WO2008015215A2

WO2008015215A2 - Arrangement with an active noise reduction system

Info

Publication number: WO2008015215A2
Application number: PCT/EP2007/057904
Authority: WO
Inventors: Harry Bachmann; Sigmund Eggenberger
Original assignee: Anocsys Ag
Priority date: 2006-07-31
Filing date: 2007-07-31
Publication date: 2008-02-07
Also published as: WO2008015215A3

Abstract

An arrangement with an active noise reduction system for reducing or eliminating disruptive noise in a room (1) having at least one window (9) is disclosed. The arrangement comprises: - a processing unit (20), - at least one sensor unit (21, 22) in the room (1), and - at least one actuator unit (24) in the room (1), the at least one sensor unit (21, 22) and the at least one actuator unit (24) being operatively connected to the processing unit (20). The invention is distinguished in that at least one exterior sensor unit (16) and at least one exterior actuator unit (17) are arranged outside the room (1), both the at least one exterior sensor unit (16) and the at least one exterior actuator unit (17) being operatively connected to the processing unit (20).

Description

Arrangement with an active noise reduction system

The present invention relates to an arrangement with an active noise reduction system for reduction or

Elimination of disturbing noises according to the preamble of claim 1.

Noise sources are increasingly perceived as environmental pollution and are regarded as a reduction of

Life quality. In particular, noise is also disturbing in living spaces and business locations. However, as noise sources are often unavoidable, noise reduction methods based on the principle of wave cancellation have already been proposed. The principle of Active Noise Canceling (ANC) is based on the cancellation of sound waves due to interference. These interferences are generated by one or more electro-acoustic transducers, such as loudspeakers. The signal radiated by the electro-acoustic transducers is calculated by means of a suitable algorithm and continuously corrected. The basis for the calculation of the signal to be radiated by the electroacoustic transducers is the information supplied by one or more sensors. These are on the one hand information about the nature of the signal to be minimized. For this purpose, for example, a microphone can be used which detects the noise to be minimized. On the other hand, information about the remaining residual signal is needed. Again, microphones can be used. The basic principle used with active noise reduction was Paul Lueg in a patent document from the year 1935 and the disclosure number AT-141 998 B described. By this document is disclosed how noise in a tube can be extinguished by generating a signal with opposite phase. An active noise reduction system requires information from at least one sensor (such as a microphone) that determines the residual error. Depending on the application and the algorithm used, additional sensors are provided that provide information about the nature of the signal to be minimized. Further, an active noise reduction system requires one or more actuators (for example in the form of loudspeakers) for outputting the

Correction signal. The information from the sensors must be converted from an analog-to-digital converter into a digital format. After being processed by the algorithm, the signal is retransmitted by a digital to analogue converter and transmitted to the actuators. The effectiveness and efficiency of an ANC system in a room now depends, among other factors such as computing power and processing speed, also substantially on the acoustic properties of the actuators (such as speakers) and sensors

(eg microphones) and their placement. With soundproof windows, very good damping is achieved, especially in the upper frequency range. When the windows are open or partially open, which is often from a technical point of view or as a result of preferences Person in the room is seasonally expedient, there is no or at least only a minimal noise reduction by such passive measures.

The distance between a sensor and an actuator is an important factor in an ANC application according to wavefield synthesis, and it is advantageous to place combinations, each consisting of one sensor and one actuator, close to each other, the effectiveness of this measure with respect to the achieved noise reduction, especially at low frequencies (preferably in the range below 300 Hz) shows. A known application of this principle is, for example, an ANC headphone, based on a feedback arrangement that corresponds to a classic control loop, wherein the microphone signals are routed via a suitable controller to a loudspeaker. As a result, background noise in the music listener can be reduced by several dB.

Other known embodiments of an ANC system are based on a feedforward arrangement in which the signals from additional reference sensors (for example microphones) are fed to the loudspeakers via an adaptive algorithm.

Furthermore, it is expedient to minimize a disturbing noise as possible at the source, so for example before a disturbing noise has spread in a room in accordance with the laws of physics. For the correct and reliable functioning of an ANC system is thus the choice of actuators and sensors as well as the spatial and spatial placement of these elements crucial.

The object of the present invention is therefore to provide an arrangement of sensor and actuator units, which is suitable for active noise reduction and at the same time does not have the above disadvantages.

