is pushed suddenly against the head, the over-pressurè generated can cause the thin, flexible diaphragm to collapse from its normal shape. Drivers with diaphragms formed from thin plastic films usually are formed with angled grooves or corrugations in the outer annulus between the voice coil and the edge of the diaphragm. These grooves expand and contract as the voice coil moves and help assure linearly, piston-like motion. Under the over-pressure `~ conditions described above, these grooves may irreversably change shape, and prevent the driver diaphragm from returning to its norm,al~shape and position.
.~
:-. : 1 r ~ ......................... 2 0 2 3 1 4 2 ~. ,_.
The invention avoids the suction orunder-pressure problem by locating a structure in the earcup over the diaphragm to limit voice coil excursion. This structure lS is positioned such that, during the normal range of excursion of the driver diaphragm, the diaphragm does not touch structure 15 and motion is unimpeded. Structure lS is located close enough to the driver such that it contacts the diaphragm before it is pulled so far that the voice coil is pulled fully from the gap. Since the voice coil is not pulled from the gap, when the suction is released, the coil will return to its normal rest position and not hang up on the basket. The structure lS is preferably small enough so that it does not cause diffraction or otherwise affect the sound pressure detected by the active noise reduction system's microphone except at high requencies (above lOKHz~. The present invention accomplishes this by using three small fingers of plastic 16 positioned to symmetrically contact the diaphragm along the circle where the voice coil is glued to it. Contacting the diaphragm with small point~ e fingers anywhere but along the voice coil might risk possibly puncturing or otherwise damaging the diaphragm. An alternative embodiment for the structure to stop diaphragm motion is a fine wire mesh screen 16 shaped so as to contact as much of the surface of the diaphragm as possible at its position of maximum allowed outward excursion. ~3y contacting over a large area, the pressure at any point is small enough so as not to damage the driver.
The present invention avoids the driver collapse or over-pressure problem by using a driver whose diaphragm recovers its shape ~he~ collapsed. Changing the shape of the grooves or corrugations by including ,'.~ ' , : , ,.
;
. ~ .. .
;: ' .
20231~2 . ~ ,~-, indentations 17, having a radial component in the diaphragm such.that the diaphragm recovers i~s shape if collapsed, prevents unrecoverable collapse. An alternative solution is to change the shape of the metal basket to which the diaphragm is attached or to add a structure to the basket. Commonly the basket surface under the diaphragm is flat. By raising this surface at some points it can be made to support the diaphragm in over-pressure situations, preventing it from collapsing to the point that permanent damage or change in shape occurs.
A preferred form of the invention involves combining the driver mounting structure, active noise reduction system microphone mounting structure, and 1'5 driver under-pressure excursion stops into a single plastic piece molded in one shot This approach reduces the effect of mechanical tolerance build-up and positions all parts accurately so as to provide consistent performance, This structure could be further combined with the baffle separating front and rear cavities.
The specific apparatus functions as follows When the headset is removed from the head causing an under-pressure situation, limitation'elements 15 limit the excursion of diaphrasm 14 so that the voice coil doesn't escape the air gap. This structure ensures that diaphragm lg will return to its nominal position. These .- limitation elements 15 do not interfere with the normal ;~ range of motion of diaphragm 14.
;~ 30 In an over-pressure situation such as when the headset is pressed against the head, grooves 17 in the surface of diaphragm 14 cause the diaphrasm 14 to recover its original shape iffco~lapsed by the increase '~` in pressure. In another embodiment, raised points ' .
.
. .
~ 2023~12 ~~
. . .
underneath the diaphragm 14 support it during over-pressure situations preventing a collapse.
. In a specific embodiment of the invention, the front cavity volume is approximately lOOcc (cubic centimeters), and the rear cavity volume is also loocc.
The driver has a free air resonance of 250 Hz and an acoustical compliance of lx10 9 (meters)5/(Newtons).
