JP4294754B2 - Active noise reduction headset - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to active noise reduction.
[0002]
[Prior art]
U.S. Pat. Nos. 4,644,581, 4,922,542 and 5,305,387 are incorporated as technical background.
[0003]
[Problems to be solved by the invention]
An important object of the present invention is to provide an improved active noise reduction headphone.
[0004]
[Means for Solving the Problems]
In accordance with the present invention, a module suitable for use in an active noise reduction headset includes an enclosure having walls. A driver is attached to a part of the wall. A port interconnects the interior and exterior of the enclosure. A damper is coupled to the port.
[0005]
In another aspect of the invention, the active noise reduction headset includes an earcup that surrounds the first and second cavities separated by a divider. The headset also includes a more comfortable sealing pad. A driver with a diaphragm is mounted in the split and emits sound waves into the first cavity, which attenuates ambient noise. The port interconnects the second cavity and the exterior of the enclosure.
[0006]
Other features, objects and advantages will become apparent from the following detailed description when taken in conjunction with the accompanying drawings.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings and more particularly to FIG. 1, an active noise reduction headset according to the present invention is shown. A headband 56 is attached to the two earcup structures 58. Each of the earcup structures 58 includes an earcup portion 50 and a comfort pad 54. The headband can be one of many types, including a headband in which the length of the headband or the position of the earcup structure on the headband is adjustable. The connection between the headband 56 and the earcup structure allows for adjustment along one or more axes relative to the headband. In use, the headband 56 holds the ear cup structure 58 so as to cover the user's ear and surrounds the ear (circumaural) or covers the ear (supraural).
[0008]
Referring to FIGS. 2-4, schematic cross-sectional views of the earcup structure 58 are shown. In FIG. 2, the ear cup shell 50 surrounds the front cavity 52. The comfort pads 54 adhere to the side of the user's head so that they seal the user's ears from most of the ambient noise. The front cavity 52 surrounds the active noise reduction module 10. The active noise reduction module 10 includes a driver 18 with a sound radiation diaphragm 21. Port 16 and acoustic resistance opening 17 extend through ear cup shell 50 in parallel. These will be described in more detail below. 3 and 4, a passage 19 connects the port and resistance opening 17 to the surrounding environment. The size of the passage 19 is such that the passage does not act as a port or a waveguide of sound waves emitted from the diaphragm 21. The acoustic effect is the same as when both port 16 and resistive opening 17 are directly connected to the surrounding environment as in FIG. A damping material 53 (eg, open cell foam) may be disposed in the front cavity 52 to reduce resonance in the front cavity and assist in passive damping. The embodiment as in FIGS. 3 and 4 allows for a flexible arrangement of the active noise reduction module, minimizes modifications to the ear cup, and provides an active noise reduction module for a variety of different ear cups. There is an advantage that 10 can be implemented.
[0009]
In operation, the microphone 22 measures the sound pressure. A circuit (not shown) compares the sound pressure measured by the microphone 22 with the sound pressure due to the sound waves emitted by the diaphragm 21, detects ambient noise, and transmits a signal to the driver 18, similar to ambient noise. However, the ambient noise is greatly attenuated by causing the diaphragm 21 to emit an acoustic pattern out of phase with the ambient noise.
[0010]
Referring to FIGS. 5A-5B, an active noise reduction module 10 is illustrated. Enclosure 12 surrounds rear cavity 14 (A in FIG. 6 through D in FIG. 6). Port 16 and acoustic resistance opening 17 extend through the wall of enclosure 12. A driver 18 is attached to the surface of the enclosure 12. A microphone 22 is attached to the outer surface of the enclosure 12. In the present embodiment, the microphone 22 is attached at a position near the end of the diaphragm 21, and the pickup surface faces inward in the radial direction. That is, the straight line perpendicular to the pickup surface is attached so as to be substantially orthogonal to the shaft 24 of the driver 18.
[0011]
In one embodiment of the present invention, the enclosure 12 is generally cylindrical and the driver 18 has a diameter of about 42 mm and is attached to one of the planes of the cylinder. The rear cavity 14 surrounded by the enclosure 12 typically has a volume of about 10 to 20 cubic centimeters, and the front cavity 52 typically has a volume of about 100 to 200 cubic centimeters. The acoustic mass of the port 16 and the compliance of the back cavity 14 are typically tuned to a frequency of about 300 Hz. The acoustic resistance aperture 16 provides an acoustic resistance of about 1 × 16 ⁷ ohms. The resistance opening 17 may be an opening 17a having an acoustic resistance coating 17b, or may be an opening filled with an acoustic resistance substance.
[0012]
Referring now to FIGS. 6A-6D, an active noise reduction module 10 is shown. In these figures, certain elements have been omitted or changed to better explain the invention. Several effects of the embodiment of FIG. 6A will be described below with reference to FIGS. 6B to 6D. In FIG. 6B, the port 16 and the resistance opening 17 are omitted. In FIG. 6C, the resistance opening 17 is omitted. In FIG. 6D, the resistance opening 17 is omitted, and the acoustic resistance material 16 a is inserted into the port 16. (Alternatively, the opening of port 16 may be coated with an acoustic resistance material).
[0013]
In the embodiment of FIG. 6D, the acoustic resistance of the acoustic material 16 a connects the back cavity 14 in communication with the surrounding environment in series with the mass of air in the port 16. In the embodiment of FIG. 6A, the acoustic resistance of the resistive opening 18 connects the back cavity 14 leading to the ambient environment in parallel with the mass of air in the port 16.
[0014]
Referring now to FIG. 7, a graph of a computer simulation in which the response of driver 18 as a function of frequency is shown, representing the effect of the various elements of the embodiment of FIG. Curve 24 represents the response of driver 18 in the embodiment of FIG. Curve 26 represents the response of driver 18 in the embodiment shown in FIG. Compared to curve 24, curve 26 not only shows a better response at low frequencies, but in this case has a low output at a port resonant frequency of 300 Hz. Curve 28 represents the response of driver 18 in the embodiment shown in FIG. Compared to curve 26, curve 28 shows a smoother frequency response and an improved response at low frequencies. Curve 30 represents the response of the embodiment of FIG. Compared to curves 24, 26 and 28, curve 30 shows a smooth frequency response and an improved response at low frequencies.
[0015]
The ear cup according to the present invention is more advantageous than the conventional ear cup because the structure of the port and the resistive path enables active damping and the rear cavity can be greatly reduced. This feature also provides a given earcup size, an increase in the front cavity and improves passive damping. The smooth frequency response makes it easy to combine simplified driver circuitry with greater efficiency in driver operation, which can be a significant advantage in battery powered active noise reduction headsets Make it possible.
[0016]
Other embodiments are within the scope of the claims.
[Brief description of the drawings]
FIG. 1 is a plan view of a noise reduction headset.
FIG. 2 is a schematic cross-sectional view of an earcup that embodies the present invention.
FIG. 3 is a schematic cross-sectional view of an earcup that embodies the present invention.
FIG. 4 is a schematic cross-sectional view of an ear cup embodying the present invention.
FIG. 5 is a perspective view of a module according to the present invention.
FIG. 6 is a cross-sectional view showing another embodiment of a module according to the present invention.
7 is a graph showing the relationship between driver response and frequency for the modules of FIGS. 6A to 6D. FIG.
[Explanation of symbols]
10 Active Noise Reduction Module 12 Enclosure 14 Rear Cavity 14
16 Port 17 Acoustic resistance opening 18 Driver 19 Passage 21 Sound wave radiating diaphragm 22 Microphone 50 Ear cup portion (ear cup shell)
52 Front cavity 53 Damping material 54 Comfort pad 56 Headband 58 Ear cup structure

