Abstract:
A speaker module for a personal communication device includes two transducers for generating sound on the basis of an electrical signal. One transducer outputs sound to the surroundings from a sound output thereof and the other transducer outputs sound to the surroundings via the first transducer. In this manner, two transducers require only one sound output. The sound from the second transducer may be transmitted through and filtered by an opening in a diaphragm of the first transducer. Filtering elements may be provided between the two transducers.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of the U.S. Provisional Application 60/840,585, filed on Aug. 28, 2006, entitled “Multiple Receivers With A Common Spout” and is hereby incorporated by reference in its entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to a system comprising two transducers/receivers for outputting sound from a single output, and in particular to a system where one transducer outputs sound via the other transducer.  
       BACKGROUND OF THE INVENTION  
       [0003]     In today&#39;s In Ear Monitors (IEMs) and similar devices for Personal Use (Personal Monitors), very often more than one receiver is used to obtain the required performance in terms of frequency range extension and maximum sound pressure capability. One example of such a multiple receiver or speaker IEMs is disclosed in US Published Patent Application 2006/0133636, titled “Sound Tube Tuned Multi-Driver Earpiece.” In such receivers/speakers, it is required to connect the separate sound outlets or spouts of each receiver to respective appropriately dimensioned sound tubes or sound conducting members in an acoustically sealed manner. The 3300 series receiver manufactured and sold by Sonion Nederland B.V comprises two back-to-back mounted moving armature receivers with separate sound ports emitting respective sound signals into a common spout. Both of these solutions put requirements to the space required by and the acoustical properties of this acoustical coupling.  
       SUMMARY OF THE INVENTION  
       [0004]     One object of this invention is to provide a speaker module or assembly that simplifies the mounting and sealing of a multiple receiver output. A significant advantage of the present loudspeaker module is the potential reduction of the space occupied by the sound tubes and/or sound conducting members, which is particularly important in hearing prostheses and IEMs that must fit inside the ear canal or outer ear of the user.  
         [0005]     In a first aspect, the invention relates to a speaker module for use in a personal communication device, the module comprising a first transducer and a second transducer. The first transducer is adapted to receive a first electrical signal and output a corresponding sound and comprises a first housing, a movable diaphragm positioned inside the first housing and which divides an inner space of the first housing into a first chamber and a second chamber, a sound output port connecting one or both of the first chamber and the second chamber to the surroundings, and a sound input connected to the first or the second chamber. The second transducer is adapted to receive a second electrical signal and output a corresponding sound and comprises a second housing, a movable diaphragm positioned within the second housing and which divides an inner space of the second housing into a third chamber and a fourth chamber, and a sound output connected to one or both of the third chamber and the fourth chamber, the second sound output being acoustically connected to the sound input of the first transducer.  
         [0006]     In the present context, a personal communication device is a device which may be portable and battery operated and which is used for providing sound for the person. Such a device may be a headset, a hearing aid, an in-ear monitor, a hearing protection device, a cell-phone, a PDA, or the like.  
         [0007]     Sound or audible sound normally is defined as having a frequency of between 20 Hz and 20 kHz, even though wider or narrower intervals may be used in certain situations.  
         [0008]     Preferably, in the first housing, the sound inlet is positioned at a first location and the sound outlet in a different location so that the sound output of the second transducer propagates from the second housing to the surroundings via the first and/or second chambers of the first housing. Then, when both transducers/receivers are active, the output of the assembly is the sum of the output of the first receiver/transducer and that of the second receiver/transducer as affected by the transport through the first receiver/transducer.  
         [0009]     The present speaker module need not be assembled to a single module. The individual transducers may initially be separate to be fixed to each other at a later point in time, or they may be acoustically assembled (in order to have the sound output of the second transducer acoustically connected to the sound input of the first transducer) in a manner where these transducers are not fixed to each other or a common member.  
         [0010]     In fact, as will also be described further below, an element may be provided for guiding sound from the sound output of the second transducer to the sound input of the first transducer, so that these transducers need not abut or be fixed in relation to each other.  
