Waterproof sound-transmitting member
A waterproof sound-transmitting member includes a waterproof sound-transmitting membrane and a support layer. The support layer includes a polyolefin-based resin foam. The support layer has a loss modulus of 1.0×10 7 Pa or less and a loss factor of 1.0×10 −1 or more. The waterproof sound-transmitting membrane is, for example, a stretched porous polytetrafluoroethylene membrane. The waterproof sound-transmitting membrane may include an adhesive layer.
1. A waterproof sound-transmitting member comprising:
a waterproof sound-transmitting membrane; and
a support layer joined to at least one surface of the waterproof sound-transmitting membrane,
wherein the support layer comprises a polyolefin-based resin foam, and
the support layer has a loss modulus of 1.0×10 7 Pa or less and a loss factor of 1.0×10 −1 or more.
2. The waterproof sound-transmitting member according to claim 1 ,
wherein the support layer has an opening, and
when a shortest line segment passing through a center of gravity of the opening and connecting two points on an inner periphery of the support layer surrounding the opening is defined as a first line segment and a line segment passing through the center of gravity of the opening, perpendicular to the first line segment, and connecting two points on the inner periphery of the support layer surrounding the opening is defined as a second line segment, the second line segment has a length at least twice a length of the first line segment.
3. The waterproof sound-transmitting member according to claim 2 ,
wherein the inner periphery of the support layer surrounding the opening defines a rectangular region having first sides parallel to the first line segment and second sides parallel to the second line segment.
4. The waterproof sound-transmitting member according to claim 1 ,
wherein an outer periphery of the support layer coincides with an outer periphery of the waterproof sound-transmitting membrane, as viewed in a direction in which sound is transmitted.
5. The waterproof sound-transmitting member according to claim 1 ,
wherein the waterproof sound-transmitting membrane is a stretched porous polytetrafluoroethylene membrane.
6. The waterproof sound-transmitting member according to claim 1 ,
wherein the support layer has a storage modulus of 1.49×10 7 Pa or more and 2.16×10 7 Pa or less,
the support layer has the loss modulus of 2.09×10 6 Pa or more and 2.83×10 6 Pa or less, and
the support layer has the loss factor of 1.23×10 −1 or more and 1.46×10 −1 or less.
7. The waterproof sound-transmitting member according to claim 1 ,
wherein the polyolefin-based resin foam is a foam comprising, as a resin component, a mixture of a polyolefin resin and an elastomer component, and
the elastomer component is rubber or thermoplastic elastomer.