Abstract: A waterproof sound-transmitting membrane (10) includes a sound-transmitting region (13c) having a porous polytetrafluoroethylene (PTFE) membrane (11). The porous PTFE membrane (11) has a through-thickness air permeability of 2 cm3/cm2/s or more. Thus, it is possible to provide a waterproof sound-transmitting membrane that is suitable for reducing crackling noise while ensuring waterproofness required for at least daily use. The porous PTFE membrane (11) has a water entry pressure of 3 kPa or more, preferably 20 kPa or more and 50 kPa or less. The waterproof sound-transmitting membrane (10) may include an edge region (13p) having an adhesive layer (12).

Abstract: A waterproof sound-transmitting membrane (10) includes a sound-transmitting region (13c) having a porous polytetrafluoroethylene (PTFE) membrane (11). The porous PTFE membrane (11) has a through-thickness air permeability of 2 cm3/cm2/s or more. Thus, it is possible to provide a waterproof sound-transmitting membrane that is suitable for reducing crackling noise while ensuring waterproofness required for at least daily use. The porous PTFE membrane (11) has a water entry pressure of 3 kPa or more, preferably 20 kPa or more and 50 kPa or less. The waterproof sound-transmitting membrane (10) may include an edge region (13p) having an adhesive layer (12).

Abstract: The present invention provides a sound-transmitting membrane for a microphone, to be disposed to a sound-collecting opening of the microphone so as to allow sound to transmit through the membrane while preventing a foreign matter from entering into the microphone through the opening. This membrane for a microphone prevents the entry of a foreign matter, such as fine dust and water vapor, that is difficult for conventional sound-transmitting membranes to block, and ensures the microphone performance. This membrane for a microphone is composed of a nonporous film or a multilayer membrane including a nonporous film, has a surface density of 30 g/m2 or less, and has a sound transmission loss of less than 3 dB in a frequency range of 300 to 4000 Hz.

Abstract: The present invention provides a water-proof sound-transmitting membrane including a polytetrafluoroethylene (PTFE) porous membrane, in which the waterproofness is enhanced further with little lowering of the sound transmittance. The water-proof sound-transmitting membrane includes the PTFE porous membrane. The PTFE porous membrane includes a first porous layer, and a second porous layer stacked on and integrated with the first porous layer by a binding force acting between PTFE matrices. The first porous layer and the second porous layer each are composed of PTFE with a number-average molecular weight of 5.0×107 or more determined by a standard specific gravity method. At least one layer selected from the first porous layer and the second porous layer has an average pore diameter of 1 ?m or less. The water-proof sound-transmitting membrane has a surface density of 1 g/m2 to 10 g/m2.

Abstract: First, a mixture of a polytetrafluoroethylene fine powder and a liquid lubricant into a sheet-form body extending in a first direction. Next, the liquid lubricant is removed from the sheet-form body. Then, the sheet-form body is stretched by a factor of 40 to 250 in the longitudinal direction at a temperature equal to or higher than a melting point of polytetrafluoroethylene, and the stretched sheet-form body is further stretched by a factor of 3 to 40 in the width direction. Thus, a highly air-permeable porous polytetrafluoroethylene membrane is obtained.

Abstract: The present invention provides a sound-transmitting membrane for a microphone, to be disposed to a sound-collecting opening of the microphone so as to allow sound to transmit through the membrane while preventing a foreign matter from entering into the microphone through the opening. This membrane for a microphone prevents the entry of a foreign matter, such as fine dust and water vapor, that is difficult for conventional sound-transmitting membranes to block, and ensures the microphone performance. This membrane for a microphone is composed of a nonporous film or a multilayer membrane including a nonporous film, has a surface density of 30 g/m2 or less, and has a sound transmission loss of less than 3 dB in a frequency range of 300 to 4000 Hz.

Abstract: The present invention provides a water-proof sound-transmitting membrane including a polytetrafluoroethylene (PTFE) porous membrane, in which the waterproofness is enhanced further with little lowering of the sound transmittance. The water-proof sound-transmitting membrane includes the PTFE porous membrane. The PTFE porous membrane includes a first porous layer, and a second porous layer stacked on and integrated with the first porous layer by a binding force acting between PTFE matrices. The first porous layer and the second porous layer each are composed of PTFE with a number-average molecular weight of 5.0×107 or more determined by a standard specific gravity method. At least one layer selected from the first porous layer and the second porous layer has an average pore diameter of 1 ?m or less. The water-proof sound-transmitting membrane has a surface density of 1 g/m2 to 10 g/m2.

Abstract: First, a mixture of a polytetrafluoroethylene fine powder and a liquid lubricant into a sheet-form body extending in a first direction. Next, the liquid lubricant is removed from the sheet-form body. Then, the sheet-form body is stretched by a factor of 40 to 250 in the longitudinal direction at a temperature equal to or higher than a melting point of polytetrafluoroethylene, and the stretched sheet-form body is further stretched by a factor of 3 to 40 in the width direction. Thus, a highly air-permeable porous polytetrafluoroethylene membrane is obtained.