Patent Publication Number: US-11647325-B2

Title: Headphones

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to Japanese Patent Application No. 2020-129922, filed on Jul. 31, 2020. The entire disclosure of Japanese Patent Application No. 2020-129922 is hereby incorporated herein by reference. 
     BACKGROUND 
     Technical Field 
     One embodiment of this disclosure relates to headphones. 
     Background Information 
     In general, headphones include a speaker unit, a housing, and a baffle plate which serves as a support substrate for the speaker unit. 
     The headphones of Japanese Patent No. 6615185 disclose a configuration provided with a sheet  134  for suppressing acoustic reflections in the space between the baffle plate and the ear of the user. 
     SUMMARY 
     However, the headphones of Japanese Patent No. 6615185 are not provided with a bass reflex port. The headphones of Japanese Patent No. 6615185 cannot suppress resonance of the sound output from the speaker. 
     The object of one embodiment of this disclosure is to suppress the resonance of the sound output from the speaker in headphones provided with a bass reflex port. 
     The headphones according to one embodiment of this disclosure comprise a speaker unit, a baffle plate that fixes the speaker unit and includes a bass reflex port disposed therein, an ear pad disposed facing toward the baffle plate, and a sound absorber that is positioned between the baffle plate and the ear pad, and that has a hole facing the bass reflex port. 
     The headphones according to one embodiment of this disclosure suppress resonance of the sound output from the speaker. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a cross-sectional view of a headphone unit. 
         FIG.  2    is a partially exploded perspective view of the headphone unit. 
         FIG.  3 A  is an explanatory diagram showing a reference example of frequency characteristics of headphones not provided with a sound absorber. 
         FIG.  3 B  is an explanatory diagram showing one example of frequency characteristics of headphones provided with a sound absorber. 
         FIG.  4 A  is an explanatory diagram showing a reference example of phase characteristics of the headphones not provided with the sound absorber. 
         FIG.  4 B  is an explanatory diagram showing one example of phase characteristics of the headphones provided with the sound absorber. 
         FIG.  5    is a cross-sectional view of a headphone unit according to a modification. 
         FIG.  6    is a partially exploded perspective view of the headphone unit according to the modification. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Selected embodiments will now be explained with reference to the drawings. It will be apparent to those skilled in the field from this disclosure that the following descriptions of the embodiments are provided for illustration only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. 
     Headphones  1  according to the present embodiment will be described with reference to the drawings. Headphones  1  comprise a left-side headphone unit  11  and a right-side headphone unit  12 . The left-side headphone unit  11  and the right-side headphone unit  12  are connected by a headband (not shown). The headphones  1  have the same external appearance as generic headphones, and thus an illustration thereof has been omitted.  FIG.  1    is a cross-sectional view of one of the left-side headphone unit  11  and the right-side headphone unit  12 .  FIG.  2    is an exploded perspective view of the left-side headphone unit  11 . 
     The headphones  1  according to the present embodiment are connected by wire or wirelessly to an audio device, such as a music player, a sound mixer, or a smartphone. The headphones  1  receive audio signals from the audio device, convert the received audio signals into sound, and emit the sound. 
     The headphones  1  have an active noise cancelling (ANC) function. The headphones  1  according to the present embodiment are configured to boost the sound pressure in the low-frequency range by a bass reflex port using Helmholtz resonance. However, in this disclosure, provision of the ANC function is not essential. 
     As shown in  FIGS.  1  and  2   , each of the left-side headphone unit  11  and the right-side headphone unit  12  comprises a housing  2 , a baffle plate  3 , a chamber  4 , a speaker unit  5 , an ear pad  7 , and a sound absorber (sound-absorbing material)  70 . In addition, each of the left-side headphone unit  11  and the right-side headphone unit  12  can further comprise a vibration damper  6  disposed between the speaker unit  5  and the chamber  4 . However, the vibration damper  6  can be omitted. Moreover, at least one of the left-side headphone unit  11  and the right-side headphone unit  12  can further comprise a battery  81 . The battery  81  is disposed on an outer surface of a bottom wall  40  of the chamber  4 . 
     The left-side headphone unit  11  will be described in detail. The left-side headphone unit  11  and the right-side headphone unit  12  have the same configuration. Therefore, here, the left-side headphone unit  11  will be described as a representative example. 
     As shown in  FIGS.  1  and  2   , the housing  2  is in the form of a hollow cylinder with an open first end that faces the baffle plate  3 . The speaker unit  5  and the chamber  4  are disposed inside the housing  2 . Through-holes  21  are formed in the side wall of the housing  2 . The through-holes  21  are provided primarily for conducting air. The housing  2  blocks disturbance noise from the outside. The chamber  4  disposed inside the housing  2  can thus prevent resonance caused by external disturbances. 
     The baffle plate  3  is disk-shaped. The baffle plate  3  is connected to the housing  2  and covers the open end of the housing  2 . That is, the peripheral edge of the baffle plate  3  is connected to the open end of the housing  2 . The baffle plate  3  includes a grill  31  formed with a plurality of openings for allowing the sound from the speaker unit  5  to pass through at the center portion facing a sound-emitting part  50  of the speaker unit  5 . In addition, the baffle plate  3  includes a first port  32  for bass reflex, and the first port  32  passes through in the thickness direction. 
