AU618479B2 - A dual speaker - Google Patents

Description

S F Ref: 122957 FORM COMMONWEALTH OF AUS- <LIA PATENTS ACT 195; COMPLETE SPECIFICATION 4f 4

(ORIGINAL)

FOR OFFICE USE: Class Int. Class Application Number: PJ4203 4 14 @04 4 44 4 4 o 44.

0 44 I 4 44$ 4 Lodged: 16 May 1989 Accepted: Published: Priority: Related Art: i

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Name and Address of Applicant: Actual Inventor: Address for Service: Exicom Australia Pty Limited 554 Parramatta Road Ashfield New South Wales 2131

AUSTRALIA

NOT KNOWN Spruson Ferguson, Patent Attorneys, Level 33 St Martins Tower, 31 Market Street, Sydney, New South Wales, 2000, Australia Complete Specification for the invention entitled: A Dual Speaker The following statement is a full description of this invention, including the best method of peiforming it known to me/us REPRINT OF RECEIP'T 1-A-,7 1, 4/ o TA 5815/2 O 1) O L s*I) O1 00

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L* I t t ii -2- The present invention concerns acoustic output transducers such as are commonly known as "loud speakers", and is particularly concerned with the problems associated with the provision of two limited frequency response acoustic output transducers in a single piece of equipment where they are positioned in a limited space.

A typical example of this problem occurs in a loud speaking telephone, where a ringer and a speech transducer are both housed in the same instrument. The ringer transducer is used to transmit the ringing tones and the speech transducer is used to transmit received speech (and possibly also to act as a microphone). In the past in such instruments two separate transducers having different frequency responses, and being connected to separate and isolated circuits, have been employed. This has tended to increase the size of the instrument and to increase its complexity and expense.

15 According to a first aspect of the present invention there is disclosed a dual loudspeaker arrangement comprising first and second transducers and.three acoustic cavities, one of said cavities being formed bcuocc',es \c\urg withAboth said transducers and each of the second and third cavities being formed with~onlyone of said first transducer and said second transducer respectively. In a preferred arrangement, the aperture(s) serve to match the impedance of the transducer of the respective cavity to that of free air and also serve to damp the acoustic output of the transducer of the respective cavity to provide the desired frequency response of that transducer.

25 Preferably the transducers are ceramic acoustic transducers, and advantageously both the transducers are identical.

Also preferably the transducers are substantially planar and mounted parallel to each other one above the other. In this way the first resonant cavity is defined between the transducers, and the second and third resonant cavities are defined above the upper transducer and below the second transducer respectively.

In many applications it will be of advantage that the transducers are provided with different frequency responses, and in a preferred embodiment one transducer is the ringtone transducer and the other is the speech transducer of a telephone.

According to a second aspect of the present invention there is provided a telephone instrument equipped with a dual speaker as hereinbefore 4] I -3- ;a; t

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A'q ''4 defined in which the first acoustic output transducer is a ringtone transducer and the second acoustic output transducer is a speech transducer.

A preferred embodiment of the present invention will now be described with reference to the accompanying drawings, in which: Fig. 1 is a plan view of a dual speaker; Fig. 2 is a sectional elevation of the dual speaker of Fig. 1; and Fig. 3 is a view from beneath the speaker of Fig. 1.

Referring now to the drawings, dual speaker 1 appears as a squat cylinder made from an upper casing 2 and lower casing 3 interconnected by snap attachment to an annular member 4. A first acoustic output transducer 5 is mounted inside the upper casing 2 and held in position by one end of 0 the annular member 4. A second acoustic output transducer 6 is mounted in S the lower casing 3 and held in position by the other end of the annular ,lob member 4. Electrical leads 7 and 8 extend from the first and second transducers to their respective associated circuitry 9 and 10, indicated S generally.

The position of the two transducers within the dual speaker defines a first, cylindrical resonant cavity 11 bounded at its upper and lower ends 20 by the transducers 5 and 6, and bounded around its sides by the annular member 4. A second resonant cavity 12 is defined between the transducer 00 0o and upper casing member 2, and this cavity communicates with the free air Sby virtue of an aperture 13 in the casing member 2.

"A third resonant cavity 14 is defined between the transducer 6 and lower casing member 3, and this cavity communicates with the free air by means of two apertures 15 and 16 in the lower casing member 3. The aperture 15 Is considerably larger than the aperture 16.

the The impedance of transducer 5 is matched to that of the free air, and the damping ne.cessary for the required frequency response is performed by the first cavity 11, the second cavity 12 and aperture 13.

Similarly the impedance transformation to match the Impedance of the transducer 6 to the free air and the damping necessary for its frequency response are performed by the first cavity 11, third cavity 14 and apertures 15 and 16.

The aperture 13 provides a high amount of damping and Improves the lower frequency performance of speech transducer 5 to a surprising extent.

The aperture 15 is tuned to the ringtone fundamental frequency, whereas aperture 16 is tuned to the third harmonic of the rlngtone.

IAD/9370 -4- In this way required frequency responses are available for the transducers to develop their desired acoustic efficiency.

It should be appreciated that although the invention has been described with reference to a specific example it may be configured in many other ways, for instance the transducers need not be parallel to each other. It should also be appreciated that there are many other uses to which such a dual speaker can be put besides use in a telephone instrument.

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IAD/9370

Claims (11)

1. A dual loudspeaker arrangement comprising first and second transducers and three acoustic cavities, one of said cavities being formed withAboth said transducers and each of the second and third cavities being formed withlonly one of said first transducer and said second transducer respectively.

2. An arrangement as claimed in claim 1 wherein said first and second transducers define corresponding boundaries of said one cavity.

3. An arrangement as claimed in claim 2 wherein said first and second transducers form opposite boundaries of said one cavity.

4. An arrangement as claimed in any one of claims 1 to 3 wherein said first transducer forms a boundary of said second cavity. An arrangement as claimed in any one of claims 1 to 4 wherein said second transducer forms a boundary of said third cavity.

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6. An arrangement as claimed in any one of the preceding claims wherein boundaries of said second and third cavities each include at least one aperture.

7. An arrangement as claimed in claim 6 wherein said aperture(s) i serve to match the impedance of the transducer of the respective cavity to that of free air and also serve to damp the acoustic output of the transducer of the respective cavity to provide the desired frequency response of that transducer.

8. An arrangement as claimed in any one of the preceding claims I wherein said transducers are substantially identical ceramic acoustic transducers, are substantially planar, and are mounted in substantially parallel planes. 0:

9. A telephone handset including a dual loudspeaker arrangement as claimed in any one of the preceding claims.

A telephone handset as claimed in claim 8 wherein the first transducer is a ringtone transducer and the second transducer is a speech transducer.

11. A dual loudspeaker arrangement substantially as described herein'with reference to the drawings. DATED this TNENTY-THIRD day of SEPTEMBER 1991 Exicom Australia Pty Limited Patent Attorneys for the Applicant SPRUSON FERGUSON IAD/937o