LOUDSPEAKER ASSEMBLY

Abstract: A loudspeaker assembly for use in electronic devices especially hand held communication devices e.g. a cellular mobile telephone, comprising a loudspeaker (12) for emitting sound through a front cover (9), and a board (8) for mounting components, the board (8) having a first side (10) carrying user interface means (5) accessible through the front plate (9), and a second side (11), facing towards a back cover (7). The loudspeaker (12) is mounted between the board (8) and the back cover (7). Thereby the electronic devices can be made very compact.

Description: Loudspeaker Assembly. This invention relates to a loudspeaker assembly for use m electronic devices, comprising a loudspeaker for emit- ting sound through a front cover, and a board for mounting components, the board having a first side carrying user interface means accessible through the front plate, and a second side facing towards a back cover. On the market for small-sized hand held electronic equip- ment especially mobile telephones, user friendliness is an extremely important parameter m the competition with other vendors of mobile telephones. The development of integrated circuit technology has made it possible to incorporate numerous functions which involve interaction with the user via a user interface. Typically, a user interface comprises relatively large components like a keypad and a display. In different types of electronic equipment, e.g. mobile telephones, a loudspeaker and/or a microphone is also incorporated m the electronic equip- ment. When it is a requirement e.g. that it shall be possible to have access to all functions of the electronic device via a front cover, and that the overall size of the electronic equipment shall be small enough to be held and op- erated by one hand, the overall size of the electronic device constrains the size of the individual components i.e. the keypad, the display, etc. Thereby the display and the keypad get very small and inconvenient to use. From a first type of marketed mobile telephones it is well-known to mount a loudspeaker on the back of a front cover and to connect the loudspeaker to a printed circuit board, PCB, by means of wires. However, this solution is inconvenient m that the speaker occupies much space at the backside of the front cover. This m turn limits the possible maximum size of other components accessible via the front cover. Moreover, such a mobile telephone is rather expensive to manufacture due to the task of mounting the electrical wires . From a second type of marketed mobile telephones it is well-known to mount a loudspeaker on that side of a printed circuit board that faces towards the front cover. However, this solution is also inconvenient m that the speaker occupies much space at the backside of the front cover. Such mobile phones are also rather expensive to manufacture due to the task of mounting, involving soldering, the speaker on the surface of the printed cir- cuit board. Consequently, the prior art involves the problem that the loudspeaker occupies too much space at the backside of the front cover of an electronic device. Thus an object of this invention is to provide a loud- speaker assembly which utilizes the space m electronic devices m a more convenient way. This is achieved when the loudspeaker assembly mentioned m the opening paragraph is characterized m that the loudspeaker is mounted between the board and the back cover. Consequently, the size and the position of other components such as a keypad and a display are not constrained by the loudspeaker. Moreover, the front cover can be made free for electromechanical components. This may facili- tate exchangeable front covers, since it is possible to manufacture cheaper front covers. Further, a designer of an electronic device comprising a loudspeaker assembly according to the invention is allowed to design with a larger degree of freedom. When the board has an opening for transmission of sound, sound is transmitted from the loudspeaker to a lis- tener/user. In an expedient embodiment the loudspeaker assembly comprises a first resonance box including an opening through the front cover and an opening through the board and the first resonance box is otherwise closed. When the loudspeaker assembly comprises a second resonance box which is coupled to the loudspeaker, including an opening through the board, and which is otherwise closed an additional resonance box is created and the high frequency response of the speaker assembly is en- hanced. Consequently, it is possible to reduce the effect of the space surrounding the electronic device, e.g. the ear cavity of a listener, m the reproduction of sound. Further, if the loudspeaker assembly is placed close to a microphone operated m connection with the loudspeaker the resonance boxes may reduce or eliminate undesired acoustical feed-back from the loudspeaker to the microphone . This is possible m particular when the opening through the board connects the first and second resonance