This object is achieved by the features stated in the characterizing part of claim 1. Advantageous embodiments are specified in further claims.

The invention relates to an arrangement with an active noise reduction system for the reduction or elimination of disturbing noises in a room with at least one window. The inventive arrangement comprises:

a processing unit,

at least one sensor unit in the room, at least one actuator unit in the room, wherein the at least one sensor unit and the at least one actuator unit are operatively connected to the processing unit. The invention is characterized in that at least one outer sensor unit and at least one Außenaktuatoreinheit are arranged outside the room, wherein both the at least one outer sensor unit and the at least one Außenaktuatoreinheit are operatively connected to the processing unit. The arrangement according to the invention has the particular advantage that the sound entering the room is already reduced in the area in front of the window. Thus, in one embodiment variant, the outer sensor and outer actuator units are positioned in the region in front of a window, for example in the region of a roller shutter or a sun blind.

A variant of the inventive arrangement is that both the at least one

Outside sensor unit and the at least one Außenaktuatoreinheit are arranged in the region of the at least one window.

A further embodiment variant of the arrangement according to the invention is that the number of external sensor units is equal to the number of external actuator units.

A still further embodiment variant of the arrangement according to the invention consists in that in each case an external sensor unit and an external actuator unit form a combined actuator / sensor unit.

Another variant of the inventive arrangement is that an even number of combined actuator / sensor units is present.

Another variant of the inventive arrangement is that the combined Actuator / sensor units are arranged around the window, wherein in each case two combined actuator / sensor units are arranged opposite to each other.

A further embodiment variant of the arrangement according to the invention consists in that at least two combined actuator / sensor units are arranged horizontally opposite and / or at least two combined actuator / sensor units vertically opposite one another.

A further embodiment variant of the arrangement according to the invention consists in that the actuator units are loudspeakers.

Yet another embodiment of the inventive arrangement is that the sensor units are microphones.

A further embodiment variant of the arrangement according to the invention consists in that the active noise reduction can be carried out on the "feedforward" principle.

A further embodiment variant of the arrangement according to the invention consists in the fact that an algorithm of the type "feedforward" or of the type "feedback" can be used in the processing unit.

A further embodiment variant of the arrangement according to the invention is that to achieve a further Noise reduction passive measures, in particular a use of sound-insulating windows, can be used.

Hereinafter, the present invention is further explained by means of exemplary embodiments with reference to drawings. Show it:

Fig. 1 shows a room with an active

Noise reduction system in a schematic representation,

Fig. 2 is a highly simplified block diagram of a

Noise reduction system using a known "feedback" method,

FIG. 3 is a simplified equivalent circuit diagram of an active noise reduction system using a known "feedforward" method. FIG.

4 shows a cross section through the wall of a room equipped with a window with an inventive arrangement of the actuator or sensor units, again in a schematic representation,

Fig. 5 shows a further cross section through the with a

Window equipped wall of a room with an inventive arrangement of the actuator or sensor units, again in a schematic representation, Fig. 6 is an elevation of a wall of a room equipped with a window with a erfmdungsgemassen arrangement of actuator or sensor units, again in a schematic

Presentation,

7 is another elevation of a wall of a room equipped with a window with a erfmdungsgemassen arrangement of actuator or

Sensor units, again in a schematic representation, and

8 is a highly simplified block diagram of an active noise reduction system using a known algorithm.

1 shows a room 1 with a window 9 in plan view with an active noise reduction system, which consists of a processing unit 20, a sensor unit 21, an actuator unit 24 and an outdoor sensor unit 22. The processing unit 20 is operatively connected via connections 19 to the sensor unit 21, the actuator unit 24 and the external sensor unit 22. While the sensor unit 21 is placed inside the room 1 to be quieted for detecting residual noise, the outside sensor unit 22 for detecting noises is arranged in an outside area 2 outside the room 1. With the actuator 24, a correction signal is output to the room 1, with which the in Room 1 occurring unwanted noise eliminated or at least attenuated. The sensor units 21 and the outdoor sensor unit 22 are preferably designed as microphones and the actuator units 24 preferably as loudspeakers.

Fig. 2 shows a block diagram of a

Noise reduction system in the arrangement of a known feedback method. The output signal of a microphone 21 is applied to a processing unit 20, which generates a correction signal and transmits it to a loudspeaker unit 24.

