Abstract:
The present disclosure describes a receptacle for acoustically guiding tones emitted from the side of the transducer. The receptacle is adapted to be mounted onto an acoustic transducer within a housing for acoustically sealing and guiding sound from the transducer. The receptacle has a depression on the bottom surface adapted for mating with and sealing the acoustic transducer.

Description:
TECHNICAL FIELD 
     The present specification generally relates to communication devices. More particularly, the present specification describes an acoustic guide for audio transducers. 
     BACKGROUND 
     Communication devices are presently being extensively utilized in a wide range of applications. Communication devices typically include a ringer enabling a user to receive audible notification of incoming calls. Manufacturing the communication device requires a way of acoustically coupling the transducer to the housing. 
     Audio transducers for generating audio tones are used as ringers in a cellular telephone. The ring tone needs to be loud enough to be heard. However, government regulations prohibit the ring tone from going towards the user&#39;s ear. Unfortunately, typical audio transducers for mounting on printed circuit boards emit their maximum audio levels in a direction perpendicular to the printed circuit board. The sound emitted from the transducer reflects off the inner surface of the housing enclosing the circuit board and bounces around inside the housing. As a result, the sound coming out of an audio port opening in the housing is often muffled and attenuated. 
     SUMMARY 
     The inventor noticed that to improve the ringing efficiency of a communication device, it is advantageous to provide an acoustic guide between a printed circuit board mounted audio transducer and an audio port opening on the side of the telephone housing. Ringing tones are emitted from the side of the transducer. The tones are acoustically guided through a resonant cavity formed by a hole on the side of the acoustic guide and an opening on the side of the transducer. 
     The present disclosure describes a receptacle for acoustically guiding tones emitted from the side of the transducer. The receptacle is mounted onto an acoustic transducer within a housing for acoustically sealing and guiding sound from the transducer. The receptacle has a depression on the bottom surface adapted for mating with and sealing the acoustic transducer. In a preferred embodiment, the sidewalls of the depression are inclined at approximately one degree. 
     An acoustic waveguide is formed by a resonant cavity on one side of the receptacle. The resonant cavity abuts an opening of the transducer on one side and an audio port opening of the housing on the other. In a further preferred embodiment, the physical volume of the resonant cavity is optimized to match the acoustic wave impedance with the operating frequency of the acoustic transducer. The acoustic waveguide formed by the resonant cavity diverts sound from the acoustic transducer at approximately 90 degrees from the perpendicular. 
     A plurality of standoff features is. formed on top of the receptacle. The plurality of standoff features provide optimum compression to the receptacle such that compression provides acoustic and weatherproof seal as well as shock and vibration absorption for the transducer. In another preferred embodiment, the plurality of standoff features has different heights to accommodate the curvature of the housing. In a particular embodiment, there are four standoff features. 
     In a further particular embodiment, the receptacle includes a tab formed on a side of the receptacle. The tab is used for easy removal of the receptacle from the transducer. The receptacle is molded as one piece of elastomeric material. 
     The present disclosure also describes a phone handset. The handset includes a housing, a printed circuit board, an acoustic transducer, and a receptacle as described above. 
     The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other embodiments and advantages will become apparent from the following description and drawings, and from the claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is a top view of cellular telephone housing. 
     FIG. 1B is a side view of cellular telephone housing. 
     FIG. 2A is a cross-sectional view of the housing showing a transducer mounted on top of a printed circuit board. 
     FIG. 2B is another cross-sectional view of the housing showing a receptacle fitted on top of the transducer. 
     FIG. 3A is an exploded perspective view of the telephone handset with the receptacle separate from the transducer. 
     FIG. 3B is an exploded perspective view of the telephone handset showing the receptacle mounted on top of the transducer. 
     FIG. 4A is a top perspective view of the receptacle. 
     FIG. 4B is a bottom perspective view of the receptacle. 
     FIG. 4C is a cross-sectional view of the receptacle. 
     Like reference numbers and designations in the various drawings indicate like elements. 
