# US 2014/0190765 A1 · Device for reducing the noise emitted by a conduit and aircraft conduit equipped with such a device

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- Number: US 2014/0190765 A1
- Document ID: US20140190765A1
- Status: Published application
- Kind: A1
- Application number: 14/148,520
- Filed: 2014-01-06
- Published: 2014-07-10
- Earliest claimed: 2013-01-07
- Assignees: Dassault Aviation
- Applicants: Dassault Aviation
- Inventors: Sébastien BARRÉ
- Web page: https://patentgrep.com/patent/US20140190765A1

## CPC

- B64C 1/40: Sound or heat insulation {, e.g. using insulation blankets}
- B64D 13/00: Arrangements or adaptations of air-treatment apparatus for aircraft crew or passengers, or freight space
- F04B 39/0055: {with a special shape of fluid passage, e.g. bends, throttles, diameter changes, pipes}
- F04B 49/06: Control using electricity (regulating by means of floats actuating electric switches F04B49/04)
- F16L 55/02763: {using an element with multiple tubes}
- F16L 55/0336: {by means of sound-absorbing materials}
- B64D 41/00: Power installations for auxiliary purposes
- B64D 2033/0206: {comprising noise reduction means, e.g. acoustic liners}
- B64C: AEROPLANES; HELICOPTERS
- B64D: EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
- F04B: POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS (machines for liquids, or pumps, of rotary-piston or oscillating-piston type F04C; non-positive-displacement pumps F04D; pumping of fluid by direct contact of another fluid or by using inertia of fluid to be pumped F04F)
- F16L: PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL

## Abstract

The invention relates to a device for reducing the noise emitted by a conduit belonging to an aircraft system that comprises an acoustic grid positioned in a segment of the conduit. Said grid has a length L1, along the axis (X-X) of said segment, and includes multiple meshes, each of which fits into a square with side m, the following relationships being satisfied: L1>1.8λfmin, m<λfmax/2, where fmax is the maximum frequency of the noise to be attenuated, fmin is the minimum frequency of the nice to be attenuated, λfmax is the wavelength of the noise at frequency fmax, and λfmin is the wavelength of the noise at frequency fmin. Application to air intake and outlet conduits of aircraft systems.

## Claims

### Claim 1

A device for reducing the noise emitted by a conduit belonging to an aircraft system, comprising:
an acoustic grid positioned in a segment T1 of the conduit, said grid having a length L1, along the axis of said segment, and including multiple meshes, each of which fits into a square with side m, the following relationships being satisfied:
L1>1.8λfmin
m<λfmax/2,
where fmax is the maximum frequency of the noise to be attenuated,
fmin is the minimum frequency of the nice to be attenuated,
λfmax is the wavelength of the noise at frequency fmax, and
λfmin is the wavelength of the noise at frequency fmin.

### Claim 2 (depends on 1)

The device according to claim 1, wherein the grid includes a central opening whereof the transverse dimension is, in any transverse direction of the conduit, smaller than 0.75 D, where D designates the opening dimension of the conduit in the same transverse direction.

### Claim 3 (depends on 1)

The device according to claim 1, wherein, seen from the end, the grid has a square mesh.

### Claim 4 (depends on 1)

The device according to claim 1, wherein, seen from the end, the grid has meshes made up of radial partitions relative to the axis of said segment T1 and walls substantially parallel to the inner wall of said segment T1.

### Claim 5 (depends on 1)

The device according to claim 1, further comprising, upstream from the grid relative to the propagation of the noise, an acoustic damping layer arranged around at least part of the periphery of the upstream segment of the conduit.

### Claim 6 (depends on 5)

The device according to claim 5, wherein the damping layer is adjacent to the upstream end of the grid.

### Claim 7 (depends on 5)

The device according to claim 5, wherein the upstream segment is made up of a metal or composite web.

### Claim 8 (depends on 5)

The device according to claim 5, wherein the acoustic damping layer has a length L2 and a thickness e verifying the following relationships:
L2>λfmax,
and
e>λfmax/4.

### Claim 9 (depends on 1)

An aircraft conduit belonging in particular to a system of the aircraft, equipped with a device according to claim 1.

### Claim 10 (depends on 9)

The aircraft conduit according to claim 9, emerging on an opening of the fuselage of the aircraft, the grid being configured, at its output, in a grid with an esthetic and/or aerodynamic function substantially positioned in that opening of the fuselage.