IE55102B1 - Electro-acoustic transducer - Google Patents
Electro-acoustic transducerInfo
- Publication number
- IE55102B1 IE55102B1 IE16284A IE16284A IE55102B1 IE 55102 B1 IE55102 B1 IE 55102B1 IE 16284 A IE16284 A IE 16284A IE 16284 A IE16284 A IE 16284A IE 55102 B1 IE55102 B1 IE 55102B1
- Authority
- IE
- Ireland
- Prior art keywords
- diaphragm
- hole
- transducer
- coil
- tunnel
- Prior art date
Links
- 230000008878 coupling Effects 0.000 claims abstract description 3
- 238000010168 coupling process Methods 0.000 claims abstract description 3
- 238000005859 coupling reaction Methods 0.000 claims abstract description 3
- 230000002093 peripheral effect Effects 0.000 claims description 3
- 239000007787 solid Substances 0.000 claims description 2
- BGPVFRJUHWVFKM-UHFFFAOYSA-N N1=C2C=CC=CC2=[N+]([O-])C1(CC1)CCC21N=C1C=CC=CC1=[N+]2[O-] Chemical compound N1=C2C=CC=CC2=[N+]([O-])C1(CC1)CCC21N=C1C=CC=CC1=[N+]2[O-] BGPVFRJUHWVFKM-UHFFFAOYSA-N 0.000 claims 1
- 230000000694 effects Effects 0.000 abstract description 3
- 230000035945 sensitivity Effects 0.000 description 3
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 230000002452 interceptive effect Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229920001169 thermoplastic Polymers 0.000 description 1
- 239000004416 thermosoftening plastic Substances 0.000 description 1
- 238000003466 welding Methods 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
- H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
- H04R1/22—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only
- H04R1/225—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only for telephonic receivers
Landscapes
- Health & Medical Sciences (AREA)
- Otolaryngology (AREA)
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Acoustics & Sound (AREA)
- Signal Processing (AREA)
- Audible-Bandwidth Dynamoelectric Transducers Other Than Pickups (AREA)
- Electrostatic, Electromagnetic, Magneto- Strictive, And Variable-Resistance Transducers (AREA)
Abstract
In electro-acoustic transducers, especially for use in a telephone subscriber's instrument, to reduce the low frequency response of the transducer without increasing distortion one or more holes or tunnels (11) are provided through the diaphragm support member (5), the holes or tunnels coupling the air behind the diaphragm with the air in front. Such holes or tunnels can also be formed by a groove or grooves in the support member, the diaphragm rim then acting in effect as a lid for the or each such groove. The holes or tunnels do not have to be parallel to the plane of the diaphragm, and the idea is applicable to types of transducers other than the moving coil type. <IMAGE>
[GB2134745A]
Description
55102
This invention relates to electro-acoustic transducers, and especially to such transducers for use in telephone subscriber's instruments.
Such transducers often need a reduced 5 sensitivity at low frequency to prevent low frequency noise from interfering with the required signals, and in the case of telephone transducers both transmitters (microphones) and receivers (earphones) may require such low frequency sensitivity reduction. The usual way to 10 produce the drop in sensitivity is to make a small hole through the diaphragm. At low frequencies, air can pass through the diaphragm, so little energy is transferred between acoustic and electrical forms.' As the frequency increases the acoustic.mass of the hole increasingly 15 impedes the flow of air and the attenuation is reduced. However, the hole increases low frequency distortion, particularly in the region at which the reduction begins. This effect occurs both with transmitters and receivers, but the main problem is for receivers where 20 the diaphragm movements are larger. This suggests that the problem is due to the high particle velocity of air flowing through the hole, which must be small (diameter of the order of 0.7mm) to give the required frequency response. Thus the flow becomes turbulent and the 25 relationship between the pressure across the hole and the flow of air through the hole is non-linear. The distortion effect may also be partly due to relative - 2 - velocity between the air and diaphragm which, because the diaphragm is itself in motion, is greater than through a stationary hole.
