Acoustic sensor and acoustic sensor system

Abstract

According to one embodiment, an acoustic sensor includes a base and a first strain sensing element. The base includes a support and a first film unit supported by the support. The first film unit is flexible. The first strain sensing element is provided on a first surface of the first film unit. The first strain sensing element includes a first magnetic layer, a second magnetic layer, and a first intermediate layer provided between the first magnetic layer and the second magnetic layer. An angle between a magnetization of the first magnetic layer and a magnetization of the second magnetic layer is variable by an acoustic wave. The acoustic wave is transmitted to a first film unit by a first transmitting material in contact with the first film unit.

1 - 20 . (canceled) 
     
     
         21 . An acoustic sensor comprising:
 a base including a support and a first film supported by the support, the first film being flexible;   a first strain sensing element provided on a first surface of the first film, the first strain sensing element including a first magnetic layer, a second magnetic layer, and a first intermediate layer provided between the first magnetic layer and the second magnetic layer;   a first member; and   a second member being provided between the first member and the first film,   a first acoustic impedance of the first member being higher than a second acoustic impedance of the second member.   
     
     
         22 . The acoustic sensor according to  claim 21 , wherein the second member contacts the first member. 
     
     
         23 . The acoustic sensor according to  claim 21 , wherein an electric resistance between the first magnetic layer and the second magnetic layer is variable in accordance with an acoustic wave received by the first member. 
     
     
         24 . The acoustic sensor according to  claim 21 , wherein the second member is disposed in a space partitioned by the support and the first film. 
     
     
         25 . The acoustic sensor according to  claim 21 , wherein
 the first layer includes a solid, and   the second layer includes at least one of a liquid and a gel.   
     
     
         26 . The acoustic sensor according to  claim 21 , further comprising a third member provided between the first member and the second member,
 a third acoustic impedance of the third member is between the first acoustic impedance and the second acoustic impedance.   
     
     
         27 . The acoustic sensor according to  claim 26 , wherein the second member includes at least one of an epoxy-based adhesive, wax, grease, and a silicone compound. 
     
     
         28 . The acoustic sensor according to  claim 26 , further comprising:
 a housing,   wherein the base, the first strain sensing element, the second member and the third member are provided in the housing.   
     
     
         29 . The acoustic sensor according to  claim 21 , wherein the second member includes at least one of a liquid, a gel, and a solid. 
     
     
         30 . The acoustic sensor according to  claim 21 , wherein the second member includes at least one of water, glycerin, mercury, and rubber. 
     
     
         31 . The acoustic sensor according to  claim 21 , further comprising:
 a second strain sensing element;   the base further including a second film supported by the support,   the second strain sensing element being provided on a second surface of the second film, the second strain sensing element including a third magnetic layer, a fourth magnetic layer, and a second intermediate layer provided between the third magnetic layer and the fourth magnetic layer;   a third member; and   a fourth member being provided between the third member and the second film,   a third acoustic impedance of the third member being higher than a fourth acoustic impedance of the fourth member.   
     
     
         32 . The acoustic sensor according to  claim 31 , wherein an area of the first surface is different from an area of the second surface. 
     
     
         33 . The acoustic sensor according to  claim 31 , wherein a resonance frequency of the first film is different from a resonance frequency of the second film. 
     
     
         34 . An acoustic sensor system comprising the acoustic sensor according to  claim 21  provided in a plurality. 
     
     
         35 . An acoustic sensor comprising:
 a base including a support and a first film supported by the support, the first film being flexible;   a first strain sensing element provided on a first surface of the first film, the first strain sensing element including a first magnetic layer, a second magnetic layer, and a first intermediate layer provided between the first magnetic layer and the second magnetic layer;   a first member including a solid; and   a second member being provided between the first member and the first film, the second member contacting the first film, the second layer including at least one of a liquid and a gel.   
     
     
         36 . The acoustic sensor according to  claim 35 , wherein the second member directly contacts the first member. 
     
     
         37 . he acoustic sensor according to  claim 35 , wherein an electric resistance between the first magnetic layer and the second magnetic layer is variable in accordance with an acoustic wave received by the first member. 
     
     
         38 . An acoustic sensor comprising:
 a base including a support and a first film supported by the support, the first film being flexible;   a first strain sensing element provided on a first surface of the first film, the first strain sensing element including a first magnetic layer, a second magnetic layer, and a first intermediate layer provided between the first magnetic layer and the second magnetic layer;   a first member including a gel; and   a second member being provided between the first member and the first film, the second member contacting the first film, the second layer including a liquid.   
     
     
         39 . The acoustic sensor according to  claim 38 , wherein the second member directly contacts the first member. 
     
     
         40 . The acoustic sensor according to  claim 38 , wherein an electric resistance between the first magnetic layer and the second magnetic layer is variable in accordance with an acoustic wave received by the first member.