Patent Publication Number: US-8121301-B2

Title: Earpiece, electronic device and communication device

Description:
TECHNICAL FIELD 
     The present invention relates to an earpiece, an electronic device, and a communication device. 
     BACKGROUND ART 
     Both a sound volume and a sound quality are deteriorated in an earpiece of the mobile terminal device, or the like since leakage of sounds generated due to a clearance between the user&#39;s ear and the earpiece gives rise to a decrease in a sound pressure in a low-frequency band of the sound pressure-frequency characteristic. 
     In particular, the earpiece of the stationary terminal device has a relatively large shape and it is easy to cover the user&#39;s ear fully with this earpiece, but the earpiece of the mobile terminal device has a plane shape because such earpiece is formed integrally with other parts such as the display portion, and the like. Therefore, it is difficult to cover the user&#39;s ear fully with the earpiece and the leakage of sounds takes place more conspicuously, and thus a sound volume and a sound quality are deteriorated considerably. 
     As the reform measures for this, the measure for reducing the leakage by fitting a ring gasket to a contact portion between the earpiece and the user&#39;s ear to improve a sealing performance of the user&#39;s ear with the earpiece (see Patent Literature 1, for example), the measure for controlling a frequency characteristic by a signal processing means by fitting a pressure sensor near the earpiece to sense a contact state between the earpiece and the user&#39;s ear (see Patent Literature 2, for example), and the like have been proposed.
     Patent Literature 1: JP-T-2002-501683   Patent Literature 2: JP-A-8-102991   

     DISCLOSURE OF THE INVENTION 
     Problems that the Invention is to Solve 
     However, in the earpiece in the prior art, there existed the circumstances that, since the parts must be added to compensate for the sound pressure characteristic due to the leakage of sounds caused by the clearance between the earpiece and the user&#39;s ear, an increase in cost and restrictions on design and shape arise. 
     The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an earpiece, an electronic device, and a communication device capable of reducing the influence of leakage of sounds from a clearance between the earpiece and an ear not to need an addition of parts. 
     Means for Solving the Problems 
     An earpiece of the present invention includes an electromechanical acoustic transducer having a diaphragm, for generating a sound by vibrating the diaphragm in response to an electric signal; a case on which a sound hole is provided and in which the electromechanical acoustic transducer is housed; and a holding member for holding the electromechanical acoustic transducer in the case; wherein the electromechanical acoustic transducer has a sound pressure-frequency characteristic that is compensated in advance such that the sound pressure-frequency characteristic is planarized in a condition that the generated sound is leaked from an ear being covered with the case. 
     According to this configuration, the sound pressure-frequency characteristic of the electromechanical acoustic transducer is compensated in advance such that the sound pressure-frequency characteristic is planarized under the condition that the sounds are leaked from the clearance between the case and the user&#39;s ear. Therefore, the influence of the leakage can be reduced without any addition of parts. 
     Also, in the earpiece of the present invention, the sound pressure-frequency characteristic is given as a characteristic that is compensated based on a difference between the sound pressure-frequency characteristic derived when a leakage is caused and the sound pressure-frequency characteristic derived when no leakage is caused. 
     According to this configuration, the sound pressure-frequency characteristic is compensated based on the difference between the sound pressure-frequency characteristics derived when the leakage of sounds from the clearance between the case and the user&#39;s ear is caused and when no leakage is caused. Therefore, a good characteristic of the electromechanical acoustic transducer can be set. 
     Also, in the earpiece of the present invention, the sound pressure-frequency characteristic is compensated such that a lowest resonance frequency is lowered. 
     According to this configuration, a reduction in sound pressure in the low-frequency band due to the leakage of the sounds from the clearance between the case and the user&#39;s ear can be prevented. 
     An electronic device of the present invention includes the above earpiece. According to this configuration, the sound pressure-frequency characteristic of the electromechanical acoustic transducer is compensated in advance such that the sound pressure-frequency characteristic is planarized under the condition that the sounds are leaked from the clearance between the case and the user&#39;s ear. Therefore, the influence of the leakage can be reduced without any addition of parts. 
     A communication device of the present invention includes an antenna for receiving a radio signal; a signal outputting portion for outputting an electric signal in response to the received radio signal; an electromechanical acoustic transducer having a diaphragm, for generating a sound by vibrating the diaphragm in response to the electric signal being output from the signal outputting portion; a case on which a sound hole is provided and in which the electromechanical acoustic transducer is housed; a holding member for holding the electromechanical acoustic transducer in the case; wherein the electromechanical acoustic transducer has a sound pressure-frequency characteristic that is compensated in advance such that the sound pressure-frequency characteristic is planarized in a condition that the generated sound is leaked from an ear being covered with the case. 
     According to this configuration, the sound pressure-frequency characteristic of the electromechanical acoustic transducer is compensated in advance such that the sound pressure-frequency characteristic is planarized under the condition that the sounds are leaked from the clearance between the case and the user&#39;s ear. Therefore, the influence of the leakage can be reduced without any addition of parts. 
     Advantages of the Invention 
     According to the present invention, the earpiece, the electronic device, and the communication device, capable of reducing the influence of leakage of sounds from a clearance between the earpiece and an ear not to need an addition of parts can be provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  A view showing an earpiece according to a first embodiment of the present invention. 
         FIG. 2  A view showing an electromechanical acoustic transducer of the earpiece according to the first embodiment of the present invention. 
         FIG. 3  A view showing a sound pressure-frequency characteristic of the electromechanical acoustic transducer when no compensation is made. 
         FIG. 4  A view showing an amount of compensation-frequency characteristic of the electromechanical acoustic transducer. 
         FIG. 5  A view showing a sound pressure-frequency characteristic of the electromechanical acoustic transducer when compensation is made. 
         FIG. 6  A view showing a mobile terminal device according to a second embodiment of the present invention. 
         FIG. 7  A view showing an electronic device according to a third embodiment of the present invention. 
     