An object of the invention is to provide a transducer in which the above difficulties are at least minimised. '
According to the invention there is provided an electro-acoustic transducer of the moving coil type, which includes a diaphragm unit including a diaphragm and coil and a magnet unit including a magnet and pole-pieces so located as to define an annular air gap in which the coil is located, wherein the diaphragm has a substantially circular central part and a substantially annular part so arranged that the coil is supported in the air gap by both parts of the diaphragm, wherein the outer part of the diaphragm is a flat annular part linked to the coil by a shallow coniform region, wherein the flat outer annular part is supported at its periphery by a stationary annular support member which is part of the casing of the transducer, wherein the magnet unit is wholly within said outer casing and includes a central member which carries a central pole-piece for the magnet unit, which central member is a solid cylindrical member, wherein one or more holes or tunnels are provided in the support member, the or each said hole or tunnel having its axis substantially parallel to the plane of said outer peripheral region and adjacent to that region, wherein each said hole or tunnel has its width short compared with its length, and wherein the or each said hole or tunnel couples the air in a region within the outer casing and in front of the diaphragm with the air in a region also within the outer casing and behind the diaphragm, which coupling is effected round the outermost periphery of the diaphragm.
Thus we have one or more holes or tunnels through the support for the diaphragm. As the path for the air to travel through these holes or slots is longer than that though the thickness of the diaphragm, 5 they have a larger total cross-sectional area than the prior art diaphragm hole to produce the same low frequency cut. The larger area results in lower relative air velocities, as does the fact that the holes are stationary. Thus the longer holes or tunnels 10 have greater acoustic resistance, which reduces distortion.
He have found that the harmonic distortion is reduced by these means from 7% to less than 1.5% in a preferred embodiment of the invention.
There follows a detailed description with reference to Figures 1 and 2 of the accompanying drawings of two implementations of this invention.
Both are moving coil types of the sort described in our British Patent Specification Ho. 2114855 B, but the invention 20 is also applicable to other types of transducer.
The first form is 3hown in Figure 1. It consists of a moving coil transducer arrangement having a magnetic assembly formed by the magnet 1, ring 2, inner pole 3 and outer pole-piece 4. The air gap for 25 the coil is between the ring 2 and the inner pole.3.
The magnetic assembly is mounted in a support ring 5 and is held in place by the rear cover 6. The diaphragm 7 supports the coil 8, which is movable in the annular gap between ring 2 and inner pole-piece 3.
The transducer is completed by terminals 9 and front cover 10. In practice acoustic resistance may be included to produce a smooth frequency response, but the means of providing this is not shown. Further details of such a transducer will be found in the 35 above-mentioned application. Instead of the normal hole through the diaphragm, the volumes on either side - 4 - of the diaphragm are connected by holes 11 through the support ring 5. Only one such hole is shown but more may be provided if this is found to be desirable.
In an alternative, and preferred arrangement, see Figure 2 the hole is replaced by one or more slots 12 formed by grooves in the upper surface of the support ring 5 and the diaphragm 7. This method is preferred because when the support ring 5 is a thermo-plastics moulding the manufacturing tooling is simpler and the part less expensive.
Both versions have the diaphragm attached to the support ring by adhesive or welding. The invention may also be applied when the diaphragm is clamped in place. The grooves or radial holes are then needed in the clamping members on each side of the diaphragm.
The invention can also be applied to a moving coil transducer in which the diaphragm rim is clamped between two members; however, in this case the holes or grooves or slots are provided in both of those members.
It will be noted that, as in the transducer described in the above-quoted patent specification, the diaphragm is in both embodiments of the invention, in two parts, one of which is a circular central part and the other is an annular part, the coil being carried by the central part and attached to the outer part. The outer periphery of the outer part is supported on a stationary support ring member 5.
Claims (5)
1. An electro-acoustic transducer of the moving coil type, which includes a diaphragm unit including a diaphragm and coil and a magnet unit including a magnet 5 and pole-pieces so located as to define an annular air gap in which the coil is located, wherein the diaphragm has a substantially circular central part and a substantially annular part so arranged that the coil is supported in the air gap by both parts of the diaphragm, 10 wherein the outer part of the diaphragm is a flat annular part linked to the coil by a shallow coniform region, wherein the flat outer annular part is supported at its periphery by a stationary annular support member which is part of the casing of the transducer, wherein the magnet 15 unit is wholly within said outer casing and includes a central member which carries a central pole-piece for the magnet unit, which central member is a solid cylindrical member, wherein one or more holes or tunnels are provided in the support member, the or each said hole or tunnel 20 having its axis substantially parallel to the plane of said outer peripheral region and adjacent to that region, wherein each said hole or tunnel has its width short compared with its length, and wherein the or each said hole or tunnel couples the air in a region within the 25 outer casing and in front of the diaphragm with the air in a region also within the outer casing and behind the diaphragm, which coupling is effected round the outermost periphery of the diaphragm.
2. A transducer as claimed in claim 1, wherein the 30 or each said hole or tunnel is formed within the diaphragm support .
3. A transducer as claimed in claim 1, wherein the or each said hole or tunnel is a groove in the diaphragm support member which is closed or partly closed by the 35 peripheral rim of the diaphragm.
4. An electro-acoustic transducer, substantially as described with reference to Figure 1 or Figure 2 of the accompanying drawings. MACLACHLAN & DONALDSON Applicants' Agents,
5. 47 Merrion Square, DUBLIN 2.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB08303131A GB2134745B (en) | 1983-02-04 | 1983-02-04 | Electro acoustic tranducer |
Publications (2)
Publication Number | Publication Date |
---|---|
IE840162L IE840162L (en) | 1984-08-04 |
IE55102B1 true IE55102B1 (en) | 1990-05-23 |
Family
ID=10537478
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
IE16284A IE55102B1 (en) | 1983-02-04 | 1984-01-25 | Electro-acoustic transducer |
Country Status (6)
Country | Link |
---|---|
AU (1) | AU569275B2 (en) |
GB (1) | GB2134745B (en) |
HK (1) | HK76187A (en) |
IE (1) | IE55102B1 (en) |
NZ (1) | NZ206899A (en) |
SG (1) | SG40087G (en) |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3700594A1 (en) * | 1986-01-16 | 1987-07-23 | Akg Akustische Kino Geraete | PRESSURE GRADIENT RECEIVER |
GB8727072D0 (en) * | 1987-11-19 | 1987-12-23 | British Telecomm | Moisture barrier assembly |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB388069A (en) * | 1929-05-15 | 1933-02-20 | Electrical Res Prod Inc | Improvements in electrodynamic devices for use in receiving or transmitting sound |
GB409368A (en) * | 1932-04-12 | 1934-04-30 | Electrical Res Prod Inc | Improvements in or relating to acoustic devices of the electrodynamic type |
AT274916B (en) * | 1966-02-14 | 1969-10-10 | Elektroakusztikai Gyar | Dynamic microphone |
GB1350122A (en) * | 1970-10-29 | 1974-04-18 | Electronic Res Ass | Sound reproducing equipment |
NL7105001A (en) * | 1971-04-14 | 1972-10-17 | ||
US3940575A (en) * | 1975-03-03 | 1976-02-24 | Cbs Inc. | Directional microphone |
EP0040948B1 (en) * | 1980-05-23 | 1984-10-31 | International Standard Electric Corporation | Method of making an electro dynamic transducer |
GB2114855B (en) * | 1982-02-09 | 1985-10-23 | Standard Telephones Cables Ltd | Moving coil transducer |
-
1983
- 1983-02-04 GB GB08303131A patent/GB2134745B/en not_active Expired
-
1984
- 1984-01-20 NZ NZ20689984A patent/NZ206899A/en unknown
- 1984-01-25 IE IE16284A patent/IE55102B1/en unknown
- 1984-02-01 AU AU23942/84A patent/AU569275B2/en not_active Ceased
-
1987
- 1987-05-04 SG SG40087A patent/SG40087G/en unknown
- 1987-10-15 HK HK76187A patent/HK76187A/en unknown
Also Published As
Publication number | Publication date |
---|---|
NZ206899A (en) | 1987-10-30 |
GB8303131D0 (en) | 1983-03-09 |
GB2134745A (en) | 1984-08-15 |
HK76187A (en) | 1987-10-23 |
AU569275B2 (en) | 1988-01-28 |
AU2394284A (en) | 1984-08-09 |
GB2134745B (en) | 1986-10-22 |
IE840162L (en) | 1984-08-04 |
SG40087G (en) | 1987-07-24 |
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