     The speaker unit  5  is disposed on the center portion (grill  31 ) of the baffle plate  3 . The speaker unit  5  has an active noise cancelling (ANC) function. 
     The chamber  4  is arranged in the space formed by the housing  2  and the baffle plate  3 . The chamber  4  is in the form of a hollow cylinder with an open first end on the baffle plate  3  side. The open end of the chamber  4  is connected to the baffle plate  3 . That is, the baffle plate  3  is disposed to cover the open end of the chamber  4 . The chamber  4  contains the speaker unit  5 . The chamber  4  is disposed to cover the outer circumferential surface and rear surface  51  of the speaker unit  5 . More specifically, the chamber  4  is disposed such that an inner surface  401  of a bottom wall  40  and the rear surface  51  of the speaker unit  5  face each other. The chamber  4  also has the function of insulating the sound of the speaker unit  5 . 
     The chamber  4  has a second port  41  that is formed on the bottom wall  40  for bass reflex. The second port  41  is in the form of a cylinder with two open ends and projects toward the outer side of the bottom wall  40 . In this case, the speaker unit  5  is disposed inside the chamber  4  so as not to block the opening of the second port  41 . 
     The internal spaces of the chamber  4  and the housing  2  communicate with each other through the second port  41 . As a result, the chamber  4  and the housing  2  function as the cavity of a Helmholtz resonator. Thus, the second port  41  and the first port  32  function as resonance tubes. 
     The ear pad  7  is provided on the baffle plate  3  side, opposite the side on which the speaker unit  5  is disposed. The ear pad  7  is cylindrical in form. The central portion of the ear pad  7  is open, so that sound emitted from the sound-emitting part  50  of the speaker unit  5  reaches the outside (i.e., the ear of the user). The ear pad  7  is connected to the baffle plate  3  via cylindrical base material  75  at the peripheral edges. A space corresponding to the thickness of the base material  75  is formed between the ear pad  7  and the baffle plate  3 . The sound absorber  70  is disposed between the baffle plate  3  and the car pad  7 , filling the space. The sound absorber  70  is made up of porous material, such as glass wool, felt, or urethane. The sound absorber  70  prevents sounds output from the speaker unit  5  from being reflected and interfering with each other in the space. 
     The sound absorber  70  is cylindrically formed. The central portion of the sound absorber  70  is open, so that the sound emitted from the sound-emitting part  50  of the speaker unit  5  reaches the ear of the user. The sound absorber  70  has a central opening  72  (opening) at a position facing toward the speaker unit  5 . The central opening  72  corresponds to the opening of this disclosure. The area of the central opening  72  is the same as the area of the front surface of the speaker unit  5 . 
     The sound absorber  70  also has an opening  71  (hole) at the position facing the first port  32 . The opening  71  corresponds to the hole of this disclosure. The diameter of the opening  71  is preferably the same as the diameter of the first port  32  or larger than the diameter of the first port  32 . In addition, the sound absorber  70  is attached to the baffle plate  3 , and the sound absorber  70  and the ear pad  7  are at least partially spaced apart from each other with a gap therebetween. In this embodiment, there is a gap  73  that is entirely arranged between the sound absorber  70  and the ear pad  7  in the vertical direction as viewed in  FIG.  1   . The resonance sound output from the first port  32  reaches the central opening of the ear pad  7  through the opening  71  and the gap  73 , and reaches the ear of the user. 
     The sound absorber  70  thereby prevents interference of the sound output from the speaker unit  5  and causes the resonance sound output from the first port  32  to reach the ear of the user. The thickness of the gap  73 , which is the thickness between the sound absorber  70  and the ear pad  7  in the vertical direction as viewed in  FIG.  1   , is preferably larger than the diameter of the first port  32  which is the bass reflex port. If the thickness of the gap  73  is less than or equal to the diameter of the first port  32 , the gap  73  can also function as a bass reflex port. In this case, the resonance frequency takes on a value that differs from the design, and the sound quality can differ from the target sound quality. If the thickness of the gap  73  is greater than the diameter of the first port  32 , the gap  73  does not function as a bass reflex port, so that the desired sound quality can be reproduced. In the present embodiment, the first port  32  has a circular cross section, but the cross-sectional shape of the bass reflex port need not be circular. For example, the cross-sectional shape of the bass reflex port can be elliptical or polygonal. Even when the cross-sectional shape of the bass reflex port is elliptical, the thickness of the gap  73  is preferably larger than the diameter (length of the major axis). Even when the cross-sectional shape of the bass reflex port is polygonal, the thickness of the gap  73  is preferably greater than the diameter of the bass reflex port (the length of longest diagonal). 