Claims (9)

Comprising an ear cup surrounding the compliant rear and front cavities and arranged to seal from the side of the user's head ;
The volume of the rear cavity is smaller than 1/5 of the volume of the front cavity,
The front cavity opens towards the user's ear;
A dividing part separating the front cavity and the rear cavity;
A driver attached to the divider and cooperating with it to attach a diaphragm to prevent air flow between the front cavity and the rear cavity;
A port connecting the rear cavity and the outside of the ear cup,
The port has a mass that cooperates with the compliance to form a resonant circuit that resonates at a resonant frequency;
An active noise reduction headset comprising an acoustic resistive aperture that communicates the rear cavity and the exterior in parallel with the port. 2. The active noise reduction headset according to claim 1, further comprising a microphone having a pickup surface, wherein the microphone is attached in the vicinity of an outer edge of the diaphragm. 3. The active noise reduction headset according to claim 2, wherein the pickup surface of the microphone is oriented perpendicular to the axis of the driver. 3. The active noise reduction headset according to claim 2, wherein a pickup surface of the microphone faces a radially inner side of the diaphragm. In claim 1 headset according, has a volume of the rear cavity of about 10～20Cc, active noise reduction headset having a volume of said front cavity about 100～200Cc. An active noise reduction headset,
An ear cup surrounding the first cavity and the second cavity having compliance;
The volume of the second cavity is less than 1/5 of the volume of the first cavity,
The first cavity and the second cavity are separated by a dividing portion;
A comfort pad constructed and arranged to seal the ear cup from the side of the user's head;
A driver attached to the dividing portion and cooperating with it to attach a diaphragm for preventing an air flow between the first cavity and the second cavity;
A port communicating the second cavity with an outer region of the earcup,
The port has a mass that cooperates with the compliance of the second cavity to form a resonant circuit;
An active noise reduction headset comprising an acoustic resistive opening that communicates the second cavity and the outer region of the earcup in parallel with the port. A headset according to claim 6, further wherein the first active noise reduction headset includes a microphone into the cavity. 8. The active noise reduction headset according to claim 7, wherein the microphone is attached in the vicinity of an outer edge of the diaphragm. The headset of claim 6,
The division part includes a module wall part,
The module surrounds the second cavity;
The module is adapted to be detachably integrated within the earcup such that the port and the acoustically resistive opening communicate the second cavity and the region through the opening of the earcup. Active noise reduction headset.

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