    
    
     DETAILED DESCRIPTION 
     A receptacle  202  for mounting a ringer alert transducer  200  within a housing  100  is disclosed. The receptacle  202  is molded from a flexible material providing an acoustic seal between the transducer  200  and housing  100 . FIGS. 1A and 1B show the top and side view respectively of cellular telephone housing. 
     The standoff features  204  are nipple-shaped devices that are formed on top of the molded receptacle  202 . When the housing  100  presses down on the standoff features  204 , the standoff features  204  apply sufficient force to compress the flexible molded receptacle  202  around the ringer alert transducer  200  so that the inside surfaces  205  of the receptacle  202  are pressed against, or loosely fit around, the outside surfaces  201  of the transducer. The inner dimension of the element is preferably about {fraction (4/1000)} inch smaller than the outside of the transducer. Each of the four standoff features  204  has a different height to accommodate the curvature of inside surface  203  of the housing  100 . The optimum compression applied provides acoustic and weatherproof seal for the transducer  200 . The acoustic seal minimizes muffling of the sound. The weatherproof seal can prevent the water from dispersing throughout the housing. 
     The standoff features  204  also provide shock and vibration absorption to prevent audible distortion and gradual degradation of the transducer performance. 
     FIG. 2A shows a cross-sectional view of the housing with a printed circuit board  206  and the transducer  200 . FIG. 2B is another cross-sectional view of the housing with the flexible receptacle  202  mounted on top of the transducer  200 . The cavity  209  is shown leading the sound to an edge of the telephone. 
     The receptacle  202  has a hole  302  on one side to guide the sound from the transducer  200  to the audio port opening  208  on the side of the housing  100 . The hole  302  is aligned with an opening  304  on the side of the transducer  200  thereby providing an electroacoustic interface. The side of the flexible receptacle  202  with the hole  302  also abuts the interior surface of the housing  100  at the audio port opening  208 . 
     FIG. 3A shows an exploded perspective view of the telephone handset  300  with the flexible receptacle  202  separate from the transducer  200 . FIG. 3B shows the flexible receptacle  202  fitted on top of the transducer  200 . The flexible receptacle  202  provides acoustic seal and guide for the tones generated by the transducer  200 . A speaker  306  produces certain sounds that are carried to the user&#39;s ear through openings  208  on the housing  300 . 
     FIGS. 4A and 4B show top and bottom perspective views respectively of the flexible receptacle  202 . The hole  302  in the flexible receptacle  202  and the opening  304  on the side of the transducer  200  preferably forms a resonant cavity  400 . The cavity  400  acts as an acoustic waveguide that diverts sound at approximately a 90-degree angle with low loss and good acoustic isolation. The volume of the resonant cavity  400  is optimized to match the acoustic wave impedance with an operating frequency of the ringer alert transducer  200 . The volume can also be chosen to optimize the sound pressure level output. A tab  406  is also formed on one side of the flexible receptacle  202  to facilitate removal of the receptacle  202  from the transducer  200 . 
     A cross-sectional view of the flexible receptacle in FIG. 4C shows the depression  402  formed on the bottom side formed from the inner surfaces  205 . The depression  402  fits snugly over the transducer  200  and provides easy alignment and seal. Sidewalls of the depression  402  are slightly inclined. In a preferred embodiment, the inclination angle, θ, is approximately one degree. 
     Advantages of the flexible receptacle  202  include low cost and simple fabrication process. The receptacle  202  is molded as one piece of resilient material. The snug fit of the depression  402  over the transducer  200  provides easy alignment and seal for low cost assembly of cellular phones. The design of the resonant cavity  400  with an opening directed to the side of the housing at approximately 90 degrees from the perpendicular improves the ringer volume while directing sound away from earpiece for hearing safety. The top walls of the receptacle can have a uniform thickness. The standoff features allow the receptacle to abut against any shaped inner surface, e.g. an irregular shaped inner surface as shown in FIG.  2 B. 
     A number of embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.