         [0011]     In this context, the housings each define an inner space in which the diaphragm is positioned. In order for the diaphragm to provide a suitable sound pressure, the diaphragm should divide the inner space into two chambers, normally called the front and back chamber, where the sound output may be from any of these chambers. Smaller venting openings may be provided in the housing and/or diaphragm in order to provide static pressure relief. In addition vent opening(s) in the housing may be used to increase the volume of one or more chambers of the first and second transducers to, for example, increase the low frequency output level. In some instances, the vent openings may advantageously be utilized to form a Helmholtz resonator with a resonance frequency between, for example, 60 Hz and 200 Hz. In fact, two or more vents may be acoustically connected to any chamber in order to adapt or tailor the frequency response of the transducer in question to any desired shape. Thus, when providing a tuned venting or any other opening from a chamber to the surroundings, no additional opening is required to handle the static pressure relief.  
         [0012]     The present “connecting” of the input or output to the surroundings will be an acoustic connection where sound is propagated between the chamber in question and the surroundings. It is noted that this connection may be obtained via a flexible element or via an opening. In addition to providing a sound or acoustical connection, this element or opening may also provide a frequency dependent filtering of the sound. This is usual and is taken into account when defining the transducer and its sound output characteristics.  
         [0013]     In the present context, the transducers receive an electrical signal and provide a corresponding sound. Naturally, many forms of correspondence may be seen in that even in macroscopic loudspeakers, different loudspeakers have different sounds when playing the same music. This is accepted, and the sound desired or required is a matter of personal taste or of the requirements of the listener. Thus, the sound output of a hearing aid in the ear of a hearing impaired person may be strongly filtered to emphasize certain frequency intervals, but this is required in order to have the person hear the sound in a more natural or neutral manner due to the person&#39;s hearing impairedness. This desired sound may be generated by altering the electrical signal and/or the acoustical elements or characteristics of the transducer. Either way, this will also be seen as a sound corresponding to the electrical signal.  
         [0014]     Naturally, any type of electro-acoustical transducer may be used in loudspeaker modules according to the present invention, such as, but not limited to, Balanced Armature Receivers, Moving Coil receivers, piezoelectric receivers, etcetera, or any combination thereof.  
         [0015]     The second transducer preferably has no other sound outputs, and outputs its sound via the sound inlet and first/second chamber(s) of the first transducer.  
         [0016]     Clearly, in addition to the limitation of the number of sound output ports to the surroundings, the invention also provides numerous additional manners of filtering the sound from the second transducer. Naturally, both the acoustical properties of the sound inlet of the first transducer as well as the acoustical properties of the first transducer will affect the sound received from the second transducer before outputting this sound.  
         [0017]     In one embodiment, the sound output port of the first transducer is connected to the first chamber, and the sound input of the first transducer is connected to the second chamber. Thus, in this embodiment, sound from the second transducer is transmitted to the surroundings via also the diaphragm of the first transducer.  
         [0018]     In that embodiment, the diaphragm of the first transducer or the diaphragm suspension may comprise a hole or opening of predetermined shape and dimensions. This opening will then also affect the sound of the second transducer, since sound is propagated through the hole or opening in order to exit the first transducer. This opening may have dimensions sufficiently large to provide a frequency selective filtering of the sound passing through the diaphragm. The larger the opening or hole is, the lower will be the attenuation of especially higher frequencies when passing this opening/hole.  
         [0019]     In general, the first transducer may have a first acoustic resonance frequency and the second transducer may have a second acoustic resonance frequency, the second resonance frequency being lower than the first resonance frequency, where the opening or hole in the diaphragm of the first transducer then is adapted to transmit sound at the second resonance frequency.  
         [0020]     In this situation, the resonance frequency is that of moving parts in the transducer, normally the diaphragm and movable parts of the driving means driving the diaphragm. Normally, the higher the resonance frequency, the higher a sound frequency spectrum is the transducer used for emitting or radiating. Thus, a tweeter normally has a higher resonance frequency than a mid-range transducer or a woofer. Naturally, the two transducers may have substantially the same resonance frequency. Then, if the transducers have different impedances, the lower impedance transducer may be used as a tweeter, by coupling through a capacitor, and the other transducer may be used as a woofer.  
