DE102009045463A1 - Sound reducing device for use in e.g. airliner, in airport, has explosion acoustic source producing counter noise, and control device controlling source based on sound characteristics such that sound and counter noise are mutually reduced - Google Patents

Abstract

The device (9) has a measuring device i.e. microphone (10), measuring characteristics of sound (8), and an explosion acoustic source (14) producing counter noise (16). A control device (12) is signal-technically connected with the measuring device and the acoustic source. The control device controls the acoustic source depending on characteristics of the sound such that the sound and the counter noise are mutually reduced. The control device provides a distance (X) between the measuring device and the acoustical source during controlling of the source. Independent claims are also included for the following: (1) a vehicle having a device for reducing sound (2) a method for reducing sound.

Description

The present invention relates to a device for at least reducing sound, to a vehicle with this device, and to a method for at least reducing sound.

Although applicable in any field of technology, the present invention and its underlying problem with respect to a commercial aircraft are explained in more detail.

Commercial aircraft have a variety of sound sources that generate sound that is disruptive to the environment. This sound is also referred to as noise (English: noise). Examples of such sound sources are the engines, flaps on the wings or the chassis. In or behind the engine, for example, the sound is generated due to the high velocity combustion gases and the interaction of the rotors with the passing air. At the flaps or on the chassis, the sound is generated during the flight due to the high-speed impact on the flaps or the chassis ambient air.

In the prior art, a variety of methods have become known in order to reduce the sound, in particular often to meet legal requirements regarding Schallobergrenzen.

In principle, two types of sound reduction can be distinguished from one another in the prior art, namely passive and active noise reduction.

In passive noise reduction, for example, silencers or other mechanical means are provided in the region of the inlet and outlet of an engine. These form mechanical dampers and thus withdraw the sound of the sound, so reduce this.

For active noise reduction it has become known to provide counter-noise sources, which generate a counter-sound, in the area of the sound sources or also at the location where the sound is to be reduced. This counter sound is so out of phase with respect to the sound and formed with an identical frequency and amplitude, so that at least reduce each other and extinguish sound and counter-sound. The counter-sound sources for generating the counter-noise are typically formed in the prior art as speakers with piezoelectric actuators, such as in the US 5,386,689 described.

In the active sound reduction described above, it has proved to be disadvantageous that the speakers are comparatively large and heavy and can generate the counter-noise with only a small power.

The object of the present invention is at least to reduce the disadvantages described above.

According to the invention, this object is achieved by a device having the features of patent claim 1, by a vehicle having the features of patent claim 5 and / or by a method having the features of patent claim 9.

Accordingly, an apparatus for at least reducing sound, in particular in the aerospace sector, comprises: a measuring device for measuring characteristics of the sound; an explosion sound source, which is designed to generate a counter-sound; and a control device, which is signal-technically connected to the measuring device and the explosion sound source and controls the explosion sound source as a function of the characteristics of the sound such that the sound and the counter-sound at least reduce each other; provided.

Furthermore, a vehicle, in particular an aircraft or spacecraft, is provided with the device according to the invention, wherein the device is designed to at least reduce a sound in the region of the vehicle.

Furthermore, a method is provided for at least reducing sound, in particular for performing with the device according to the invention or with the vehicle according to the invention, wherein a counter sound is generated by means of an explosion sound source such that the sound and the counter sound at least reduce each other.

The idea underlying the present invention is that explosion sound sources (English: pulse combustor) can produce a counter-sound with a very high pressure amplitude with only small size and low weight. This makes them particularly attractive for applications in the aerospace sector, where it is necessary to reduce sound with a very high pressure amplitude. For example, by means of the invention, night flight restrictions for aircraft serving to protect the residents of airports could be considered superfluous.

In this case, an "explosion sound source" is to be understood as meaning any device that is designed to generate explosions in a controlled manner, so that a counter sound is generated with a specific, in particular adjustable frequency, phase and / or pressure amplitude. The explosion can take place inside or outside the facility.

The explosion sound source may be configured to operate solely in a detonation mode or only in a deflagration mode. Alternatively, the explosion sound source may be configured to operate in the detonation mode or in the deflagration mode.

In the detonation mode, the ratio of combustion constituents is adjusted so that they burn very rapidly to produce very high pressures. The generated sound pressure is correspondingly large. In this mode, each explosion is triggered by providing an appropriate amount of combustion constituents and igniting them at an appropriate time by means of an igniter.

