Patent Publication Number: US-2023157895-A1

Title: High frequency noise filtering earplug using metasurface

Description:
TECHNICAL FIELD 
     The present disclosure relates to an earplug and, more partucularly, to an earplug that can reduce high-frequency noise using a metasurface. 
     BACKGROUND ART 
     In general, earplugs are worn on ears to protect a user&#39;s hearing from noise, to be used for blocking water from entering ears, and to improve concentration while working or studying. Recently, earplugs that block noise in a specific range through noise canceling technology have been released. 
     However, earplugs with a noise canceling function are expensive and require charging, which can be inconvenient. For earplugs at a relatively low price, the disadvantage is that their functions are very limited since they have limited functionality and are intended only for wearing comfort, sound insulation, and soundproofing. Also, there is a problem of communication difficulties because all bands of sound are blocked. 
     In the case of optional noise-shielding earplugs with a conventional external noise path, simply a sound absorbing material is used or a vortex is created during the movement of a sound wave by designing the path of the sound wave in a complicated way to reduce the noise. This structure has a problem in that the overall noise reduction amount is not large and it is difficult to shield the low-frequency sounds from the high-frequency sounds. 
     DISCLOSURE 
     Technical Problem 
     The present disclosure has been made keeping in mind the problems occurring in the related art, and an objective of the present disclosure is to provide an earplug that can effectively reduce high-frequency noise. 
     Technical Solution 
     A high-frequency noise filtering earplug using a metasurface according to an embodiment of the present disclosure may include: an eartip with an internal passage; an interference attenuation module having a damping passage for reducing noise and a first reflective cavity that is connected to the damping passage and reflects incident sound waves and transmits the sound waves to the damping passage; and a connecting tube installed between the eartip and the interference attenuation module to connect the internal passage and the damping passage. 
     The interference attenuation module according to an embodiment of the present disclosure may include a first damping protrusion protruding in the lateral direction of the damping passage, and a first reflective cavity may be formed inside the first damping protrusion. 
     The interference attenuation module according to an embodiment of the present disclosure may include two first damping protrusions, and the first damping protrusions may be spaced apart from each other with the damping passage interposed therebetween. 
     The interference attenuation module according to an embodiment of the present disclosure may include a second damping protrusion protruding in a direction crossing the first damping protrusion, and a second reflective cavity may be formed inside the second damping protrusion. 
     The second reflective cavity according to an embodiment of the present disclosure may have a smaller volume than the first reflective cavity. 
     A first opening connecting the first reflective cavity and the damping passage may be formed in the first reflective cavity according to an embodiment of the present disclosure, a second opening connecting the second reflective cavity and the damping passage may be formed in the second reflective cavity, and the first opening and the second opening may be spaced apart from each other in the longitudinal direction of the damping passage. 
     The first damping protrusion according to an embodiment of the present disclosure may be more protruding to the rear than the second damping protrusion. 
     The interference attenuation module according to an embodiment of the present disclosure may further include a casing surrounding the first damping protrusion and the second damping protrusion, and a noise inlet through which sound waves are introduced may be formed in the casing. 
     A third reflective cavity for reflecting sound waves may be formed between the casing and the first damping protrusion and the second damping protrusion according to an embodiment of the present disclosure. 
     The first damping protrusion according to an embodiment of the present disclosure may include a first body and a second body slidable to the first body, so that a volume of the first reflective cavity may be increased or decreased. 