       FIG.  3 A  is an explanatory diagram showing an example of the frequency characteristics of the left-side headphone unit and the right-side headphone unit in which the sound absorber  70  is not provided as a reference example. Aside from the presence/absence of the sound absorber  70 , the reference headphones have the same configuration as the headphones  1  of the present embodiment.  FIG.  3 B  is an explanatory diagram showing an example of the frequency characteristics of the left-side headphone unit  11  and the right-side headphone unit  12  of the present embodiment provided with the sound absorber  70 . 
     As shown in  FIG.  3 A , the frequency characteristics of the left-side headphone unit and right-side headphone unit of the reference example include numerous dips (minimal components), particularly in the upper midrange (2 kHz-10 kHz). These dips are caused by the reflections and interference of the output sound of the speaker unit  5  between the baffle plate  3  and the ear pad  7 . 
     In the headphones  1  of the present embodiment, on the other hand, the sound absorber  70  is disposed between the baffle plate  3  and the ear pad  7  in order to suppress interference. Therefore, as shown in  FIG.  3 B , in the headphones  1  of the present embodiment, dips are suppressed in the upper midrange. More specifically, in the headphones  1  of the present embodiment, the large 3-kHz dip of the reference example is almost gone. In contrast, due to the presence of the gap  73  between the opening  71  and the ear pad  7 , the sound absorber  70  does not obstruct the resonance sound output from the first port  32 , and the frequency characteristics in the lower midrange below 1 kHz are not deteriorated. Further, by the configuration of the present embodiment, the frequency characteristics in the lower midrange below 1 kHz become flatter. Since the headphones  1  of the present embodiment do not add extraneous frequency characteristics to the input sound in the lower midrange below 1 kHz, sound closer to the original sound can be output. 
     Thus, the headphones  1  of the present embodiment can improve the sound quality by the sound absorber  70 . 
       FIG.  4 A  is an explanatory diagram showing an example of the phase characteristics of the left-side headphone unit and the right-side headphone unit of the reference example in which the sound absorber  70  is not provided.  FIG.  4 B  is an explanatory diagram showing an example of the phase characteristics of the left-side headphone unit  11  and the right-side headphone unit  12  of the present embodiment provided with the sound absorber  70 . 
     As shown in  FIG.  4 A , in the reference headphones, reflections and interference of the output sound of the speaker unit  5  between the baffle plate  3  and the ear pad  7  occur in the midrange of approximately 300 Hz to 2 kHz and causes phase delays of up to about 80°. 
     In the headphones  1  of the present embodiment, on the other hand, the phase delay is improved to about 60° in the midrange of approximately 300 Hz to 2 kHz, as shown in  FIG.  4 B . In contrast, by the gap  73  between the opening  71  and the ear pad  7 , the sound absorber  70  of the present embodiment does not obstruct the resonance sound output from the first port  32 , so that the midrange phase characteristics are also not deteriorated. 
     Thus, the phase characteristics of the headphones  1  of the present embodiment are improved by the sound absorber  70 , and the effect of the ANC function is also improved. 
     The second port  41  of the chamber  4  is not limited to the embodiment example described above. The second port  41  can be provided on either the bottom wall  40  or the side wall of the chamber  4 . 
     Modification 
     The headphones  1  according to a modification will be described with reference to  FIG.  5   .  FIG.  5    is a cross-sectional view of a left-side headphone unit  11 A according to the modification.  FIG.  6    is a partially exploded perspective view of the left-side headphone unit  11 A according to the modification. Components that are identical to those of the embodiment described above have been assigned the same reference symbols, and their descriptions have been omitted. Since the left-side headphone unit  11 A and the right-side headphone unit  12 A of the modification have the same structure, only the left-side headphone unit  11 A will be shown in this modification. 
     The headphones  1  of the modification are different from the embodiment described above in that a sound absorber  70 A is included. The thickness of the sound absorber  70 A is partially the same as the distance between the baffle plate  3  and the ear pad  7 . Instead of the gap  73  of the embodiment described above, the sound absorber  71  and the ear pad  7  are partially spaced apart from each other with a groove  71 A as a gap therebetween. More specifically, the sound absorber  70 A has, as the gap, the groove  71 A formed from a position facing the first port  32  to a position facing toward the speaker unit  5 , and the groove  71  connects the opening  71  and the central opening  72  (portion facing the sound-emitting part  50 ). 
     That is, the sound absorber  70 A fills almost all of the space between the baffle plate  3  and the ear pad  7 , but is provided with the groove  71 A as a gap for allowing the resonance sound output from the first port  32  to reach the ear of the user. 
     The cross sectional area of the groove  71 A is preferably greater than the cross sectional area of the first port  32 . By making the cross sectional area of the groove  71 A greater than the cross sectional area of the first port  32 , the groove  71 A can be prevented from functioning as a bass reflex port, and the desired sound quality can be reproduced. The cross-sectional shape of the groove  71 A can be any shape, such as circular, elliptical, or polygonal. 
     The description of the present embodiment is exemplary in all respects and should not be considered restrictive. The scope of this disclosure is indicated by the Claims section, and not the embodiment described above. Furthermore, the scope of this disclosure is intended to include all modifications within the meaning and scope equivalent to that of the claims.