    
    
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
           10  electromechanical acoustic transducer 
           11  case 
           12  sound hole 
           13  holding member 
           14  user&#39;s ear 
           20 ,  30  first case 
           21 ,  31  second case 
           22  antenna 
           23 ,  32  hinge 
           24 ,  34  display portion 
           25  operation portion 
           26  receiver circuit 
           27  signal outputting portion 
           33  controlling portion 
           35  signal outputting portion 
           100  earpiece 
           101  yoke 
           102  magnet 
           103  plate 
           104  voice coil 
           105  diaphragm 
           106  frame 
           200  communication device 
           300  electronic device 
       
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     First Embodiment 
       FIG. 1  is a view showing an earpiece according to a first embodiment of the present invention, wherein  FIG. 1(   a ) is a plan view of the earpiece and  FIG. 1(   b ) is a sectional view of the earpiece taken along a dot-dash line I-I in  FIG. 1(   a ). 
     As shown in  FIG. 1 , an earpiece  100  of the first embodiment includes an electromechanical acoustic transducer  10  for outputting sounds in response to an electric signal, a case  11  on which a sound hole  12  is provided and in which the electromechanical acoustic transducer  10  is housed, and a holding member  13  for holding the electromechanical acoustic transducer  10  in the case  11 . 
     The electromechanical acoustic transducer  10  has a diaphragm and generates the sounds by vibrating the diaphragm in response to the electric signal.  FIG. 2  is a view showing an electromechanical acoustic transducer of the earpiece according to the first embodiment of the present invention, wherein  FIG. 2(   a ) is a top view of the electromechanical acoustic transducer and  FIG. 2(   b ) is a sectional view of the electromechanical acoustic transducer taken along a dot-dash line II-II in  FIG. 2(   a ). 
     As shown in  FIG. 2 , the electromechanical acoustic transducer  10  has a yoke  101 , a magnet  102  provided on the yoke  101 , a plate  103  provided on the magnet  102 , a voice coil  104 , a diaphragm  105 , and a frame  106 . 
     The yoke  101 , the magnet  102 , and the plate  103  constitute a magnetic circuit having an air gap G. The voice coil  104  is constructed by winding an electric wire, and is adhered to the diaphragm  105  and arranged in the air gap G. Then, a magnetic flux generated in the air gap G in response to the given electric signal generates a force based on the electromagnetic induction. The diaphragm  105  is vibrated by the force generated in the voice coil  104  to generate the sounds. The frame  106  holds the yoke  101  and the diaphragm  105 . 
     According to the above earpiece  100 , when the user puts the case  11  to the user&#39;s ear to hear the received sound, the sound hole  12  of the case  11  is not perfectly covered with user&#39;s ear  14 . Therefore, the sounds emitted from the electromechanical acoustic transducer  10  via the sound hole  12  are separated into the sound that is transmitted directly to the user&#39;s ear  14  and the sound that leaks from a clearance between the user&#39;s ear  14  and the case  11 . As a result, the characteristic of sound reaching from the electromechanical acoustic transducer  10  to the user&#39;s ear  14  is affected by the leakage of sounds. 
       FIG. 3  is a view showing a sound pressure-frequency characteristic of the electromechanical acoustic transducer when no compensation is made, and shows a characteristic  301  when no leakage is caused and a characteristic  302  when the leakage is caused. In this case, a dynamic receiver of a bore diameter φ 10 mm was used in measuring these characteristics. Also, the characteristic  301  derived when no leakage is caused was measured under the condition that no leakage is caused by using the IEC-318 coupler, and the characteristic  302  derived when the leakage is caused was measured under the condition that the leakage is caused artificially by using the Head and Torso Simulator (abbreviated as “HATS” hereinafter). A voltage whose root-mean-square-value is 180 [mV] was applied to the electromechanical acoustic transducer  10  in respective measurements. 