     Advantageous Effects 
     As described above, the high-frequency noise filtering earplug using a metasurface according to an embodiment of the present disclosure has reflective cavities, which are metasurfaces on which high-frequency noise may be reflected, so that the incident high-frequency noise is reflected inside the reflective cavities, and the phase-shifted noise interferes with the noise incident in the damping passage, thus the high-frequency noise can be attenuated by interference. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG.  1    is a perspective view showing an earplug according to a first embodiment of the present disclosure; 
         FIG.  2    is a cutaway perspective view of the earplug according to the first embodiment of the present disclosure, cut in the transverse direction; 
         FIG.  3    is a cutaway perspective view of the earplug according to the first embodiment of the present disclosure, cut in the longitudinal direction; 
         FIG.  4    is a perspective view showing an earplug according to a second embodiment of the present disclosure; 
         FIG.  5    is a cross-sectional view of the earplug according to the second embodiment of the present disclosure; 
         FIG.  6    is a photograph showing the simulation results of emitting a 1000 Hz sound wave to the earplug according to the second embodiment of the present disclosure; 
         FIG.  7    is a photograph showing the simulation results of emitting a 4000 Hz sound wave to the earplug according to the second embodiment of the present disclosure; 
         FIG.  8    is a graph showing the results of emitting the 1000 Hz sound wave in a state in which earplug according to the second embodiment of the present disclosure is worn and in a state in which it is not worn; 
         FIG.  9    is a graph showing the results of emitting the 4000 Hz sound wave in a state in which earplug according to the second embodiment of the present disclosure is worn and in a state in which it is not worn; 
         FIG.  10    is a perspective view showing an earplug according to a third embodiment of the present disclosure; 
         FIG.  11    is a cutaway perspective view of the earplug according to the third embodiment of the present disclosure; 
         FIG.  12    is a cross-sectional view showing an earplug according to a fourth embodiment of the present disclosure; and 
         FIG.  13    is a cross-sectional view showing an earplug according to a fifth embodiment of the present disclosure. 
     
    
    
     MODE FOR INVENTION 
     While the present disclosure may be modified in various ways and take on various alternative forms, specific embodiments thereof are shown and described in detail below. However, it should be understood that there is no intent to limit the present disclosure to the particular forms disclosed, but on the contrary, the present disclosure covers all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure. 
     The terminology used herein to describe embodiments of the present disclosure is not intended to limit the scope of the present disclosure. The singular expression includes the plural expression unless the context clearly dictates otherwise. It should be further understood that the terms “comprise”, “include”, and/or “have”, when used herein, specify the presence of stated features, numbers, steps, operations, elements, components, and/or groups thereof but do not preclude the presence or addition of one or more other features, numbers, steps, operations, elements, components, and/or groups thereof. 
     Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In this case, it should be noted that in the accompanying drawings, the same components are denoted by the same reference numerals as much as possible. In addition, detailed descriptions of well-known functions and configurations that may obscure the gist of the present disclosure will be omitted. For the same reason, some components are exaggerated, omitted, or schematically illustrated in the accompanying drawings. 
     Hereinafter, a gripper having a fastening function according to a first embodiment of the present disclosure will be described. 
       FIG.  1    is a perspective view showing an earplug according to the first embodiment of the present disclosure,  FIG.  2    is a cutaway perspective view of the earplug according to the first embodiment of the present disclosure, cut in the transverse direction, and  FIG.  3    is a cutaway perspective view of the earplug according to the first embodiment of the present disclosure, cut in the longitudinal direction. 
     When described with reference to  FIGS.  1  to  3   , an earplug  101  according to the first embodiment includes an eartip  110 , an interference attenuation module  120 , and a connecting tube  130 . The earplug  101  according to the present embodiment may be made of an earplug that blocks high-frequency noise. In this description, high-frequency noise means noise between 1000 Hz and 8000 Hz. High-frequency noise is high-frequency noise generated in construction sites, factories, and dental clinics, and may cause hearing loss if exposed for a long time. Also, in this description, a metasurface is defined as an artificial surface or shape added for reflection of sound waves. 
     The eartip  110  may have a structure similar to the eartip of a general canal type earphone. The eartip  110  may be inserted inside a user&#39;s ear, in particular, the ear canal. The eartip  110  includes a tip tube  112  coupled to the connecting tube  130  and a sleeve  114  that protrudes outward from the tip tube  112  and is in close contact with the ear canal. The eartip  110  is formed to be detachable to the connecting tube  130 . 
     Meanwhile, the tip tube  112  is made of a cylindrical tube and an internal passage  115  connected to the connecting tube  130  is formed on the inside of the tip tube  112 . A low-frequency sound wave such as an unattenuated voice may be transmitted through the internal passage  115 . The sleeve  114  has an arc-shaped curved plate structure and protrudes backward from the tip tube  112 . The sleeve  114  is in close contact with the user&#39;s ear canal to prevent noise from penetrating into the ear canal. 