boxes. In a particular expedient embodiment the first resonance box has a relatively small cross sectional area m a plane substantially parallel to the board compared to the cross sectional area, m a plane substantially parallel to the board, of the second resonance box. Thereby sound is transferred from the loudspeaker to the listener via two resonance boxes which can be designed for a specific sound transmission, while very little space is occupied on the back side of the front cover. This is also possible when the first resonance box has a relatively small cross sectional area m a plane substan- tially parallel to the board compared to the diameter of the louαspeaker. The loudspeaker may be attached to the second side of the board to form a resonance box between the board and the loudspeaker. Thereby only a minimum of effort is needed m mounting the speaker when high-volume production of electronic devices is considered. Alternatively, the loudspeaker may be attached to the inner side of the back plate, the inner side facing towards the second side of the board. Hereby, it is possible to mount the speaker on the back cover independently of the process of mounting other components on the printed circuit board. In an expedient embodiment a first side of the loudspeaker is coupled to the second resonance box and a sec- ond side of the loudspeaker is coupled to another volume by means of a sound channel. Thereby an additional design parameter is included. When the loudspeaker is connected to the board by means of electrical connectors extending within the second resonance box a very compact and cost-effective solution for high-volume production is obtained. Moreover, the invention relates to a mobile telephone comprising a loudspeaker assembly. Brief Description of the Drawings The invention will be explained more fully below m con ¬ nection with a preferred embodiment and with reference to the drawing, m which: fig. 1 shows a prior art embodiment of a loudspeaker as- sembly, fig. 2 shows a first preferred embodiment of the inven ¬ tion, and fig. 3 shows a second preferred embodiment of the inven ¬ tion. Detailed Description of a Preferred Embodiment Typically, an electronic device such as a mobile telephone comprises a front cover and a back cover forming a housing for different types of electrical and electromechanical components. In the following the volume enclosed by the housing is denoted the 'interior' and the volume not enclosed by the housing is denoted the 'surround¬ Fig. 1 shows a cross-sectional view through a prior art embodiment of a loudspeaker assembly m an electronic de- vice. In this embodiment a loudspeaker 3 is mounted on the back side of a front cover 2 having an opening 6 for transmission of sound from the loudspeaker 3 to the surroundings. The loudspeaker is electrically connected to a printed circuit board 1 by means of a wire 4. The means 5 is adapted for operating the electronic device e.g. a mobile telephone. Such means can be e.g. a display or a keypad. The electronic device is designed such that a user/listener can hold the electronic device m his hand and with the front cover against his cheek while the opening 6 is opposite to the user's ear 19. However, the means 5 is limited m size due to the loudspeaker occupying space immediately next to the means 5. Fig. 2 shows a cross-sectional view through a first preferred embodiment of the invention. In this embodiment the loudspeaker 12 is mounted on the inner side of a back cover 7. The loudspeaker 12 is connected electrically to a printed circuit board 8 by means of connectors 13. In a preferred embodiment the connectors 13 are e.g. surface mounted pogo pins which establish contact with the speaker by pressing against contact pads (not shown) on the speaker 12. The printed circuit board 8 has an opening 15 for transmission of sound from the speaker 12 to the surroundings via the opening 15 m the printed circuit board and the opening 14 m the front cover 9. In a preferred embodiment the aperture of the opening 15 is larger than the aperture of the opening 14. Thereby the intensity of the sound generated by the loudspeaker is transferred to the surroundings with only a relatively small loss of intensity. In this embodiment the speaker does not occupy space on the back side of the front cover 9, and it is thus possible to use larger means 5 (e.g. a display or a keypad) for operating the electronic device or to move the means 5 closer to the opening 14. Fig. 3 shows a cross-sectional view through a second preferred embodiment of the invention. This embodiment differs from the embodiment shown m fig. 2 m that the loudspeaker assembly further comprises two gaskets 16 and 17 enclosing a first resonance box and a second resonance box, respectively. Further, the loudspeaker 12 is coupled to a sound channel allowing for passage of sound generated by the loudspeaker. This is illustrated with the ar- row 18. In practice, the type of speaker dictates whether this sound channel is needed or not. The