     As shown in  FIG. 3 , in comparison between the characteristic  301  derived when no leakage is caused and the characteristic  302  derived when the leakage is caused, a sound pressure in a low-frequency band, especially a level of an output sound pressure below the lowest resonance frequency f 0 , was remarkably deteriorated in the characteristic  302  derived when the leakage is caused. In other words, the influence of the leakage between the case  11  and the user&#39;s ear  14  appeared in the sound pressure-frequency characteristic. 
     Therefore, in the present embodiment, a change in the sound pressure-frequency characteristic due to the leakage is measured, and then the sound pressure-frequency characteristic of the electromechanical acoustic transducer  10  is compensated beforehand based on this change. Thus, a good sound pressure can be obtained under the condition that is close to the actual using condition and the leakage is caused. 
       FIG. 4  is a view showing an amount of compensation-frequency characteristic of the electromechanical acoustic transducer. An amount-of-compensation characteristic  41  shown in  FIG. 4  is a difference calculated when the characteristic  301  derived when no leakage is caused was subtracted from the characteristic  302  derived when the leakage is caused and shown in  FIG. 3 . The compensation of the sound pressure-frequency characteristic of the electromechanical acoustic transducer  10  was made by offsetting the sound pressure-frequency characteristic of the electromechanical acoustic transducer  10  based on this amount-of-compensation characteristic  41 . 
       FIG. 5  is a view showing a sound pressure-frequency characteristic of the electromechanical acoustic transducer when compensation is made, and shows a characteristic  501  when no leakage is caused and a characteristic  502  when the leakage is caused. In this case, a dynamic receiver of a bore diameter φ 13 mm was used in measuring these characteristics. Also, the characteristic  501  derived when no leakage is caused was measured under the condition that no leakage is caused by using the IEC-318 coupler, and the characteristic  502  derived when the leakage is caused was measured under the condition that the leakage is caused artificially by using the Head and Torso Simulator (abbreviated as “HATS” hereinafter). A voltage whose root-mean-square-value is 180 [mV] was applied to the electromechanical acoustic transducer  10  in respective measurements. 
     As shown in  FIG. 5 , the characteristic  502  derived when the leakage is caused was planarized rather than the characteristic  302  derived when the leakage is caused and shown in  FIG. 3 . In particular, the level of the output sound pressure in the low-frequency band was improved. In this manner, the compensation is applied in advance to the sound pressure-frequency characteristic of the electromechanical acoustic transducer  10 , so that a good sound pressure can be obtained under the condition that is close to the actual using condition and the leakage is caused. 
     Next, an example of a method of compensating the sound pressure-frequency characteristic of the electromechanical acoustic transducer  10  will be explained hereunder. As shown in  FIG. 3 , the characteristic derived when no leakage is caused was deteriorated especially in the low-frequency band under the condition that no compensation is made. Therefore, as shown in  FIG. 4 , an absolute value of an amount of compensation (difference between the characteristic derived when the leakage is caused and the characteristic derived when no leakage is caused) became larger in the low-frequency band. 
     In other words, since the compensation is made such that the lowest resonance frequency f 0  of the electromechanical acoustic transducer  10  is lowered, the planarized sound pressure-frequency characteristic was obtained when the leakage is caused. 
     Here, the lowest resonance frequency f 0  is defined by following Formula 1. Where, Cms is a diaphragm compliance, and Mms is a vibration system mass containing masses of an adhesive to adhere the voice coil onto the diaphragm, and the like. 
     