This compliance is equivalent to a volume of 150cc of air. The effective volume is thus Veff = 100+100*150/(100+150) = 160cc.
The driver diaphragm is formed of mylar which is 1 mil thicX. The driver is mounted in a plastic baffle with three under-pressure excursion stops placed to contact the diaphragm at approximately 30 mils excursion. Under maximum operating conditions (high noise and communication levels) driver excursion does not exceed 20 mils. Rear cavity port tuning is set to 90 Hz. Port tuning is chosen based on need for increased driver output for noise cancellation in 50 - 80 Hz range wi~hout compromising passive attenuation. A much larger rear cavity would eliminate need for a port in rear cavity, but would compr~mise styling.
~ ' t ,,, ' ' ' .
' '
. 0649C AABOSQO4 .. .
HIGH COMPLIANCE HEADPHONE DRIVING
Backqround of the Invention The present invention relates to high compliance drivers in active noise reducing headsets.
Particularly, it relates to an apparatus for protecting the driver diaphragm.
In active noise reducing headphones it is known to use a headphone having front (inside) and rear (outside) cavities separated by a baffle carrying a small driver.
According to the invention, the driver is a high compliance driver. According to another feature of the invention, there is structure limiting the maximum excursion of the diaphragm. According to another feature of the invention, the diaphragm is formed with indentations having a component transverse to the circular grooves or corrugations near the diapnragm periphery. According to another aspect of the invention, the basket surface under the diaphragm has raised portions.
Other features and advantages of the invention will become apparent from the following detailed description when read in connection with the accompanying drawing the single figure of which is a plan view of a high compliance driver with the headphone ~; cup generally illustrated to show the environment of the invention.
With reference now to the drawing, there is shown an embodiment of the invention. The invention includes a baffle 11 that separates a front or inside cavity from .; , . '~ . . ,:. . ;
. . ~ .
,; ~ ' ' 2~23142 ?.
a rear or outside cavity and carries high compliance driver 13 having diaphragm 14. Plastic fingers 15 are equi-angularly spaced about the driver axis, extend radially inward and are positioned along the driver axial direction of motion so as to limit displacement of the diaphragm from its center or rest position to a plane sufficiently close to the rest plane with the diaphragm centered so that a portion of the voice coil is always in the air gap and sufficiently far from the central plane so that the diaphragm is free to translate axially without obstruction when normally reproducing sound with the headphones properly mounted on the head of the user. An active noise reduction system mounting structure 16 carries a microphone (not shown) near the diaphragm used with associated electronic circuitry comprising a system corresponding substantially to the active noise reducing system disclosed in U.S. Patent Nos. 4,644,581 and 4,455,675 incorporated herein by reference.
Having described the physical arrangement of an exemplary embodiment, it is appropriate to consider certain principles. It is convenient to refer to the cavity nearer the user and encompassing his ear with headphones properly positioned as the front or inside cavity and the cavity further from the user as the rear or outside cavity. It is desirable to keep the front cavity volume as small as practical to maximize the sound pressure that the small driver produces at the ear canal to cancel low frequency noise. However, to increase passive transmission attenuation for ambient noise penetrating an ear cup sealed around the ear by a cushion, it is desirable to make the front cavity volume large. ~ .
~, , . , ,.~ .
.~ . .
.. . , , ~ ~
- ~ 2~23~
. . .
It has been discovered that the effective air volume which determines this transmission attenuation is not simply the volume of the front cavity but also a function of the driver compliance (below its free air resonance frequency) and the volume of the rear cavity.
If Cf is the compliance of the front cavity air volume, Cr is the compliance of the rear cavity air volume and Cd is the compliance of the driver, then the effective co~pliance Ceff determining passive transmission attenuation is the front cavity compliance in series with the parallel combination of the driver compliance and the rear cavity compliance, or Ceff Cf + CrCd/(Cr + Cd) below the free air resonance of the driver.
