Waterproof sound-transmissive cover, waterproof sound-transmissive cover member and acoustic device

1. A waterproof sound-transmissive cover comprising:

a porous film having:

(1) a water pressure resistance measured according to the JIS L1092 water penetration test method B (high pressure method) of 20 kPa or more, and air permeability measured according to the JIS L1096 method A (Frazier type method) of 3.0 cc/cm 2 ·sec or more, and

(2) a tensile strength measured according to ASTM D412 standards of 5.5N or more;

wherein an acoustic device comprising the waterproof sound-transmissive cover provides a frequency response curve with a difference between a maximum sound pressure level and a minimum sound pressure level (“sound pressure level difference”), of 13.0 dB or less in the range of frequencies from 3 kHz to 8 kHz, and

wherein an acoustic device comprising the waterproof sound-transmissive cover provides an insertion loss of less than 14.0 dB at 1 kHz.

2. The waterproof sound-transmissive cover according to claim 1 , wherein the porous film comprises a porous polytetrafluoroethylene film, wherein the porous film comprises:

a plurality of nodes and

a plurality of fibrils formed between the plurality of nodes;

wherein each of the nodes has an aspect ratio of 25 or more, wherein the aspect ratio is defined by a ratio of the length of each node to a diameter of each node.

3. The waterproof sound-transmissive cover according to claim 1 , wherein the waterproof sound-transmissive cover has a thickness in the range of 10 to 300 micrometers.

4. The waterproof sound-transmissive cover according claim 1 , wherein said water pressure resistance is 55 kPa or less.

5. The waterproof sound-transmissive cover according to claim 1 , wherein the frequency response curve provides a sound pressure level at a frequency of 8 kHz that is smaller than a sound pressure level at a frequency of 1 kHz.

6. The waterproof sound-transmissive cover according to claim 1 , wherein the frequency response curve provides:

a sound pressure difference in the range of frequencies from 3 kHz to 5 kHz of 4.0 dB or less,

and a sound pressure difference in the range of frequencies from 5 kHz to 8 kHz of 9.0 dB or less.

7. The waterproof sound-transmissive cover according to claim 1 , wherein the porous film is a single layer of the porous polytetrafluoroethylene film.

8. The waterproof sound-transmissive cover according to claim 1 , wherein the water pressure resistance of the porous film, measured according to the JIS L1092 water penetration test method B (high pressure method), is from 20 kPa to 90 kPa.

9. The waterproof sound-transmissive cover according to claim 1 , wherein the air permeability of the porous film, measured according to the JIS L1096 method A (Frazier type method) is from 3.0 cc/cm 2 ·sec to 10 cc/cm 2 ·sec.

10. The waterproof sound-transmissive cover according to claim 1 , wherein the sound pressure level difference is from 3.0 dB to 13.0 dB in the range of frequencies from 3 kHz to 8 kHz.

11. The waterproof sound-transmissive cover according to claim 1 , wherein an acoustic device comprising the waterproof sound-transmissive cover provides an insertion loss of 5.0 dB to 14.0 dB at 1 kHz.

12. A waterproof sound-transmissive cover member comprising:

(A) a waterproof sound-transmissive cover comprising a porous film having:

(1) a water pressure resistance measured according to the JIS L1092 water penetration test method B (high pressure method) of 20 kPa or more, and air permeability measured according to the JIS L1096 method A (Frazier type method) of 3.0 cc/cm 2 sec or more, and

(2) a tensile strength measured according to ASTM D412 standards of 5.5N or more; and

(B) a support layer formed on at least one side of the waterproof sound-transmissive cover

wherein an acoustic device comprising the waterproof sound-transmissive cover member provides a frequency response curve with a difference between a maximum sound pressure level and a minimum sound pressure level (“sound pressure level difference”), of 13.0 dB or less in the range of frequencies from 3 kHz to 8 kHz, and

wherein an acoustic device comprising the waterproof sound-transmissive cover member provides an insertion loss of less than 14.0 dB at 1 kHz.

13. An acoustic device, comprising:

(A) a housing having an opening configured to pass an acoustic wave therethrough;

(B) an acoustoelectric converter disposed inside of the housing; and

(C) a waterproof sound-transmissive cover member, comprising:

(1) a waterproof sound-transmissive cover comprising a porous film having:

(I) water pressure resistance measured according to the JIS L1092 water penetration test method B (high pressure method) of 20 kPa or more, and air permeability measured according to the JIS L1096 method A (Frazier type method) of 3.0 cc/cm 2 ·sec or more, and

(II) a tensile strength measured according to ASTM D412 standards of 5.5N or more; and

(2) a support layer formed on at least one side of the waterproof sound-transmissive cover

wherein the waterproof sound-transmissive cover member covers the opening of the housing,

wherein the acoustic device provides a frequency response curve with a difference between a maximum sound pressure level and a minimum sound pressure level (“sound pressure level difference”), of 13.0 dB or less in the range of frequencies from 3 kHz to 8 kHz, and

wherein the acoustic device provides an insertion loss of less than 14.0 dB at 1 kHz.

14. The acoustic device of claim 13 , wherein the device is configured to send an acoustic wave.

15. The acoustic device of claim 13 , wherein the device is configured to receive an acoustic wave.

16. The acoustic device of claim 13 , wherein the device is configured to send and receive an acoustic wave.