Fig. 3 shows an equivalent circuit diagram of an embodiment variant in a schematic representation. It is a so-called adaptive

Noise reduction system (ANC), with the help of which a noise in a room 1 (Fig. 1 or 2) using the principle of signal cancellation is eliminated or at least reduced. The space 1 to be monitored has a transfer function H, which is supplied with an input signal x. This is an input signal x recorded with the aid of a microphone unit (not shown in FIG. 3), which is further supplied to a filter unit 3 and an adaptive calculation unit 4. An actual output signal d, which is formed by the transfer function H and the input signal x, is compensated in space 1 by an estimated output signal y by applying this to a loudspeaker (not shown in FIG Room 1 is supplied. So that the compensation of the actual output signal d can take place completely, the transfer function H of the room 1 is estimated in the filter unit 3 with the aid of a in the adaptive calculation unit 4. The result of the estimation is an estimated transfer function H, from which the estimated output signal y is generated together with the input signal x. The superposition of the two output signals y and y is shown in the equivalent circuit diagram of FIG. 3 with an addition unit 5, wherein the sign of the estimated output signal y is reversed before addition, so that as a result of the addition of the difference (hereinafter referred to as error signal e) both output signal y and y is present. This error signal e is fed together with the input signal x to the adaptive calculation unit 4, in which the coefficients of the estimated transfer function H are set in such a way that the error signal is as small as possible using an adaptive algorithm, for example an Fx algorithm. A suitable one

Algorithm with a feedback element will be explained with reference to FIG.

The transfer function H describes the acoustic behavior of the room 1. In addition to the acoustic behavior in the transfer function H also

Transmission characteristics of the components used, such as the microphone unit for receiving the input signal x and the speaker unit for outputting the inverted estimated output signal y included. FIG. 4 shows a cross section through a wall of a room 1 equipped with a window 9 with an arrangement according to the invention of the actuator or sensor units. Sound waves 14 of the sound source 15 located in the outer area 2 propagate wave-shaped, are detected by an outdoor sensor unit 22 (for example a microphone) and impinge on the masonry 10, 10 ^x and on the outer window pane 11. According to the invention, further external sensor units 16 (for example microphones) and others

Aussenaktuatoreinheiten 17 (for example, speaker) placed in the area of the window frame 13, 13 ^Λ or surrounding walls 10 on the building exterior, and serve to sound reduction of light emitted from the source 15 the sound field in the region between the window 11 and the source 15. For example, in a window with Double glazing is the outer window 11 separated by the gap 12 of the inner window 11 11 ^, and the two windows 11 and 11 ^x are fixed in the window frame 13, which in turn is anchored in the masonry 10, 10 ^λ . The residual sound passing through the open or closed window 9 into the room 1 is detected on the one hand by the sensor unit 21 in the room 1 (for example a microphone), and the correction signal (estimated output signal y) is transmitted by the actuator unit 24 (for example a loudspeaker), thus a further reduction of noise in room 1 takes place. The Sensor units 16, 21, 22 and the actuator units 17, 24 are operatively connected to the processing unit 20.

5 again shows a cross section through a wall 23 of a room 1 provided with a window 9 with an arrangement of the actuator or sensor units according to the invention, wherein, in contrast to FIG. 4, the outer sensor unit 16 and the outer actuator unit 17 advantageously turn into one an actuator and a sensor unit existing, combined unit 18 are summarized. In addition, the window 9 is shown in the half-open state.

Fig. 6 shows the wall 23 of a room 1 in elevation, with a window 9 is located between the ceiling 22 and the bottom 21. Outside the window, the placement of the combined actuator / sensor units 18 takes place in a horizontal arrangement. In addition, in the vertical direction, the combined actuator / sensor units 19 are arranged so that by selecting the distances xl, yl advantageously optimal sound reduction in the horizontal and vertical directions is achieved. It is expressly pointed out that instead of the combined actuator / sensor units 18, 19, it is also possible to use individual actuator units 17 and individual sensor units 16, without the principle according to the invention being abandoned.

