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| Blind fastener |
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| Elliptically shaped transducer enclosure |
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| Acoustic trap for discharging fire arms |
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| Speaker system |
| OF THE PREFERRED EMBODIMENT OF THE INVENTION Hereinafter the invention will be described by ... |
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| Elevator control system |
| Accordingly, the primary object of the present invention is to provide an elevator control system ... |
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| Bass reflex type speaker system duct having multiple sound paths |
| The present invention has been designed to prevent leakage of mid frequency sound from the duct to ... |
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| Muffler for an internal combustion engine |
| OF THE PREFERRED EMBODIMENT FIG. 1 depicts a cutaway showing of the muffler of the present ... |
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| Headset with limiter circuit |
| Having thus described our invention what we claim is: 1. A battery-free protective hearing aid ... |
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Electroacoustic transducers comprising vibrating panels
| Details |
Inventors: Davis, Gillian Margaret; Lundie, Thomas; McDonald, Anthony Malcolm;
Assignee: NCT Group, Inc. (Linthicum, MD)
Primary Examiner: Woo; Stella
Assistant Examiner: Ni; Suhan
Attorney, Agent or Firm: Larson; R. Michelle
An electro-acoustic transducer comprises first and second panels (18A,18B) each of which can be vibrated to generate sound, a frame (10) for mounting the panels, and first and second seals (20A,B) arranged between the frame and the edges of the panels for holding the panels in the frame, substantially isolating the frame acoustically from the edges of the panel, and substantially sealing the frame to the edges of the panel. One or more actuators (22), such as piezoelectric elements, are provided for receiving a driving signal and vibrating in response thereto, and the actuators are mechanically and acoustically coupled to the first panel at one or more locations remote from the edges of the first panel so that the first panel vibrates in response to vibration of the actuators. The second panel is mechanically and acoustically coupled to the first panel and/or to the actuators at one or more locations remote from the edges of the second panel so that the second panel also vibrates in response to vibration of the actuator means. The acoustic properties of the panels, the seals, the actuators and the couplings can be chosen to obtain a required frequency response from the transducer. Different embodiments are described in which the panels are driven in phase, in anti-phase, and in a more complex manner. |
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DETAILED DESCRIPTION OF THE INVENTION Referring to FIGS.
1 and 2, the first embodiment of electro-acoustic transducer in the form of a loudspeaker comprises a rectangular frame 10 which is fixed to a rectangular back panel 12 and which are designed to be hung on a wall.
The front edge of the frame 10 has inwardly facing lips 14, and battens 16 are secured around the inside of the frame 10 so that channels 17 are formed between the lips 14 and the battens 16.
The transducer also includes a rectangular vibratable panel 18, the outside dimensions of which are slightly smaller than the inside dimensions of the rectangular frame 10.
A seal 20 is provided around the edge of the vibratable panel 18.
The seal 20 is formed from a length of silicone rubber tubing which has been cut along its length, opened out and clamped around the edges of the panel 18.
The seal 20 is engaged in the channels 17 between the lips 14 and the battens 16, and thus the panel 18 is held in place in the frame 10, with the seal 20 isolating the frame 10 acoustically from the edges of the panel 18 and sealing the frame 10 to the edges of panel 18.
The seal 20 permits very slight movement of the edges of the panel 18 towards and away from the back panel 12, and also permits the edges of the panel 18 to twist slightly in the channels 17 to accommodate multi-modal bending vibration of the panel 18.
An array of six piezoelectric actuators 22 are secured by adhesive 23 to the rear face of the vibratable panel 18.
The actuators 22 are connected together in parallel by wires to a source (not shown) of a high voltage audio driving signal.
In response to the driving signal, the piezoelectric material of the actuators 22 bends at the frequency of the driving signal, thereby causing the panel 18 to vibrate.
The panel 18 vibrates predominantly in a non-pistonic, multi-modal manner by bending, rather than by bodily translation.
This bending is facilitated by the seal 20 between the frame 10 and the edges of the panel 18.
Furthermore, the seal 20 damps out acoustic reflections which may occur at the boundary between the panel 18 and the frame 10 and thus acts as a semi-anechoic termination
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