       
         
           
             
               
                 
                   
                     f 
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                     0 
                   
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                       1 
                       
                         2 
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                         ⁢ 
                         π 
                       
                     
                     · 
                     
                       1 
                       
                         
                           Cms 
                           · 
                           Mms 
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Formula 
                     ⁢ 
                     
                         
                     
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                     1 
                   
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     Here, the diaphragm compliance Cms depends on an elastic modulus of the material used as the diaphragm and a material thickness of the diaphragm. In this case, the diaphragm compliance Cms is expressed by Cms=x/F [m/N] in theory, where F [N] is a force applied to the diaphragm and x [m] is a distance over which the diaphragm is expanded. 
     As the material used as the diaphragm, there are PEI (polyetherimide), PEN (polyethylene naphthalate), PET (polyethylene terephthalate), elastomer, and the like, for example. 
     Therefore, the compensation is made by changing the elastic modulus of the material used as the diaphragm, the material thickness of the diaphragm, the vibration system mass, etc. to lower the lowest resonance frequency f 0 . According to Formula 1, the lowest resonance frequency f 0  can be lowered in theory by increasing both the diaphragm compliance Cms and the vibration system mass Mms, but these combinations must be constructed actually. 
     In the example shown in  FIG. 3 , the lowest resonance frequency f 0  is about 550 [Hz], as indicated in the characteristic  301  derived when no leakage is caused. In this case, when the sound pressure-frequency characteristic is compensated such that the lowest resonance frequency f 0  is lowered to at least 550 [Hz] or less, preferably about 430 [Hz] or less, a good characteristic can be obtained under the condition that the leakage is caused. 
     Table 1 shows an example of combinations of a material thickness t of the diaphragm and the vibration system mass Mms when PEI is used as the material of the diaphragm. In Table 1, shaded portions show the combinations that satisfy the condition that the lowest resonance frequency f 0  is about 430 [Hz] or less. It is preferable that, when the material thickness t of the diaphragm made of PEI is 8.6 [μm], for example, the vibration system mass Mms should be set to 16 to 32 [mg]. 
     
       
         
           
               
             
               
                   
               
             
            
               
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
            
           
         
       
     
     Also, Table 2 shows an example of combinations of a material thickness t of the diaphragm and the vibration system mass Mms when PEN is used as the material of the diaphragm. In Table 1, shaded portions show the combinations that satisfy the condition that the lowest resonance frequency f 0  is about 430 [Hz] or less. 
     
       
         
           
               
             
               
                   
               
             
            
               
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
            
           
         
       
     