         [0021]     Of course, the transducers may have different sizes. Normally, the larger housing will have the lower acoustical resonance frequency.  
         [0022]     Naturally, the frequency response of a transducer need not be fully defined by the resonance frequency. A tweeter having a resonance frequency of 2-5 kHz normally will be able to output up to 20 kHz, and a woofer having a resonance frequency as low as possible (e.g. about 500-1500 Hz) may output sound below 20-50 Hz.  
         [0023]     Then, the opening in the diaphragm/suspension will be able to transmit the sound to at least a significant degree. In this context, “transmit” will mean attenuate at most about 1 dB or 3 dB. For example, an opening of 50-300 μm will transmit frequencies of up to about 40 Hz with virtually no attenuation. Sound at 500 Hz, for example, may, in contrast, be attenuated more than 20 dB.  
         [0024]     Thus, the second transducer may be used as a woofer transmitting the lower frequencies of the overall sound into the first transducer, through the opening/hole in the diaphragm/suspension and out via the output port of the first transducer, which then may be used as a tweeter.  
         [0025]     In another embodiment, the module comprises a sound filtering means adapted to guide sound from the sound output of the second transducer to the sound input of the first transducer, the sound filtering means having dimensions providing a filtering of the guided sound. The sound filtering means may be used for attaching the first and second transducers to each other or fixing them in relation to each other. The sound filtering means also provides more degrees of freedom as to the positioning of the sound inlet and the sound output of the second transducer in relation to each other. Omission of any means therebetween will normally require the sound inlet and the sound output to abut each other in order to have sound pass from the second transducer to the first transducer.  
         [0026]     The sound filtering means may comprise a sound guiding channel provided between the first and second transducers and being at least partly defined by outer surfaces of the first and/or second transducers.  
         [0027]     In this manner, the sound filtering means may simply be provided as an element having therein an open channel, which is closed upon contact with the outer surface(s) of the first and/or second transducer(s).  
         [0028]     Optionally or additionally, in this embodiment, the sound filtering means may be at least partly defined by a separate means provided between the first and second transducers.  
         [0029]     In an interesting embodiment, the sound filtering means primarily extends in a plane at least substantially parallel to an outer surface of the first and/or the second transducer. This provides a filtering means of any desired shape and length which nevertheless requires little space.  
         [0030]     An interesting aspect of this embodiment is one wherein the filtering means is actually provided in a wall part of the housing of one of the first and second transducers. In this manner, the filtering means actually are provided as a channel provided inside the wall, and the opening toward the surroundings then is an opening into the filtering means.  
         [0031]     In another embodiment, one of the first and second transducers comprises means for receiving an electrical signal, a filtering circuit positioned within the one transducer and being adapted to receive the electrical signal and provide two electrical signals, and means for outputting one of the provided electrical signals from the one transducer to the other of the first and second transducer.  
         [0032]     Thus, the filtering circuit is provided inside one of the transducers, whereby the other transducer may have a standard input with, for example, only two conductors, at least one of which may be connected to the output of the one transducer.  
         [0033]     Especially if the one transducer is the first transducer, having the sound inlet, the second transducer may be an off-the-shelf transducer. However, the sound output of the second transducer may be chosen in alternative positions now determined by the acoustical connection desired between the first and second transducers.  
         [0034]     In this embodiment, the receiving means of the one transducer comprises at least two electrical terminals or connections between the inner space of the one transducer and the surroundings, and the outputting means comprises at least one further electrical terminal or connection between the inner space of the one transducer and the surroundings.  
         [0035]     A third aspect of the invention relates to a method of operating the above module, the method comprising providing an electrical signal to the second transducer, the second transducer outputting a sound through the sound output thereof into the sound input and first or second chamber of the first transducer, and subsequently to the surroundings via the sound output port of the first transducer.  