Since compliance of an enclosed quantity of air is proportional to the volume, for a given ear cup volume divided into front and rear cavities, it can be shown that the effective compliance Ceff is maximized by maximizing the driver compliance. Thus, a driver with very high compliance (low stiffness) and low mass (so as to resonate with the high compliance at as high a frequency as practical), effects significant improvements in passive transmission attenuation below driver free air resonance without audibly affecting sound reprodution. In the limit, if the compiiance of the driver is much greater than the compliance of the air in the rear cavity, the effective compliance is equal to the sum of the rear cavity and front cavity compliances, Cf + Cr.
High compliance herein means the driver compliance is greater than the rear cavity compliance. -Another advantage of high compliance drivers is that at very low frequencies (below the rear cavity port resonance when the rear cavity is ported), higher driver ~. ~
: , ~Q2'3~42 ~ ..~.
- _ 4 _ compliance results in higher system efficiency. This increase in efficiency reduces the electrical power required to generate sound pressures needed to cancel high levels of low freguency noise. This feature is particularly advantageous in battery-powered active noise reduction headsets and hearing protectors.
When the ear opening in the headset is sealed against the head or any other surface, motion of the earcup relative to that surface changes the volume of the front cavity. Slight changes in volume result in tremendous subsonic pressures. If the volume is increased, such as when the earcup is removed from the head after the cushion was sealed tightly to the head, the under-pressure generated tends to pull the driver diaphragm toward the opened end of the earcup. Since high compliance, low mass drivers move very freely, this pressure can very easily pull the voice coil outside of the gap beyond its normal maximum range of excursion, with the risk that it may catch on the driver basket or magnet and not return to its nominal rest position upon release of the under-pressure. If the volume is decreased, such as when the earcup is pushed suddenly against the head, the over-pressurè generated can cause the thin, flexible diaphragm to collapse from its normal shape. Drivers with diaphragms formed from thin plastic films usually are formed with angled grooves or corrugations in the outer annulus between the voice coil and the edge of the diaphragm. These grooves expand and contract as the voice coil moves and help assure linearly, piston-like motion. Under the over-pressure `~ conditions described above, these grooves may irreversably change shape, and prevent the driver diaphragm from returning to its norm,al~shape and position.
.~
:-. : 1 r ~ ......................... 2 0 2 3 1 4 2 ~. ,_.
The invention avoids the suction orunder-pressure problem by locating a structure in the earcup over the diaphragm to limit voice coil excursion. This structure lS is positioned such that, during the normal range of excursion of the driver diaphragm, the diaphragm does not touch structure 15 and motion is unimpeded. Structure lS is located close enough to the driver such that it contacts the diaphragm before it is pulled so far that the voice coil is pulled fully from the gap. Since the voice coil is not pulled from the gap, when the suction is released, the coil will return to its normal rest position and not hang up on the basket. The structure lS is preferably small enough so that it does not cause diffraction or otherwise affect the sound pressure detected by the active noise reduction system's microphone except at high requencies (above lOKHz~. The present invention accomplishes this by using three small fingers of plastic 16 positioned to symmetrically contact the diaphragm along the circle where the voice coil is glued to it. Contacting the diaphragm with small point~ e fingers anywhere but along the voice coil might risk possibly puncturing or otherwise damaging the diaphragm. An alternative embodiment for the structure to stop diaphragm motion is a fine wire mesh screen 16 shaped so as to contact as much of the surface of the diaphragm as possible at its position of maximum allowed outward excursion. ~3y contacting over a large area, the pressure at any point is small enough so as not to damage the driver.
The present invention avoids the driver collapse or over-pressure problem by using a driver whose diaphragm recovers its shape ~he~ collapsed. Changing the shape of the grooves or corrugations by including ,'.~ ' , : , ,.
;
. ~ .. .
;: ' .