In the deflagration mode, the ratio of the combustion constituents is adjusted so that they burn more slowly to produce lower pressures. The generated sound pressure is correspondingly lower. In the deflagration mode, the combustion constituents ignite themselves. For example, this can take place as follows: The combustion constituents are introduced into a pipe section which adjoins an initially closed end of the pipe. After that, the combustion constituents are ignited once by means of an ignition device. The combustion of the combustion constituents causes the air cylinder, which is arranged in a pipe section, which is adjacent to an open end of the pipe, is ejected from this. The pressure in the tube subsequently decreases slightly below the ambient pressure due to overexpansion of the combustion products, thereby drawing in fresh combustion constituents through a valve in the region of the initially closed end of the tube. The fresh combustion constituents ignite spontaneously when they come into contact with residues of the old combustion products, causing a new explosion.

The device according to the invention and / or the method according to the invention can not only be used in a vehicle. In addition to aircraft or spacecraft, especially helicopters, come as vehicles and motor vehicles, railways and military vehicles, especially tanks, into consideration. In particular, in the military sector, the device according to the invention could be used to temporarily allow a crawl. Furthermore, the device according to the invention and / or the method according to the invention can be used, for example, at airports, industrial plants, highways etc.

The measuring device is preferably designed as a microphone.

In the subclaims there are advantageous embodiments and improvements of the invention.

According to a preferred development of the device according to the invention, the explosion sound source has at least one connection for supplying one or more combustion constituents and at least one ignition device for igniting the combustion constituents. The controller may control the igniter to ignite the combustion constituents at a suitable frequency to generate the counter sound at the desired frequency. The necessary sound pressure of the counter-sound can be adjusted by means of the supplied quantity of the combustion constituents and / or by the ratio of the combustion constituents to one another. Furthermore, it is possible to otherwise control the frequency of the counter-noise. This may be done, for example, mechanically by, in particular, forming a pipe in which the combustion constituents are exploded with an appropriate length and operating the explosion in the deflagration mode described above. The explosion sound source can be operated, for example, according to the principles of Schmidt, Helmholtz or Rijke. The port may be in the form of a valve, the valve being connected to the controller and being opened and closed by it at a suitable frequency to supply the combustion constituents.

According to a further preferred development of the device according to the invention, the control device is set up to take into account the distance between the measuring device and the explosion sound source in the control of the explosion sound source. Due to the distance between the measuring device and the explosion sound source, the sound in the region of the measuring device can have different characteristics, in particular a different phase and / or a different frequency, than in the region of the explosion sound source. The control device can be provided, for example, with a memory on which a table or / or an algorithm is stored, by means of which it is possible to predict its characteristics in the region of the explosion sound source on the basis of the characteristics of the sound at the measuring device. According to this prediction then the counter sound in the area of Explosion sound source generated so that sound and counter-noise at least reduce each other.

According to a further preferred development of the device according to the invention, the control device is set up to compensate for delays due to its own computing time. For example, the measuring device measures the characteristics of the sound at a time T1. The explosion sound source generates - in particular due to the computing time of the control device - at a slightly later time T2 the corresponding counter sound. In the period T2 minus T1, however, as a rule the sound has already changed, in particular with regard to its phase. The control device can accordingly have a memory on which a table and / or an algorithm is stored, by means of which the change can be predicted, and the control device is controlled in such a way that sound and counter sound are at least mutually reduced.

The control device can also be set up to compensate for other delays. For example, when controlling the counter-sound source, the control device can take into account the period of time which lies between ignition of the ignition device and the emergence of the counter-sound wave, that is to say the period required by the combustion constituents for their combustion.

According to a further preferred development of the vehicle according to the invention, this has a drive device for driving the vehicle, wherein the drive device and the explosion sound source can be operated with the same chemical fuel as the combustion constituent. This has the advantage that no separate fuel for the explosion sound source must be carried, which facilitates the provision of fuel and also opens the possibility common components such. B. to use a common tank. For aircraft applications, kerosene is particularly suitable as a combustion constituent.

According to a further preferred development of the vehicle according to the invention, a drive device and a feed device are provided, wherein the feed device is adapted to supply a bleed air of the drive device of the explosion sound source to oxygen in the bleed air as the first combustion constituent with a chemical fuel as the second combustion constituent in the explosion sound source To bring explosion. At high altitudes, as is the case during flight operation of an aircraft, the air density of the ambient air and thus the proportion of oxygen contained per air volume is low. The bleed air from the drive device, ie from a compressor stage of the engine, however, is compressed, so that the oxygen content in this per air volume is high compared to the ambient air. The exploded sound source with bleed air is therefore very powerful. In particular, a combustion chamber of the explosion sound source can be made small due to the high oxygen density of the bleed air.