         [0036]     Thus, in general, the transducers of the module may have the same size or different size or shape (e.g. cylindrical, D-shaped, rectangular). In certain applications it could be better to have the sound coming out of the ‘tweeter’ (preferred to get the best high frequency response). In others it could be preferred to have the sound coming out of the “woofer”. This depends on, for instance, the interaction between the two receivers in the frequency domain and the time domain. Sometimes phase shifts between the receivers cannot be corrected electronically, but might be corrected by the position of the holes in the cover and where the sound leaves the module. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0037]     The foregoing and other advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings.  
         [0038]      FIG. 1  illustrates a cross section of a system comprising two transducers and a single sound output to the surroundings.  
         [0039]      FIG. 2  illustrates a cross section of a system where sound from one transducer is guided past the diaphragm of the other transducer.  
         [0040]      FIG. 3  illustrates a cross section of a system having a damping element between the two transducers.  
         [0041]      FIG. 4  illustrates the use of a separate element for guiding sound from one transducer to the other transducer.  
         [0042]      FIG. 5  illustrates an alternative shape of a sound guiding element.  
         [0043]      FIG. 6  illustrates a crossover network for use in the present system. 
     
    
       [0044]     While the invention is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, alternatives, combinations and/or sub-combinations of the disclosed concepts falling within the spirit and scope of the disclosed invention as defined, herein and as set forth in the appended claims.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0045]     In  FIG. 1 , an embodiment is seen wherein two transducers,  10 ,  20 , are provided. The first transducer  10  has a movable diaphragm  12  adapted to be moved so as to generate sound. Suitable motor or movement generating means used therefore are well known. Such motor means are positioned within the housing of transducer  10  and are fed an electrical signal via solder bumps  18  outside the housing.  
         [0046]     The diaphragm  12  separates an inner space of the transducer  10  into a first chamber  14  and a second chamber  16 . These chambers normally are called the upper chamber and the lower chamber of the transducer  10 .  
         [0047]     One of the chambers  14 ,  16  is connected to a sound output  11  adapted to guide sound from inside the transducer  10  to the surroundings. This sound output  11  preferably has a spout connected thereto in order to facilitate acoustical connection thereto.  
         [0048]     So far, the transducer  10  may be a standard receiver as is well known in the field of hearing aids, headsets, personal communication devices, in-ear monitors, hearing protection devices, cell phones, PDA&#39;s and the like, where highly efficient and extremely compact sound emitters are required.  
         [0049]     The second transducer  20  also has a number of standard elements: a movable diaphragm  22  dividing the inner space of the transducer  20  into a third chamber  24  and a fourth chamber  26 , solder bumps  28  for use in feeding an internal motor/movement means engaging the diaphragm  22 , as well as a sound output  21 .  
         [0050]     However, the first transducer  10  also comprises a sound inlet  19 , and the transducer  20  is positioned so as to output sound from the output  21  into the inlet  19 . Thus, the sound from transducer  20  is output to the surroundings via one of the chambers  14 / 16  and the sound output  11  of the transducer  10 .  
         [0051]     In this manner, only a single output  11  is provided from the two transducers.  
         [0052]     Naturally, the inlet  19  and the output  11  may be from the same or different chambers ( 14  and  16 ).  
         [0053]     It may be desired to provide a resilient damping material between the transducers  10 ,  20  in order to avoid rub and buzz noise from these when vibrating.  
         [0054]     In addition, the transducers  10 ,  20  may be identical or different. The difference may be in size/shape, frequency output (e.g., tweeter/midrange/woofer), intensity output, driver type (e.g., Moving Coil, Balanced Armature, Piezo), or the like.  
         [0055]     As will become clear further below, this manner of outputting the sound from transducer  20  via the transducer  10  provides a large number of filtering possibilities, whereby the sound from the two transducers  10 ,  20  may be filtered in a number of manners. The sound from the transducer  10  is affected both by the inlet  19  and the transducer  20  (chambers  24 / 26 , diaphragm  22 ) as well as the output  11 .  