     The connecting tube  130  is made of a cylindrical tube and connects the eartip  110  and the interference attenuation module  120 . An intermediate passage  131  is formed inside the connecting tube  130 , and the sound wave transmitted from the interference attenuation module  120  may be transmitted to the eartip  110  through the connecting tube  130 . 
     The interference attenuation module  120  transmits sound to the connecting tube  130  and may include a damping passage  125  for reducing noise, a first damping protrusion  140  protruding in the lateral direction of the damping passage  125 , and a second damping protrusion  150  protruding in the direction crossing the first damping protrusion  140 . 
     The two first damping protrusions  140  protrude in opposite directions and are spaced apart from each other with the damping passage  125  interposed therebetween. The second damping protrusion  150  is protruded to vertically intersect with the first damping protrusion  140 , and the two second damping protrusions  150  are spaced apart from each other with the damping passage  125  interposed therebetween. The first damping protrusions  140  are arranged in a line parallel to each other, and the second damping protrusions  150  are also arranged in a line parallel to each other. Accordingly, the first damping protrusions  140  and the second damping protrusions  150  may be combined and arranged in a cross shape. 
     In addition, the first damping protrusion  140  has the same length as the second damping protrusion  150 , and the first damping protrusion  140  may protrude further rearward than the second damping protrusion  150 . In the present description, the front refers to a direction toward the front end of the eartip  110 , and the rear refers to a direction in which the interference attenuation module is located. 
     Inside the first damping protrusion  140 , a first reflective cavity  121  that is connected to the damping passage  125  and reflects the incident sound waves and transmits the sound waves to the damping passage  125  is formed. Also, inside the second damping protrusion  140 , a second reflective cavity  122  that is connected to the damping passage  125  and reflects the incident sound waves and transmits the sound waves to the damping passage  125  is formed. The two first reflective cavities  121  and the two second reflective cavities  122  may be connected in a cross shape via the damping passage  125  as a medium. The first reflective cavity  121  and the second reflective cavity  122  are artificial metasurfaces added for reflection of sound waves, and the high-frequency noise introduced into the first reflective cavity  121  and the second reflective cavity  122  is phase-shifted. 
     The damping passage  125  is positioned between the first damping protrusion  140  and the second damping protrusion  150 , and has a noise inlet (NI) that is opened to the rear and into which noise is incident. Accordingly, the earplug according to the present embodiment is of an open type through which noise may be introduced. 
     A first opening  126  connecting the first reflective cavity  121  and the damping passage  125  is formed in the first reflective cavity  121 , and a second opening  127  connecting the second reflective cavity  122  and the damping passage  125  is formed in the second reflective cavity  122 . The first opening  126  and the second opening  127  are spaced apart from each other in the longitudinal direction of the damping passage  125 , and the second opening  127  is located more forward than the first opening  126 . 
     Meanwhile, the second reflective cavity  122  has a smaller volume than the first reflective cavity  121 , and accordingly, the first reflective cavity  121  and the second reflective cavity  122  may reflect sound waves of different frequencies. The first reflective cavity  121  and the second reflective cavity  122  that are metasurfaces may be formed to reflect sound waves of a specific frequency. 
     Some of the noise introduced through the damping passage  125  is introduced into the first reflective cavity  121  through the first opening  126 , and high-frequency waves among the introduced sound waves are reflected from the first reflective cavity  121  and phase-shifted to be discharged to the damping passage  125  through the first opening  126 . 
     In addition, some of the noise introduced through the damping passage  125  is introduced into the second reflective cavity  122  through the second opening  127 , and high-frequency waves among the introduced sound waves are reflected from the second reflective cavity  122  and phase-shifted to be discharged to the damping passage  125  through the second opening  127 . 
     Sound waves reflected from the first reflective cavity  121  and the second reflective cavity  122  may interfere with high-frequency sound waves incident from the damping passage, so that destructive interference of the noise may occur. The frequency of the attenuated sound wave may be adjusted by changing the structures of the first reflective cavity  121  and the second reflective cavity  122 . 