20231~2 . ~ ,~-, indentations 17, having a radial component in the diaphragm such.that the diaphragm recovers i~s shape if collapsed, prevents unrecoverable collapse. An alternative solution is to change the shape of the metal basket to which the diaphragm is attached or to add a structure to the basket. Commonly the basket surface under the diaphragm is flat. By raising this surface at some points it can be made to support the diaphragm in over-pressure situations, preventing it from collapsing to the point that permanent damage or change in shape occurs.
A preferred form of the invention involves combining the driver mounting structure, active noise reduction system microphone mounting structure, and 1'5 driver under-pressure excursion stops into a single plastic piece molded in one shot This approach reduces the effect of mechanical tolerance build-up and positions all parts accurately so as to provide consistent performance, This structure could be further combined with the baffle separating front and rear cavities.
The specific apparatus functions as follows When the headset is removed from the head causing an under-pressure situation, limitation'elements 15 limit the excursion of diaphrasm 14 so that the voice coil doesn't escape the air gap. This structure ensures that diaphragm lg will return to its nominal position. These .- limitation elements 15 do not interfere with the normal ;~ range of motion of diaphragm 14.
;~ 30 In an over-pressure situation such as when the headset is pressed against the head, grooves 17 in the surface of diaphragm 14 cause the diaphrasm 14 to recover its original shape iffco~lapsed by the increase '~` in pressure. In another embodiment, raised points ' .
.
. .
~ 2023~12 ~~
. . .
underneath the diaphragm 14 support it during over-pressure situations preventing a collapse.
. In a specific embodiment of the invention, the front cavity volume is approximately lOOcc (cubic centimeters), and the rear cavity volume is also loocc.
The driver has a free air resonance of 250 Hz and an acoustical compliance of lx10 9 (meters)5/(Newtons).
This compliance is equivalent to a volume of 150cc of air. The effective volume is thus Veff = 100+100*150/(100+150) = 160cc.
The driver diaphragm is formed of mylar which is 1 mil thicX. The driver is mounted in a plastic baffle with three under-pressure excursion stops placed to contact the diaphragm at approximately 30 mils excursion. Under maximum operating conditions (high noise and communication levels) driver excursion does not exceed 20 mils. Rear cavity port tuning is set to 90 Hz. Port tuning is chosen based on need for increased driver output for noise cancellation in 50 - 80 Hz range wi~hout compromising passive attenuation. A much larger rear cavity would eliminate need for a port in rear cavity, but would compr~mise styling.
~ ' t ,,, ' ' ' .
' '
Claims (7)
1. A headset comprising:
at least one earcup having a front and rear cavity, a baffle separating the front and rear cavities, a high compliance driver having a diaphragm joined to a voice coil normally residing in a gap mounted on the baffle, and an active noise reduction system,
at least one earcup having a front and rear cavity, a baffle separating the front and rear cavities, a high compliance driver having a diaphragm joined to a voice coil normally residing in a gap mounted on the baffle, and an active noise reduction system,
2. A headset in accordance with claim 1 and further comprising limiting structure limiting the maximum excursion of the diaphragm so that the voice coil remains at least partially in said gap.
3. The headset set forth in claim 2 wherein said limiting structure comprises a plurality of plastic elements, placed such that said plastic elements contact the diaphragm where the voice coil is joined to said diaphragm.
4. The headset set forth in claim 2 wherein the active noise reduction system mounting structure, the driver mounting structure, the baffle and the plastic elements are combined in a single piece of molded plastic.
5. The headset set forth in claim 2 wherein said limiting structure comprises a fine wire mesh screen shaped so as to contact as much of the surface of the diaphragm as practical at its position of maximum allowed outward excursion, preventing further movement.
6. The headset set forth in claim 1 and further comprising means for recovering from collapse of the diaphragm including indentations, in the diaphragm such that the diaphragm recovers its shape if collapsed.
