In-ear active noise reduction earphone
An active noise reduction earphone. The earphone includes structure for positioning and retaining the earphone in the ear of a user without a headband, active noise reduction circuitry including an acoustic driver with a nominal diameter greater than 10 mm oriented so that a line parallel to, or coincident with, an axis of the acoustic driver and that intersects a centerline of the nozzle intersects the centerline of the nozzle at angle θ>±30 degrees. A microphone is positioned adjacent an edge of the acoustic driver. The earphone is configured so that a portion of the acoustic driver is within the concha of a user and another portion of the acoustic driver is outside the concha of the user when the earphone is in position. An opening coupling the nozzle to the environment includes impedance providing structure in the opening.
1. Apparatus, comprising:
an active noise reduction (ANR) earphone, comprising:
ANR circuitry comprising
a feedback microphone acoustically coupled to an ear canal of a user, for detecting noise;
feedback circuitry, responsive to the feedback microphone, for providing a feedback noise cancelling audio signal; and
an acoustic driver for transducing an output noise canceling audio signal comprising the feedback noise reduction audio signal;
a passageway acoustically coupling the acoustic driver and an ear canal of a user;
wherein the acoustic driver is oriented so that a line parallel to, or coincident with, an axis of the acoustic driver and that intersects a centerline of the passageway intersects the centerline of the passageway at angle θ>±30 degrees and wherein the microphone is radially positioned between a point of attachment of a voice coil to an acoustic driver diaphragm and an edge of the acoustic driver diaphragm; and
wherein the passageway has a ratio
l
A
of
1000
m
m
2
or less, where A is the open cross sectional area of the passageway and l is the length of the passageway;
wherein the passageway acoustically seals with the ear canal at the transition between the bowl of the concha and the entrance to the ear canal to form a cavity;
wherein the acoustic mass M of the passageway is
1200
kg
m
4
or less, where
M
=
ρ
l
A
,
ρ is the density of air, A is the open cross sectional area of the passageway and l is the length of the passageway; and
wherein the absolute value of the mass impedance |z| of the passageway is
800
×
10
3
kg
m
4
sec
or less at 100 Hz and
8.0
×
10
6
kg
m
4
sec
or less at 1 kHz, where |z|=Mf, where
M
=
ρ
l
A
,
ρ is the density of air, A is the open cross sectional area of the passageway and l is the length of the passageway.
2. The apparatus of claim 1 , further comprising structure engaging the outer ear for positioning and retaining the earphone in the ear.
3. The apparatus of claim 1 , wherein θ>±45 degrees.
4. The apparatus of claim 1 , further comprising an opening coupling the cavity to the environment; and
impedance-providing structure in the opening.
5. The apparatus of claim 4 , wherein the impedance-providing structure comprises an acoustically resistive material in the opening.
6. The apparatus of claim 5 , wherein the acoustically resistive material is wire mesh.
7. The apparatus of claim 5 , wherein the acoustically resistive material comprises a plastic member with holes therethrough.
8. The apparatus of claim 4 , wherein the impedance-providing structure comprises a tube acoustically coupling the opening and the environment.
9. The apparatus of claim 8 , wherein the tube is filled with foam.
10. The apparatus of claim 1 , wherein the acoustic driver has a nominal diameter of greater than 10 mm.
11. The apparatus of claim 10 , where the acoustic driver has a nominal diameter of greater than 14 mm.
12. The apparatus of claim 2 , wherein the earphone is configured so that a portion of the acoustic driver is within the concha of a user and another portion of the acoustic driver is outside the concha of the user when the earphone is in position.
13. The apparatus of claim 1 , further comprising:
a feed forward microphone, for detecting noise outside the earphone;
feed forward circuitry, responsive to the feed forward microphone, for providing a feed forward noise canceling audio signal; and
circuitry for combining the feedback noise canceling audio signal and the feed forward noise canceling audio signal to provide the output noise canceling audio signal.
14. The apparatus of claim 1 , wherein the density of air ρ is assumed to be
1.2
kg
m
3
.
15. Apparatus, comprising:
an active noise reduction (ANR) earphone, comprising:
structure for engaging the outer ear so that the earphone is positioned and retained in the ear of a user;
active noise reduction circuitry comprising
a feedback microphone acoustically coupled to an ear canal of a user, for detecting noise in the earphone;
feedback circuitry responsive to the feedback microphone for providing a feedback noise canceling audio signal; and
an acoustic driver with a nominal diameter greater than 10 mm for transducing an output noise canceling audio signal comprising the feedback noise canceling audio signal to noise canceling acoustic energy; and
the apparatus further comprising a passageway acoustically coupling the acoustic driver and an ear canal of a user, wherein the passageway has a mass impedance |z| of
8.0
×
10
6
kg
m
4
sec
or less at 1 kHz, where |z|=Mf, where
M
=
ρ
l
A
,
ρ is the density of air, A is the open cross sectional area of the passageway and l is the length of the passageway.
16. The apparatus of claim 15 , where the absolute value of the mass impedance |z| of the passageway is
800
×
10
3
kg
m
4
sec
or less at 100 Hz.
17. The apparatus of claim 15 , wherein the density of air ρ is assumed to be
1.2
kg
m
3
.
18. Apparatus, comprising:
an active noise reduction (ANR) earphone, comprising:
structure for engaging the outer ear so that the earphone is positioned and retained in the ear of a user;
active noise reduction circuitry comprising
a feedback microphone acoustically coupled to an ear canal of a user, for detecting noise in the earphone;
feedback circuitry responsive to the feedback microphone for providing a feedback noise canceling audio signal; and
an acoustic driver with a nominal diameter greater than 10 mm for transducing an output noise canceling audio signal comprising the feedback noise canceling audio signal to noise canceling acoustic energy; and
the apparatus further comprising a passageway acoustically coupling the acoustic driver and an ear canal of a user, wherein the passageway has an acoustic mass
M
of
1200
kg
m
4
or less, where
M
=
ρ
l
A
,
ρ is the density of air, A is the open cross sectional area of the passageway and l is the length of the passageway.
19. The apparatus of claim 18 , wherein the density of air ρ is assumed to be
1.2
kg
m
3
.
20. The apparatus of claim 18 , wherein the passageway has an acoustic mass
M
of
1100
kg
m
4
or less, where
M
=
ρ
l
A
,
ρ is the density of air, A is the open cross sectional area of the passageway and l is the length of the passageway.