     In general, noise generated in construction sites, factories, and dental clinics is high-frequency sound waves, and these high-frequency noises cause hearing loss. However, communication is necessary during work, so if you wear earplugs that block all sounds, communication during work is impossible, which reduces work efficiency. The earplug according to the present embodiment attenuates only high-frequency noise among noises introduced into the damping passage and passes the voice through, so that it is possible to communicate easily while preventing hearing loss. 
     Hereinafter, an earplug according to a second embodiment of the present disclosure will be described. 
       FIG.  4    is a perspective view showing the earplug according to the second embodiment of the present disclosure, and  FIG.  5    is a cross-sectional view of the earplug according to the second embodiment of the present disclosure. 
     Since the earplug  102  according to the second embodiment has the same structure as the earplug  102  according to the first embodiment except for a casing  160 , a redundant description of the same configuration will be omitted. 
     An interference attenuation module  120  transmits sound to a connecting tube  130  and may include a damping passage  125  for reducing noise, a first damping protrusion  140  protruding in the lateral direction of the damping passage  125 , a second damping protrusion  150  protruding in the direction crossing the first damping protrusion  140 , and the casing  160  surrounding the first damping protrusion  140  and the second damping protrusion  150 . 
     Inside the first damping protrusion  140 , a first reflective cavity  121  that is connected to the damping passage  125  and reflects the incident sound waves and transmits the sound waves to the damping passage  125  is formed. Also, inside the second damping protrusion  140 , a second reflective cavity  122  that is connected to the damping passage  125  and reflects the incident sound waves and transmits the sound waves to the damping passage  125  is formed. The first reflective cavity  121  and the second reflective cavity  122  may be connected in a cross shape via the damping passage  125  as a medium. 
     The casing  160  has a cylindrical shape, and a noise inlet  162  through which sound waves are introduced is formed in the casing  160 . The noise inlet  162  is formed on the outer peripheral surface of the casing  160  and is located at the rear of the second damping protrusion  150 . Meanwhile, between the casing  160  and the first damping protrusion  140  and the second damping protrusion  150 , a third reflective cavity  161  from which a sound wave is reflected is formed. 
     Accordingly, the sound waves introduced into the noise inlet  162  are reflected once from the third reflective cavity  161  and then flow into the first reflective cavity  121  and the second reflective cavity  122  through the damping passage  125 . Noise may be reduced through destructive interference in the damping passage  125 . 
       FIG.  6    is a photograph showing the simulation results of emitting a 1000 Hz sound wave to the earplug according to the second embodiment of the present disclosure, and  FIG.  7    is a photograph showing the simulation results of emitting a 4000 Hz sound wave to the earplug according to the second embodiment of the present disclosure. 
     As shown in  FIG.  6   , the 1000 Hz sound wave does not pass through the earplug  102 , and the 4000 Hz sound wave is blocked more stably by the earplug  102 . 
       FIG.  8    is a graph showing the results of emitting the 1000 Hz sound wave in a state in which earplug according to the second embodiment of the present disclosure is worn and in a state in which it is not worn, and  FIG.  9    is a graph showing the results of emitting the 4000 Hz sound wave in a state in which earplug according to the second embodiment of the present disclosure is worn and in a state in which it is not worn. 
     As shown in  FIG.  8   , when the earplug is worn, only a small change in pressure appears inside the earplug by passing only a very small volume of the 1000 Hz sound wave, and as shown in  FIG.  9   , 4000 Hz sound wave is mostly blocked by the earplug  102 , so there is little change in pressure. 
     Hereinafter, an earplug according to a third embodiment of the present disclosure will be described. 
       FIG.  10    is a perspective view showing the earplug according to the third embodiment of the present disclosure, and  FIG.  11    is a cutaway perspective view of the earplug according to the third embodiment of the present disclosure. 
     When described with reference to  FIGS.  10  and  11   , since the earplug  103  according to the third embodiment has the same structure as the earplug according to the first embodiment except for an interference attenuation module  170 , a redundant description of the same configuration will be omitted. 
     The interference attenuation module  170  transmits sound to a connecting tube and may include a damping passage  175  for reducing noise, a first damping protrusion  171  protruding in the lateral direction of the damping passage  175 . A first reflective cavity  173  is formed inside the first damping protrusion  171  that is connected to the damping passage  175  and reflects the incident sound waves and transmits the sound waves to the damping passage  175 . 