first resonance box, enclosed by the gasket 16, causes an additional resonance frequency to occur in the sound pressure versus frequency diagram for the loudspeaker assembly. This provides the acoustic engineer dimensioning the loudspeaker assembly with more degrees of freedom. Essentially, it becomes easier to provide a relatively high sound pressure (about 2-5 dB) at higher frequencies (about 1500 Hz - 3KHz) . Further, due to the fact that sound pressure and the characteristics of the sound transmitted to the surround ¬ ings are substantially determined by the first and second resonance boxes, the surroundings (e.g. a listener's ear cavity) only play a minor role in the reproduction of sound. Thereby, only minor constraints regarding the de ¬ sign of the front cover should be fulfilled in order to obtain a good reproduction of sound. Further, the designer is allowed to put more focus on man-machine- interface aspects. In a preferred embodiment the gaskets 16 and 17 have a cylindrical shape. The gaskets can be made of rubber, a plastic material, or another suitable material. The openings 14 and 15 can be supplied with some type of acoustic valve e.g. in the form of a wool-like material. The interior of the first and second resonance boxes may be filled or partly filled with some type of material expedient for enhancing the reproduction of sound. The loudspeaker can be of different types comprising e.g. electromagnetic types, piezo-electric types, or electro ¬ static types. Although preferred embodiments of the method and apparatus of the present invention have been illustrated in the accompanying drawings and described in the foregoing detailed description, it is understood that the invention is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications, and substitutions without departing from the spirit of the invention as set forth by the following claims.

Claims: CLAIMS 1. A loudspeaker assembly for use in electronic devices, comprising a loudspeaker (12) for emitting sound through a front cover ( 9) , and a board (8) for mounting components, the board having a first side (10) carrying user interface means (5) accessible through the front plate (9), and a second side (11) facing towards a back cover (17), characterized in that the loudspeaker (12) is mounted between the board (8) and the back cover (7) . 2. A loudspeaker assembly according to claim 1, characterized in that the board (8) has an opening (15) for transmission of sound. 3. A loudspeaker assembly according to claim 2, characterized in that the loudspeaker assembly comprises a first resonance box including an opening (14) through the front cover (9) and an opening (15) through the board, and that the first resonance box is otherwise closed. 4. A loudspeaker assembly according to claim 1-3, characterized in that the loudspeaker assembly comprises a sec- ond resonance box coupled to the loudspeaker (12), including an opening (15) through the board (8), and which is otherwise closed. 5. A loudspeaker assembly according to claim 4, characterized m that the opening (15) through the board (8) connects the first and second resonance boxes. 6. A loudspeaker assembly according to claims 3-5, char- acterized m that the first resonance box has a relatively small cross sectional area m a plane substantially parallel to the board (8) compared to the cross sectional area, m a plane substantially parallel to the board (8), of the second resonance box. 7. A loudspeaker assembly according to claims 1-6, characterized m that the first resonance box has a relatively small cross sectional area in a plane substantial parallel to the board (8) compared to the diameter of the loudspeaker (12) . 8. A loudspeaker assembly according to claims 1-7, characterized m that the loudspeaker is attached to the second side (11) of the board (8) to form a resonance box between the board (8) and the loudspeaker (12) . 9. A loudspeaker assembly according to claims 1-8, char- acterized m that the loudspeaker (12) is attached to the inner side of the back cover (7), the inner side facing towards the second side (11) of the board (8) . 10. A loudspeaker assembly according to claims 4-9, characterized m that a first side of the loudspeaker (12) is coupled to the second resonance box and that a second side of the loudspeaker is coupled to another volume by means of a sound channel. 11. A loudspeaker assembly according to claims 4-10, characterized m that the loudspeaker (12) is connected to the board (8) by means of electrical connectors (13) extending within the second resonance box. 2. A mobile telephone comprising a loudspeaker assembly s set forth in any of the claims 1-11.

Inventors: LARSSON MATS, LARSSON PAUL, MOESTER ERIK, OLSSON MATS, PORTELA RAFAEL, SIMONSSON OLOF, LARSSON, MATS, LARSSON, PAUL, MOESTER, ERIK, OLSSON, MATS, PORTELA, RAFAEL, SIMONSSON, OLOF
Applicants: ERICSSON TELEFON AB L M, TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)
Application year: 2000
Main classification: H04R1
IPC codes: H04M1, H04R1