The distances xl, yl of the combined actuator / sensor units 18, 19 is possible on the Wavelength λ of the interference signal to be eliminated tuned. If the distances x1, y1 are the same size as half the wavelength (ie λ / 2), a maximum extinction of the interference signal is obtained. In the event of a deviation from this optimum setting for a noise signal with a certain frequency or if a noise with a certain spectral distribution is to be eliminated or at least reduced, the noise reduction takes place in a correspondingly reduced manner.

For example, road or aircraft noise has an approximate center frequency of 500 Hz. This results in an average propagation velocity of a sound wave in air of 300 m / s a value for λ / 2 of about 30 cm. Accordingly, the combined

Actuator / sensor units 18 and 19 to be arranged at a distance of 30 cm.

In a further embodiment of the present invention, provision is made for a multiplicity of combined actuator / sensor units to be arranged along the window frames. This creates the possibility that the largest possible spectrum of noises can be eliminated or reduced. It is conceivable, depending on the frequency of the noise, that certain combined actuator / sensor units, which are in a favorable distance from each other according to the above rules, are used for the elimination or the reduction of the noise. 7 again shows the wall 23 of a room 1 with a window 9. In contrast to FIG. 6, in this example the window 9 has smaller dimensions, which reduces the number of combined actuator / sensor units. The arrangement is again in a horizontal and vertical manner, wherein by selecting the distances x2, y2 advantageously optimal sound reduction in the horizontal and vertical directions is achieved. The same rules for determining the distances x2 and y2 are also used in this embodiment, as was already the case with the embodiment according to FIG. 6 for the distances x1 and y2.

8 shows a still further block diagram of an embodiment variant in a schematic representation. Since the actuator unit is located locally close to the sensor unit (eg, a reference microphone), it is recommended to use an algorithm that has a feedback. In addition to FIG. 3, the output signal y estimated by the filter 3 is applied in addition to the feedback unit 8 and is paid together in the addition unit 5 with the actual output signal d. The output signal y ^x the

Feedback unit 8 is paid after previous inversion in a further addition unit 29 with the input signal x together, wherein the sum signal x ^{λ of} both the adaptive calculation unit 4 and the filter 3 is applied.

Claims

claims

An arrangement having an active noise reduction system for reducing or eliminating disturbing noises in a room (1) having at least one window (9), the arrangement comprising:

a processing unit (20),

- at least one sensor unit (21, 22) in the space (1), - at least one actuator unit (24) in the space (1), wherein the at least one sensor unit (21, 22) and the at least one actuator unit (24) with the processing unit ( 20) are operatively connected, characterized in that at least one outer sensor unit (16) and at least one

External actuator unit (17) outside the space (1) are arranged, wherein both the at least one outer sensor unit (16) and the at least one Außenaktuatoreinheit (17) with the processing unit (20) are operatively connected.

2. Arrangement according to claim 1, characterized in that both the at least one outer sensor unit (16) and the at least one Außenaktuatoreinheit (17) in the region of the at least one window (9) are arranged.

3. Arrangement according to claim 1 or 2, characterized in that the number of outer sensor units (16) is equal to the number of Außenaktuatoreinheiten (17).

4. Arrangement according to claim 3, characterized in that in each case an external sensor unit (16) and an external actuator unit (17) form a combined actuator / sensor unit (18, 19).

5. Arrangement according to claim 4, characterized in that an even number of combined actuator / sensor units (18, 19) is present.

6. Arrangement according to claim 5, characterized in that the combined actuator / sensor units (18, 19) are arranged around the window (9), wherein in each case two combined actuator / sensor units (18, 19) are arranged opposite each other.

7. Arrangement according to claim 6, characterized in that at least two combined actuator / sensor units (18) horizontally opposite and / or at least two combined actuator / sensor units (19) are arranged vertically opposite.

8. Arrangement according to one of claims 1 to 7, characterized in that the actuator units (17, 24) are loudspeakers.

9. Arrangement according to one of claims 1 to 8, characterized in that the sensor units (16, 21, 22) are microphones.

10. Arrangement according to one of claims 1 to 9, characterized in that the active noise reduction on the "Feedforward" Pπnzip vornehmbar.

11. Arrangement according to one of claims 1 to 10, characterized in that in the processing unit (20) an algorithm of the type "feedforward" or of the type "feedback" is applicable.

12. Arrangement according to one of claims 1 to 11, characterized in that to achieve a further noise reduction passive measures, in particular a use of sound-insulating windows, can be used.