     A first opening  176  connecting the first reflective cavity  173  and the damping passage  175  is formed in the first reflective cavity  173 . The two first damping protrusions  171  protrude in opposite directions and are arranged in parallel with the damping passage  175  therebetween and are connected in a line. The damping passage  175  is positioned between the first damping protrusion  171  and the second damping protrusion, and has a noise inlet (NI) that is opened to the rear and into which noise is incident. 
     Accordingly, the sound wave introduced into the noise inlet NI is introduced into the first reflective cavity  173  and reflected, and noise may be reduced through destructive interference in the damping passage  175 . 
     Hereinafter, an earplug according to a fourth embodiment of the present disclosure will be described. 
       FIG.  12    is a cross-sectional view showing the earplug according to the fourth embodiment of the present disclosure. 
     When described with reference to  FIG.  12   , since the earplug  104  according to the present embodiment has the the same structure as the earplug according to the first embodiment except for the eartip  180 , a redundant description of the same configuration will be omitted. 
     The eartip  180  includes a tip tube  181  coupled to a connecting tube and a plurality of sleeves  182 ,  183 , and  184  that protrude outward from the tip tube  181  and are in close contact with the ear canal. The eartip  180  is formed to be detachable to the connecting tube  130 . 
     The tip tube  181  is made of a cylindrical tube and is fitted to the connecting tube  130 . An internal passage  185  connected to the connecting tube  130  is formed on the inside of the tip tube  181 , and low-frequency sound waves such as unattenuated voice may be transmitted through the internal passage  185 . 
     The sleeves  182 ,  183 , and  184  have an arc-shaped curved structure and protrude rearward from the tip tube  181 . The plurality of sleeves  182 ,  183 , and  184  may protrude from the tip tube  181 . As such, when the eartip  180  includes the plurality of sleeves  182 ,  183 , and  184 , the sleeves  182 ,  183 , and  184  are more closely attached to the ear canal, thereby preventing noise from penetrating into the ear canal. 
     Hereinafter, an earplug according to a fifth embodiment of the present disclosure will be described.  FIG.  13    is a cross-sectional view showing the earplug according to the fifth embodiment of the present disclosure. 
     When described with reference to  FIG.  13   , since the earplug  105  according to the present fifth embodiment has the same structure as the earplug according to the first embodiment except for a damping protrusion, a redundant description of the same configuration will be omitted. 
     An interference attenuation module  190  transmits sound to a connecting tube  130  and may include a damping passage  195  for reducing noise, a first damping protrusion  191  protruding in the lateral direction of the damping passage  195 , and a second damping protrusion protruding in the direction crossing the first damping protrusion  191 . 
     Inside the first damping protrusion  191 , a first reflective cavity  192  that is connected to the damping passage  195  and reflects the incident sound waves and transmits the sound waves to the damping passage is formed. Also, a second reflective cavity is formed inside the second damping protrusion. The first reflective cavity  192  and the second reflective cavity may be connected in a cross shape via the damping passage as a medium. Since the first damping protrusion  191  and the second damping protrusion have a similar structure, the description of the first damping protrusion  191  will replace the description of the second damping protrusion. 
     The first damping protrusion  191  includes a first body  193  and a second body  194  slidable to the first body  193 , and thus the volume of the first reflective cavity  192  may be increased or decreased. A first concave-convex portion  193 a is formed on the outer circumferential surface of the first body  193 , and a second concave-convex portion  194 a fitted to the first concave-convex portion  193 a may be formed on the inner circumferential surface of the second body  194 . Accordingly, the second body  194  slides in the first body  193  to change the volume of the first reflective cavity  192 , and when the volume of the first reflective cavity  192  is changed, the frequency of the attenuated sound wave may be changed. 
     In the above, an embodiment of the present disclosure has been described, however, those of ordinary skill in the art will be able to variously modify and change the present disclosure by supplementing, changing, deleting, or adding components within the scope that does not depart from the spirit of the present disclosure described in the claims, and this will also be included within the scope of the present disclosure.