         [0056]     Different characteristics will be seen depending of whether the inlet  19  is in the same or the other chamber ( 14 ,  16 ) as the output  11 .  
         [0057]     Also, the positions of the output  21  and inlet  19  in the respective transducers  10 ,  20  will have an effect on the sound output from the output  11 .  
         [0058]     The sound from the transducer  20  naturally is affected by the output  21 , inlet  19  as well as the internal components of the first transducer  10 .  
         [0059]     In addition, further elements may be provided for altering the sound from the transducers  10  and  20 . This may be seen in  FIG. 2 , wherein the output  11  connects the chamber  14  to the surroundings, and where the inlet  19  is in the chamber  16 , so that sound from the transducer  20  must pass also the diaphragm  12  in order to be output through the output  11 .  
         [0060]     In this embodiment, a hole or opening  13  is provided in the diaphragm  12 . The opening  13  may alternatively be provided in a support or suspension of the diaphragm. This opening  13  has a diameter of about 50-300 μm, whereby this opening is acoustically transparent for sound having a frequency lower than about 300 Hz. Other filtering characteristics may be obtained using openings of other dimensions. Any number of openings may be provided.  
         [0061]     Consequently, the diaphragm  12  will function excellently even though lower frequencies pass through it.  
         [0062]     Then, the transducer  20  may be used as a woofer outputting primarily sound with a frequency of 300 Hz or lower (such as 500-80 Hz), and the transducer  10  may be used as a tweeter providing sound of higher frequencies. It is noted that the second transducer  20  may output sound with any frequencies desired. Higher frequencies are simply filtered and will experience a loss when passing the diaphragm  12 .  
         [0063]     The opening  13  is not required in the diaphragm  12 , which will also convey sound there across when no opening  13  is provided. The opening  13  merely provides a simple manner of filtering sound from the second transducer  20 .  
         [0064]     Naturally, the electrical signals provided to the transducers  10 ,  20  may be filtered in order to determine the frequency output characteristics of the transducers. However, also other characteristics of the transducers may be adapted to output the desired sound characteristics, such as to function as tweeter or woofer. Thus, tweeters normally would have a lower moving mass than a woofer. This moving mass will aid in defining the resonance frequency of the transducer. This mass will in itself have an effect on the frequency response of the transducer.  
         [0065]     Another manner of affecting the sound output from the output  11  is to provide an acoustical filtering element between the transducers  10  and  20 , that is, between the inlet  19  and the output  21 .  
         [0066]     This filtering element may be provided, as is seen in  FIG. 3 , as a flat element  30  positioned in the sound path between the two transducers  10  and  20 . This element may just as well be positioned in the input  19  or the output  21 .  
         [0067]     This element  30  may be a simple grating or an element having a well-defined opening or hole therein. In this manner, the openings provided in the inlet  19  and the output  21  need not be that well-defined.  
         [0068]     Due to the positioning of the element  30  between two outer surfaces, which are normally at least substantially flat, this element may be rather large, more easily positioned, and may serve also other purposes, such as cushioning between the two transducers  10 ,  20  so as to avoid mechanical noise. Alternatively, the fastening of the element  30  to the transducers  10 ,  20  may also result in the fastening of the transducers  10 ,  20  to each other.  
         [0069]     It is clear that the element  30  may be provided in a number of manners and with a wide variety of functions.  
         [0070]      FIG. 4  illustrates another embodiment where, however, only the transducer  20  has been removed to enhance the understanding of the figure. In  FIG. 4 , an element  32  is positioned between the two transducers and defines, internally therein, an oblong channel  34  extending in a plane of the element  32  and of the outer surfaces of the transducers  10  and  20 . Also, the element  32  has an opening or openings  36  (one on either side, normally) toward the inlet  19  and the output  21  in order to function as a guide/filter of the sound travelling between the transducers  10  and  20 . As shown in  FIG. 4 , for example, a substantially circular opening  36  is provided at the upper portion of the oblong channel  34 .  