7. The headset set forth in claim 1 and further comprising raised portions on the surface underneath the diaphragm preventing unrecoverable collapse of said diaphragm.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US39813389A | 1989-08-23 | 1989-08-23 | |
| US398,133 | 1989-08-23 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2023142A1 true CA2023142A1 (en) | 1991-02-24 |
Family
ID=23574122
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002023142A Abandoned CA2023142A1 (en) | 1989-08-23 | 1990-08-13 | High compliance headphone driving |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0414479B1 (en) |
| JP (1) | JP3268774B2 (en) |
| AT (1) | ATE128592T1 (en) |
| CA (1) | CA2023142A1 (en) |
| DE (1) | DE69022672T2 (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5265373B2 (en) | 2005-11-11 | 2013-08-14 | フィテック システムズ リミテッド | Noise elimination earphone |
| NZ584418A (en) | 2007-10-02 | 2012-12-21 | Phitek Systems Ltd | Component for noise reducing earphone |
| US9818394B2 (en) | 2009-11-30 | 2017-11-14 | Graeme Colin Fuller | Realisation of controller transfer function for active noise cancellation |
| CN102939691B (en) | 2010-05-17 | 2015-08-05 | 泰雷兹航空电子公司 | Airline passenger seat modular user interface device |
| EP2471710A1 (en) | 2010-11-15 | 2012-07-04 | Nigel Greig | Media distribution system |
| CN103748903B (en) | 2011-06-01 | 2017-02-22 | 菲泰克系统有限公司 | In-ear device incorporating active noise reduction |
| TWI551152B (en) * | 2013-05-08 | 2016-09-21 | 寶德科技股份有限公司 | Headphone with passive sound film |
| JP6336613B2 (en) * | 2014-03-17 | 2018-06-06 | ボーズ・コーポレーションＢｏｓｅ Ｃｏｒｐｏｒａｔｉｏｎ | Headset porting |
| FR3044197A1 (en) | 2015-11-19 | 2017-05-26 | Parrot | AUDIO HELMET WITH ACTIVE NOISE CONTROL, ANTI-OCCLUSION CONTROL AND CANCELLATION OF PASSIVE ATTENUATION, BASED ON THE PRESENCE OR ABSENCE OF A VOICE ACTIVITY BY THE HELMET USER. |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1807225A (en) * | 1928-03-09 | 1931-05-26 | Utah Radio Products Company In | Sound propagating diaphragm |
| NL257376A (en) * | 1959-10-29 | |||
| US4581496A (en) * | 1979-09-04 | 1986-04-08 | Emhart Industries, Inc. | Diaphragm for attenuating harmonic response in an electroacoustic transducer |
| NL8202529A (en) * | 1982-06-23 | 1984-01-16 | Philips Nv | ELECTRO-ACOUSTIC CONVERTER WITH A LONG STROKE. |
| GB8506860D0 (en) * | 1985-03-16 | 1985-04-17 | Plessey Co Plc | Noise reduction arrangements |
| GB8607047D0 (en) * | 1986-03-21 | 1986-04-30 | Univ Southampton | Acoustic noise reduction |
-
1990
- 1990-08-13 CA CA002023142A patent/CA2023142A1/en not_active Abandoned
- 1990-08-21 DE DE69022672T patent/DE69022672T2/en not_active Revoked
- 1990-08-21 AT AT90309125T patent/ATE128592T1/en active
- 1990-08-21 EP EP90309125A patent/EP0414479B1/en not_active Revoked
- 1990-08-23 JP JP22231790A patent/JP3268774B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| EP0414479A2 (en) | 1991-02-27 |
| JP3268774B2 (en) | 2002-03-25 |
| EP0414479A3 (en) | 1991-11-06 |
| DE69022672T2 (en) | 1996-03-07 |
| DE69022672D1 (en) | 1995-11-02 |
| EP0414479B1 (en) | 1995-09-27 |
| JPH03165694A (en) | 1991-07-17 |
| ATE128592T1 (en) | 1995-10-15 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |