Electrical audio signal processing systems and devices – Electro-acoustic audio transducer
Patent
1994-08-01
1996-11-26
Kuntz, Curtis
Electrical audio signal processing systems and devices
Electro-acoustic audio transducer
381169, 381189, 181138, 181198, H04R 2500
Patent
active
055793983
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to electro-acoustic transducers and particularly, but not exclusively, to such transducers in the form of ear pieces for telephone headsets and the like.
BACKGROUND PRIOR ART
Telephone operators often build up very substantial static voltages on their bodies, particularly if they are imprudent enough to wear man-made fibers. If they then plug their headset into the telephone exchange apparatus, it is not uncommon for a spark to jump from their ear through the acoustic inlets in the ear piece to a grounded metal portion of the transducer. As these sparks can be derived from several thousands of volts, the sensation is at best uncomfortable. This problem particularly arises in small devices where distances between the acoustic inlets and grounded portions of transducers are normally extremely small. Additionally, it has been found difficult to produce economically and compactly a suitable method of boosting the bass response of such ear pieces.
The present invention is provided to solve these and other problems.
SUMMARY OF THE INVENTION
From one aspect the invention consists in an electro-acoustic transducer including a body defining a chamber, a diaphragm extending across at least part of the chamber to define front and rear portions, a main acoustic inlet/outlet connected to the front portion and a Thuras tube connecting the rear portion and the main inlet/outlet, wherein at least a portion of the Thuras tube is defined by an end piece forming a wall of the chamber.
In a preferred embodiment, the end piece further defines the main acoustic inlet/outlet, and the Thuras tube may be formed as a channel in that end piece. Particularly conveniently the transducer may further include a cap overlying the end piece with subsidiary inlet/outlets formed therein and offset from the main inlet/outlet. In this case the end cap may close off the channel to complete the tube.
The end cap and end piece may together define an extended air path between the subsidiary inlet/outlets and a grounded metal part within the chamber. Current designs simply have these inlets and outlets passing straight through the cap into the chamber, although sometimes there are guards to prevent mechanical damage due to penetration through these holes.
From another aspect there is provided an electro-acoustic transducer having a chamber including a grounded metal part, a non-electrically conducting cover defining a number of subsidiary acoustic inlet/outlets and a main acoustic inlet/outlet for the chamber wherein the cover defines an extended air path between the subsidiary outlets and a grounded metal part within.
As has been mentioned above, this extended path reduces the risk of electrical discharge occurring along the path typically for potential differences of up to 15,000 volts D.C.
Preferably the chamber is generally cylindrical, the main inlet/outlet is at or adjacent the axis of the chamber, the subsidiary inlets/outlets are radially offset therefrom and the main inlet/outlet is defined in the wall extending across the chamber.
Particularly conveniently the subsidiary inlets/outlets are formed in an end cap which overlies the wall and a part of the air path is defined between the air cap and the wall.
Although the invention has been defined, it is to be understood that the invention includes any inventive combination of the features set out above or in the following description.
The invention may be performed in various ways and a specific embodiment will now be described, by way of example, with reference to the accompanying drawings.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is an exploded view of an electro-acoustic transducer;
FIG. 2 is a more detailed view from above of an end piece of the transducer, and
FIG. 3 is a diagrammatic cross-sectional view of the upper part of the transducer demonstrating a discharge path.
DETAILED DESCRIPTION
While this invention is susceptible of embodiments in many different forms, there is shown in the drawings and will herein be described in detail, a
REFERENCES:
patent: 3588383 (1971-06-01), Carlson et al.
patent: 4239945 (1980-12-01), Atoji et al.
patent: 4796288 (1989-01-01), Busche et al.
patent: 4843628 (1989-06-01), Hofer
patent: 5410608 (1995-04-01), Lucey et al.
Knowles Electronics Co.
Kuntz Curtis
Mei Xu
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