     In the examples given in Table 1 and Table 2, the sound pressure-frequency characteristic can be compensated when the electromechanical acoustic transducer  10  is constructed based on the combination of the material thickness t of the diaphragm and the vibration system mass Mms in the shaded portion. 
     According to such first embodiment of the present invention, the sound pressure-frequency characteristic of the electromechanical acoustic transducer is compensated in advance such that the sound pressure-frequency characteristic is planarized under the condition that the sounds are leaked from the clearance between the case and the user&#39;s ear. As a result, the influence of the leakage can be reduced without any addition of parts. 
     In the present embodiment, the case where the HATS is used to generate artificially the leakage of sounds is explained. In this case, the characteristic in the condition that the user actually uses the earpiece  100  may be measures by a probe microphone, or the like as the characteristic derived when the leakage is caused, and then the amount of compensation-frequency characteristic shown in  FIG. 4  may be derived. 
     Also, in the present embodiment, the case where the dynamic receiver is used as the electromechanical acoustic transducer  10  is explained. In this case, a dynamic speaker, a ceramic receiver, or a ceramic speaker may be used. 
     Second Embodiment 
       FIG. 6  is a view showing a mobile terminal device according to a second embodiment of the present invention, wherein  FIG. 6(   a ) is an external perspective view of the mobile terminal device and  FIG. 6(   b ) is a schematic internal configuration of the communication device. In  FIG. 6 , the same reference symbols are affixed to the redundant portions with those in  FIG. 1  explained in the first embodiment. In the present embodiment, explanation will be made by taking a folding cellular phone as an example of a communication device  200 . But the present embodiment is not limited to the cellular phone, and may be applied to an electronic device having a communication function such as a transceiver, a stationary communication equipment, and the like. 
     As shown in  FIG. 6 , the communication device  200  includes a first case  20 , a second case  21 , an antenna  22  provided to the first case  20 , a hinge  23  for joining the first case  20  and the second case  21  to swing, a display portion  24 , an operation portion  25 , a receiver circuit  26  for converting a radio signal that the antenna  22  received into an electric signal, a signal outputting portion  27  for outputting the electric signal fed from the receiver circuit  26 , and the earpiece  100  for outputting a sound in response to the electric signal output from the signal outputting portion  27 . 
     In the communication device  200  of the present embodiment, a received sound is reproduced from the sound hole  12  when the electric signal indicating the received sound received via the antenna is applied. In this case, the earpiece  100  fulfils a function of the receiver. 
     According to such second embodiment of the present invention, the sound pressure-frequency characteristic of the electromechanical acoustic transducer is compensated in advance such that the sound pressure-frequency characteristic is planarized under the condition that the sounds are leaked from the clearance between the case and the user&#39;s ear. Therefore, the influence of the leakage can be reduced without any addition of parts. As a result, the influence of the leakage can be reduced not make any change in design or shape of the mobile terminal device. 
     Here, in the first embodiment, the characteristic derived when the sound is leaked through the clearance between the case of the earpiece  100  and the user&#39;s ear is measured as the characteristic of the electromechanical acoustic transducer  10  of the earpiece  100  derived when the leakage is caused, and then an amount of compensation is derived based on the measured result. In contrast, in the mobile terminal device of the present embodiment, the characteristic derived when the sound is leaked through the clearance between the case in which the earpiece  100  of the communication device  200  is housed and the user&#39;s ear may be measured as the characteristic derived when the leakage is caused, and then an amount of compensation may be derived based on the measured result. 
     Third Embodiment 
       FIG. 7  is a view showing an electronic device according to a third embodiment of the present invention, wherein  FIG. 7(   a ) is an external perspective view of the electronic device and  FIG. 7(   b ) is a schematic internal configuration of the electronic device. In  FIG. 7 , the same reference symbols are affixed to the redundant portions with those in  FIG. 1  explained in the first embodiment. In the present embodiment, explanation will be made by taking a folding mobile terminal (PDA) device as an example of an electronic device  300 . However, the present embodiment is not limited to the PDA, and may be applied to a stationary electronic device. 
     As shown in  FIG. 7 , an electronic device  300  of the present embodiment includes a first case  30 , a second case  31 , a hinge  32  for joining the first case  30  and the second case  31  to swing, a controlling portion  33  provided to the second case  31  to process an image signal and a sound signal, a display portion  34  provided to the first case  30  to display operation menu icons, etc., a signal outputting portion  35  for amplifying a signal from the controlling portion  33 , and the earpiece  100  for outputting the sound in response to an electric signal output from the signal outputting portion  35 . 
     In the electronic device  300  of the present embodiment, when the electric signal indicating the sound in answer to the user&#39;s operation is applied, the sound is reproduced through the sound hole  12  of the earpiece  100 . According to such third embodiment of the present invention, the sound pressure-frequency characteristic of the electromechanical acoustic transducer is compensated previously such that the sound pressure-frequency characteristic is planarized under the condition that the sounds are leaked from the clearance between the case and the user&#39;s ear. Therefore, the influence of the leakage can be reduced without any addition of parts. As a result, the influence of the leakage can be reduced not make any change in design or shape of the electronic device. 
     Here, in the first embodiment, the characteristic derived when the sound is leaked through the clearance between the case of the earpiece  100  and the user&#39;s ear is measured as the characteristic of the electromechanical acoustic transducer  10  of the earpiece  100  derived when the leakage is caused, and then an amount of compensation is derived based on the measured result. In contrast, in the mobile terminal device of the present embodiment, the characteristic derived when the sound is leaked through the clearance between the case in which the earpiece  100  of the mobile terminal device  200  is housed and the user&#39;s ear may be measured as the characteristic derived when the leakage is caused, and then an amount of compensation may be derived based on the measured result. 
     The present invention is explained in detail with reference to the particular embodiments. But it is apparent for those skilled in the art that various variations and modifications can be applied without departing from a spirit and a scope of the present invention. 
     This application is based upon Japanese Patent Application (Patent Application No. 2005-106329) filed Apr. 1, 2005; the entire contents of which are incorporated herein by reference. 
     INDUSTRIAL APPLICABILITY 
     According to the present invention, the earpiece, the electronic device, and the communication device of the present invention possess such an advantage that the influence of leakage of sounds from the clearance between the earpiece and the ear can be reduced not to need an addition of parts, and is useful to the cellular phone, or the like.