         [0071]     Naturally, the shape, size, dimensions of the channel  34  of the element  32  will affect the sound travelling there through. In addition, the element  32  may be used for more freely defining the positions of the inlet  19 , output  21  and generally the transducers  10 ,  20  in relation to each other.  
         [0072]     Another example of a shape of the channel  34  of the element  32  may be seen in  FIG. 5 , where the channel  34  is of a generally serpentine configuration.  
         [0073]     In addition, the channel  34  need not be a simple, oblong channel with the same cross-section along its length. The internal shape of this channel may be shaped in any desired manner in order to provide the desired filtering.  
         [0074]     In  FIGS. 4 and 5 , the element  32  is illustrated as having the channel  34  defined fully inside the element  32  with openings  36  from the channel  34  to the surface of the element  32  for sound to enter and exit. An alternative embodiment would be one wherein the outer surfaces of the transducers  10 ,  20  take part in the definition of the shape of the channel  34 , and where the element  32  only defines the walls/surfaces of the channel  34  in the plane of the surfaces of the transducers. In this situation, the openings  36  are not required in that the inlet  19  and output  21  will then open directly into the channel  34 .  
         [0075]     Alternatively, the channel  34  could be provided fully inside the wall part of one of the transducers  10 ,  20  and thereby be seen either as a filtering element or just as a part of the inlet  19  or output  21 . Naturally, the same shapes, etcetera, may be used in that situation.  
         [0076]     When generating the sound from multiple transducers, it is often desired to be able to feed the assembly a single signal corresponding to the sound desired but to electrically filter this signal and feed different signals to each of the transducers (such as to a tweeter and a woofer). This filtering may be performed using a crossover circuit filtering the signal input and feeding different signals to the two transducers.  
         [0077]     A circuit of this type may be seen in  FIG. 6 , which also illustrates the solder bumps  18 / 28  of the transducers. The positioning of the circuit and the solder bumps illustrates that the circuit actually is positioned within the housing of one of the transducers  10 / 20 , which thus has not only the two solder bumps for entry of the signal into the housing but a third solder bump (the second solder bump from the top) for use in outputting the signal from the crossover circuit to the other transducer. It is seen that the signal from the second solder bump from the top is fed to the lower transducer.  
         [0078]     In the present example, the electrical filter circuit is a single 100 nF capacitor adapted to remove lower frequencies. This capacitor may have one or more outer dimensions as small as 0.33 mm and may be used for feeding a tweeter.  
         [0079]     Thus, in the present situation, one of the transducers  10 ,  20  may receive the signal from, for example, an amplifier and provide two different signals, one of which is fed to the means moving the diaphragm of this transducer and one which is output from this transducer and fed to the other transducer.  
         [0080]     Thus, the present system may be provided as an assembled unit where the transducers  10  and  20  are pre-connected, and where only a connection between two solder bumps  18 / 28  are required to, for example, an amplifier in order to have an operational sound provider.  
         [0081]     Naturally, even though the embodiments described above comprise only two transducers, any number of transducers may be used. More transducers may be desired in order to provide a higher sound intensity or in order to provide a better quality of the sound, such as to combine special purpose transducers each especially suited to generate a particular sound or sound frequency interval. Thus, the use of both a tweeter, a woofer, and a mid-range transducer would be possible.  
         [0082]     Thus, a single output toward the surroundings may still be obtained, but these different transducers may be combined in any desired manner. One transducer output sound to the surroundings through two or more other transducers, or multiple transducers may be adapted to emit sound at different positions into the transducer with the output toward the surroundings. Different sizes, dimensions, shapes, filtering elements etc. may be used in order to obtain the desired sound.  
         [0083]     Also, more extra solder bumps may be provided on a transducer holding therein a crossover circuit, if this circuit is to feed more than one external transducer.  
         [0084]     While the present invention has been described with reference to one or more particular embodiments, those skilled in the art will recognize that many changes may be made thereto without departing from the spirit and scope of the present invention. Each of these embodiments and obvious variations thereof is contemplated as falling within the spirit and scope of the claimed invention, which is set forth in the following claims.