Kerosene, gasoline, diesel or hydrogen come into question in particular as the second combustion constituent. It is also conceivable to use a solid, for example carbon in powder form, as the second combustion constituent. Alternatively, the explosion sound source can also be operated with a single combustion constituent, which burns by decomposing into its constituents, as is the case, for example, with nitroglycerin.

With drive means in the present case any type of engine or internal combustion engine is meant. These can be designed with or without a propeller, turbine engine or piston engine. Examples of such drive devices are a turbofan engine, a turbojet engine or a turboprop engine.

According to a further preferred development of the vehicle according to the invention, a drive device for driving the vehicle is provided, wherein the control device is set up to take into account data from a management device of the drive device in the control of the explosion sound source. For example, the management device can report to the control device that the rotational speed of the drive device is increased. On a memory of the control device, a table and / or an algorithm can be deposited, by means of which the characteristics of the sound can be predicted, which will arise at the higher speed. The control device can then control the explosion sound source and thus the counter sound generated by it, such that the counter sound changes simultaneously with the sound, the latter due to the increase in the rotational speed, and these continually reduce each other at least. Without the development described above, it may be the case that the control device first has to react to the changed rotational speed and the associated altered sound, whereby hardly any avoidable time delay arises in which the sound is insufficiently reduced by the counter-sound.

According to a further preferred embodiment of the method according to the invention, characteristics of the sound are measured and the explosion sound source is determined as a function of the characteristics of the sound for generating the counter sound is controlled. Thus, the counter sound can be generated specifically.

The developments and advantages described herein for the device according to the invention are correspondingly applicable to the method according to the invention and to the vehicle according to the invention and vice versa.

The invention is explained in more detail below on the basis of exemplary embodiments with reference to the accompanying figures of the drawing.

From the figures show:

1 in a schematic sectional view of a section of an aircraft according to an embodiment of the present invention;

2 schematically the supply of combustion constituents for the explosion sound sources 1 ; and

3 schematically an alternative embodiment of the explosion sound source opposite 2 ,

In the figures, the same reference numerals designate the same or functionally identical components, unless indicated otherwise. Furthermore, in the figures, signal paths are indicated by means of lines which have an arrowhead.

1 shows a section of an aircraft in a sectional view 30 (please refer 2 ) according to an embodiment of the present invention.

This in 1 partially shown engine 2 has rotors 4 on, moving at high speed around an axis 6 rotate. At the engine 2 For example, it is a jet engine.

Due to the high rotational speed of the rotors 4 they vibrate and produce sound 8th The environment often perceives as disturbing noise and therefore it has to be reduced. For this purpose is a device 9 with microphones 10 provided which characteristics, ie phase, frequency and amplitude, of the sound 8th measure up. Using cable or wireless will be in the microphone 10 generated measuring signals to a control device 12 the device 9 transfer. The control device controls in dependence on the measuring signals 12 Explosion sound sources 14 the device 9 for generating a counter sound 16 , The counter sound 16 has such characteristics, ie phase, frequency and amplitude, so that the sound 8th and the counter-sound 16 essentially obliterate.

The control device 12 can also be equipped with a management facility 18 of the plane 30 be connected by signal technology. The management facility 18 controls the engine, so in particular its speed, fuel supply, etc. Further, the management device receives 18 Signals from the pilot, for example to increase the thrust of the engine 2 , Because of these signals the pilot becomes the management device 18 the engine 2 control accordingly, so for example increase the fuel supply. These control signals of the management device 18 can contact the controller 12 be transmitted. On the basis of the control signals which, for example, at a time T1 to the engine 2 and parallel to the controller 12 are transmitted, predicts the controller 12 the sound present at a later time T2. The control device 12 then controls the explosion sound sources 14 in such a way that at time T2 a counter sound is produced 16 generate, so that the counter sound 16 and the sound 8th essentially extinguish at time T2. The prognosis can be made, for example, by means of a table or an algorithm, which or which in the control device 12 is deposited. In the table, for example, at time T2 expected sound pressure for a the engine 2 be deposited at the time T1 amount of fuel. Accordingly, then the sound pressure of the counter sound 16 from the controller 12 be set. Of course, from the controller 12 a large number of other control parameters of the management device 18 , z. B. a speed of the engine, are taken into account, which will not be explained in detail below.

