Pressure equalization in earphones
An earphone includes an acoustic transducer and a housing that includes a first acoustic chamber acoustically coupled to a first side of the acoustic transducer and a second acoustical chamber acoustically coupled to a second side of the acoustic transducer. The housing further includes a port acoustically coupling the first acoustic chamber and the second acoustic chamber. Acoustic resistive material is positioned proximate the port.
1. An earphone comprising:
an acoustic transducer;
a housing comprising:
a first acoustic chamber acoustically coupled to a first side of the acoustic transducer;
a second acoustic chamber acoustically coupled to a second side of the acoustic transducer; and
a port acoustically coupling the first acoustic chamber and the second acoustic chamber, wherein the port has a cross-sectional area that ranges from about 0.4×10 −6 m 2 to about 40×10 −6 m 2 ; and
acoustic resistive material positioned inside of the port,
wherein a combination of the position of the acoustic resistive material and the cross-sectional area of the port causes a frequency response of the earphone to be substantially linear at low frequencies.
2. The earphone of claim 1 , wherein a length of the port ranges from about 0.1 millimeters to about 10 millimeters.
3. The earphone of claim 1 , wherein the acoustic resistive material has an impedance that ranges from about 10 MKS Rayls to about 20,000 MKS Rayls.
4. The earphone of claim 1 , wherein the acoustic resistive material comprises at least one of: a plastic, a textile, a metal, a permeable material, a woven material, a screen material, and a mesh material.
5. The earphone of claim 1 , wherein active noise cancellation circuitry is coupled to the housing via a wire.
6. The earphone of claim 1 , wherein the first acoustic chamber is separated from the second acoustic chamber by the acoustic transducer.
7. The earphone of claim 1 , wherein a frequency response of the earphone is approximately the same at high and low signal values at frequencies below 100 Hz.
8. The earphone of claim 1 , wherein a difference in a frequency response of the earphone at low signal values and a frequency response of the earphone at high signal values is less than 3 dB at frequencies between 10 and 100 Hz.
9. The earphone of claim 1 , wherein the port provides damping in a frequency response of the acoustic transducer at high frequencies.
10. The earphone of claim 1 , wherein the port has a resistive component of acoustic impedance of between about 2×10 6 acoustic ohms and about 8×10 7 acoustic ohms at low frequencies.
11. An apparatus comprising:
an acoustic transducer;
active noise cancellation circuitry;
a housing comprising:
a first acoustic chamber at least partially enclosing the acoustic transducer; and
a port proximate the first acoustic chamber, wherein the port has acoustic resistive material positioned inside the port and has a cross-sectional area that ranges from about 0.4×10 −6 m 2 to about 40×10 −6 m 2 , and wherein a combination of the position of the acoustic resistive material and the cross-sectional area of the port causes a frequency response of the earphone to be approximately the same at high and low signal values at frequencies below 100 Hz.
12. The apparatus of claim 11 , wherein the port acoustically couples the first acoustic chamber to an environment external to the earphone.
13. The apparatus of claim 11 , wherein the port acoustically couples the first acoustic chamber to a second acoustic chamber.
14. The apparatus of claim 11 , wherein a length of the port ranges from about 0.1 millimeters to about 10 millimeters.
15. The apparatus of claim 11 , wherein the acoustic resistive material has an impedance that ranges from about 10 MKS Rayls to about 20,000 MKS Rayls.
16. The apparatus of claim 11 , wherein the acoustic resistive material comprises at least one of: a plastic, a textile, a metal, a permeable material, a woven material, a screen material, and a mesh material.
17. The apparatus of claim 11 , wherein a frequency response of the earphone is substantially linear at low frequencies.
18. The apparatus of claim 11 , wherein a difference in a frequency response of the earphone at low signal values and a frequency response of the earphone at high signal values is less than 3 dB at frequencies between 10 and 100 Hz.
19. The apparatus of claim 11 , wherein the port provides damping in a frequency response of the acoustic transducer at high frequencies.
20. The apparatus of claim 11 , further comprising a resistive port.
21. The apparatus of claim 11 , wherein the port has a resistive component of acoustic impedance of between about 2×10 6 acoustic ohms and about 8×10 7 acoustic ohms at low frequencies.
22. The apparatus of claim 21 , wherein the port has a resistive component of acoustic impedance of between about 2×10 6 acoustic ohms and about 8×10 7 acoustic ohms at low frequencies.
23. An earphone comprising:
an acoustic transducer;
a housing comprising:
a first acoustic chamber acoustically coupled to a first side of the acoustic transducer;
a second acoustic chamber acoustically coupled to a second side of the acoustic transducer; and
a port acoustically coupling the first acoustic chamber and the second acoustic chamber, wherein the port has a cross-sectional area that ranges from about 0.4×10 −6 m 2 to about 40×10 −6 m 2 ; and
acoustic resistive material positioned inside of the port,
wherein a combination of the position of the acoustic resistive material and the cross-sectional area of the port causes a difference in a frequency response of the earphone at low signal values and a frequency response of the earphone at high signal values to be less than 3 dB at frequencies between 10 and 100 Hz.