As 1 refer to the microphone 10 a distance X to the explosion sound source. The one from the microphone 10 measured characteristics of sound 10 , in particular its phase, may therefore be other than those which are in the vicinity of the explosion sound source 14 available. Since the distance X and other parameters are known, the control device 12 be set up based on the measurement signals of the microphone 10 actually in the area of the explosion sound source 14 present sound 8th to calculate. This can be done for example by means of appropriate tables or algorithms. In the table, for example, a certain, measured sound, described by the characteristics phase, frequency and amplitude, a certain expected sound 8th with its characteristics, ie phase, frequency and amplitude, in the area of the explosion sound source 14 be assigned. The explosion sound source 14 is then according to the certain, expected sound 8th controlled. For example, it is possible that in the table - or in the algorithm - a current air pressure is taken into account, as this may be due to the expected sound 8th effect.

In the foregoing it has already been described that the explosion sound source 14 depending on measuring signals of the microphone 10 is controlled. Even when using a real-time computer, the explosion sound source can 14 only - if only slightly - delayed in the measuring signals of the microphone 10 react. It follows that the characteristics of the sound 8th , in particular its phase, change within the time offset. The control device 12 may be configured to compensate for this using, for example, a table and / or an algorithm.

The explosion sound source 14 For example, as in 2 shown schematically, be formed. According to this embodiment, the explosion sound source has a mixing chamber 20 on. The mixing chamber 20 is at one end with connections 22 and 24 formed in the form of valves. The valve 22 is by means of a line 26 with a fuel tank 28 of the plane 30 connected. The fuel tank 28 Contains kerosene, which is primarily for combustion in the engines 2 of the plane 30 is intended to generate thrust.

The valve 24 is by means of a line 32 with a bleed air line 34 of the engine 2 connected. The bleed air line 34 The primary task is to compressed air from a compressor, not shown, of the engine 2 to tap and the cabin, not shown, of the aircraft 30 to be printed on and to supply fresh air to the passengers and the crew.

The valves 22 and 24 be steplessly, by the control device, for example, between an open position in which they kerosene or bleed air into the mixing chamber 20 let in, and a closed position in which no bleed air or kerosene in the mixing chamber 20 passes, controlled.

In the mixing chamber 20 The kerosene and the bleed air mix. The bleed air is under pressure and expands through a nozzle together with the kerosene distributed in it 36 at the valves 22 and 24 in the opposite end of the mixing chamber 20 , The mixture 38 then strokes over a spark plug 40 ,

The spark plug 40 is also from the controller 12 driven. The spark plug 40 generated in one of the control device 12 given frequency a spark. The spark ignites the mixture 38 which then explodes. Depending on the mixing ratio of kerosene and bleed air, it may be a detonation or a deflagration. This creates the counter sound 16 ,

The amplitude of the counter sound 16 can be controlled for example by the absolute amount and / or by the ratio of kerosene to bleed air. The frequency of the counter sound 16 can be, for example, by means of the frequency of the spark plug 40 control with which this is ignited. The valves 22 and 24 can be opened before each ignition and closed again to get a sufficient amount of mixture 38 provide. Likewise, the valves can 22 and 24 but also be constantly open, with the frequency of the counter sound 16 exclusively by means of the spark plug 40 is controlled.

In 2 are other areas of the aircraft 30 characterized in which sound 8th , which is noticeable as disturbing noise arises. These areas are in particular the chassis, the fuselage skin, the vertical tail, the engine gland outer sides and the flaps. In all these areas can devices 9 to reduce the sound 8th be provided.

Relating to 3 subsequently becomes an explosion sound source 14 according to a further embodiment of the present invention, wherein only the differences with respect to the explosion sound source 14 according to 2 will be received.

The explosion sound source 14 has a pipe 42 on, at the closed end of the valves 22 and 24 are arranged and the other end is formed open. The pipe 42 has a mixing and combustion chamber 44 in its interior. The spark plug 40 extends into the mixing and combustion chamber 44 , The valves 22 and 24 let kerosene or bleed air into the mixing and combustion chamber 44 a, whereby these to the mixture 38 mix which of the spark plug 40 is ignited. The mixture 38 then explodes and generates the counter-sound 16 ,

Also the explosion sound source 14 according to this embodiment can be operated in the detonation or deflagration mode. The spark plug 40 can be operated to trigger any explosion (detonation mode). Alternatively, the explosion sound source 14 be operated such that always a residual gas cylinder 46 from the previous explosion in the pipe 42 which is the mixture 38 ignited for the subsequent explosion (deflagration mode). In this case, so only a single ignition by means of the spark plug 40 necessary. The frequency of the explosions then arises among other things from the length of the tube 42 and the amount of the mixture 38 , Here also the principles of Schmidt, Helmholtz or Rijke can be applied.

It is also possible the explosion sound source 14 operate such that by means of a in the pipe 42 due to the previous explosion existing negative pressure kerosene and bleed air in the mixing and combustion chamber 44 is sucked in automatically, without having to be injected separately.

The device 9 can be operated with normal ambient air instead of bleed air. Alternatively, it is also conceivable to carry oxygen in bottle form, for example.

The device 9 can be operated to reduce or cancel the sound throughout the flight time to relieve the passengers, or even only during takeoff and landing when the aircraft is near the ground, to relieve the environment near the airport.

LIST OF REFERENCE NUMBERS

2

engine

4

rotor

6

axis

8th

sound

9

contraption

10

microphone

12

control device

14

Explosion sound source

16

countersound

18

management device

20

mixing chamber

22

connection

24

connection

26

management

28

fuel tank

30

plane

32

management

34

Bleed air line

36

jet

38

mixture

40

spark plug

42

pipe

44

Mixing and combustion chamber

46

Residual gas cylinder

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 5386689 [0007]

Claims (10)

Contraption ( 9 ) for at least reducing sound ( 8th ), in particular in the aerospace sector, comprising: a measuring device ( 10 ) for measuring characteristics of the sound ( 8th ); an explosion sound source ( 14 ), which is designed to counter-sound ( 16 ) to create; and a control device ( 12 ), which with the measuring device ( 10 ) and the explosion sound source ( 14 ) is technically connected and the explosion sound source ( 14 ) depending on the characteristics of the sound ( 8th ) controls such that the sound ( 8th ) and the counter sound ( 16 ) at least reduce each other. Apparatus according to claim 1, characterized in that the explosion sound source ( 14 ) at least one connection ( 22 . 24 ) for supplying combustion constituents and at least one ignition device ( 40 ) for igniting the combustion constituents. Device according to claim 1 or 2, characterized in that the control device ( 12 ) is arranged to maintain a distance (X) between the measuring device ( 10 ) and the explosion sound source ( 14 ) in the control of the explosion sound source ( 14 ). Device according to at least one of the preceding claims, characterized in that the control device ( 12 ) is set up to compensate for delays due to its own computing time. Vehicle ( 30 ), in particular an aircraft or spacecraft, with a device ( 9 ) according to at least one of the preceding claims, wherein the device ( 9 ) is adapted to produce a sound ( 8th ) in the area of the vehicle ( 30 ) at least reduce. Vehicle according to claim 5, characterized in that a drive device ( 2 ) for driving the vehicle ( 30 ) is provided, wherein the drive device ( 2 ) and the explosion sound source ( 14 ) are operable with the same chemical fuel as the combustion constituent. Vehicle according to claim 5 or 6, characterized in that a drive device ( 2 ) for driving the vehicle ( 30 ) and a feeder ( 24 . 32 . 34 ) are provided, wherein the feed device is adapted to a bleed air of the engine ( 2 ) of the explosion sound source ( 14 ) to supply oxygen in the bleed air as a first combustion constituent with a chemical fuel as a second combustion constituent in the explosion sound source ( 14 ) to explode. Vehicle according to one of claims 5 to 7, characterized in that a drive device ( 2 ) for driving the vehicle ( 30 ), the control device ( 12 ) is designed to collect data from a management facility ( 18 ) of the drive device ( 12 ) in the control of the explosion sound source ( 14 ). Method for at least reducing sound ( 8th ), in particular for performing with the device ( 9 ) according to one of claims 1 to 4 and / or with the vehicle ( 30 ) according to one of claims 5 to 8, wherein a counter sound ( 16 ) by means of an explosion sound source ( 14 ) is generated such that the sound ( 8th ) and the counter sound ( 16 ) at least reduce each other. Method according to claim 9, characterized in that characteristics of the sound ( 8th ) and the explosion sound source ( 14 ) depending on the characteristics of the sound ( 8th ) for generating the counter sound ( 16 ) is controlled.

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