EP2829079A2

EP2829079A2 - Method for operating a loudspeaker device, loudspeaker device, and device for noise compensation

Info

Publication number: EP2829079A2
Application number: EP13710788.4A
Authority: EP
Inventors: Markus Moser; Rene KORSCH
Original assignee: Audi AG
Current assignee: Audi AG
Priority date: 2012-03-23
Filing date: 2013-03-09
Publication date: 2015-01-28
Anticipated expiration: 2033-03-09
Also published as: DE102012005893A1; EP2829079B1; WO2013139445A2; US20150086027A1; WO2013139445A3; CN104205873B; CN104205873A

Abstract

The invention relates to a method for operating a loudspeaker device (1) with at least one loudspeaker (2), wherein at least one actual membrane state parameter of a membrane (3) of the loudspeaker (2) is detected by a detecting device (15, 16). In the method, an actual membrane state of the membrane, comprising the actual membrane state parameters actual membrane position (x_ist), actual membrane speed (vist) and actual membrane acceleration (aist), is determined from the at least one detected actual membrane state parameter (Xist, aist) and is directly used to determine an actuation signal (U(t)) that is applied to the voice coil (7) of the loudspeaker (2), said voice coil being operatively connected to the membrane (3). The invention further relates to a loudspeaker device (1) and a device for noise compensation.

Description

Method for operating a loudspeaker device,

Loudspeaker device and device for noise compensation

The invention relates to a method for operating a loudspeaker device having at least one loudspeaker, wherein at least one membrane actual state variable of a diaphragm of the loudspeaker is detected by a detection device. The invention further relates to a speaker device and a device for noise compensation.

Methods of the type mentioned are known from the prior art. In particular, the use of an electrodynamic loudspeaker with voice coil and membrane as sound source is well known. Such a speaker is used as part of stereos, for example, in the home, up to high-quality car fidelity systems in the automotive sector. Its essential feature is the conversion of a time-dependent drive signal, which is applied to it or its terminals, in a time-dependent sound level profile, ie in particular a pressure, density and fast course, which is delivered to the environment of the speaker. The drive signal is usually applied to the voice coil of the loudspeaker, which is in operative connection with the membrane and this displaced according to the Ansteuersignais. The conversion of the control signal is generally carried out in such a way that a phase shift between the control signal and the generated sound level is not a constant, but exists as a function of the frequency. This has the consequence that the drive signal or its shape, if it is not a pure sinusoidal, not completely retained when it is converted into the sound history. As a result, it is generally not possible to have the membrane of the loudspeaker follow a predefined position, speed and / or acceleration profile in real time. Rather, only the frequencies in a frequency space, but not the phase or phase shift, correctly reproduced. However, since human hearing can not distinguish phases, such speaker behavior is sufficient for many applications.

In order to achieve a more precise conversion of the drive signal into sound, it is known to detect a diaphragm actual state variable of the diaphragm of the loudspeaker within the scope of the "motional feedback" principle. Nistzustandsgröße used to control the speaker. Even with such a procedure, however, the phase shift between control signal and generated sound changes, usually also here as a function of the frequency.

It is therefore an object of the invention to provide a method which does not have the disadvantage mentioned above, but allows extremely precise control of the speaker, in which in particular the phase shift between the drive signal and the generated sound at different frequencies, preferably over the entire the frequency spectrum that can be converted to the loudspeaker remains constant.

This is achieved according to the invention by the method having the features of claim 1. It is provided that a Membranistzustand the membrane, comprising the Membranistzustandsgrößemembranistposition, Membranistgeschwindigkeit and Membranistbeschleunigung, determined from the at least one detected Membranistzustandsgröße and used directly to determine a Ansteuersignais which is applied to an actively connected to the membrane voice coil of the speaker. In order to achieve the above-mentioned advantages, all three mentioned membrane actual state variables, ie the membrane stop position, the membrane instantaneous velocity and the membrane actual acceleration, are determined from the at least one detected membrane actual state variable. The Membranist position, the Membranistgeschwindigkeit and the Membranistis acceleration are summarized in the Membranistzustand. This is then used as input to determine the drive signal. That is, not just a single membrane population size or individual ones of the membrane population sizes are used to determine the drive signal. Rather, the entire Membranistzustand, which consists of the three mentioned Membranistzustandsgrößen should be used. In this way, a very precise implementation of the drive signal is achieved.

For this purpose, for example, the loudspeaker device is provided with an input signal which, in addition to the membrane state, serves as an input variable for determining the actuation signal. The drive signal is so far as the output size. The relationship between the membrane state or its Membranistzustandsgrößen and the drive signal, for example, is linear. However, a nonlinear relationship may also be provided. In addition, the membrane nistzustand also at least one actual pressure, have, for example, the Schallistdruck behind or in front of the diaphragm of the speaker, in particular at a certain distance to a rest position of the membrane. Both the actual pressure before and the actual pressure behind the membrane are preferably determined. The determination can be carried out by measuring by means of a measuring device or alternatively by calculating in a calculation model. The calculation model can have, for example, at least one of the membrane actual state variables as the input variable and the actual pressure as the output variable.

A further development of the invention provides that the membrane stop position, the membrane actual velocity or the membrane histamine acceleration is used as the at least one detected membrane actual state variable. With the aid of the detection device, at least one of the membrane actual state variables of the membrane actual state is detected. For example, only one of the membrane actual state variables is detected or measured. However, at least two, in particular exactly two, of the membrane actual state variables are preferably detected by means of the detection device. These are in particular the membrane stop position and the membrane acceleration.

A development of the invention provides that for detecting the Membranistposition a distance sensor, in particular an optical distance sensor, preferably a laser distance sensor, is used as a detection device. The distance sensor is arranged stationary so that it can detect its distance from the membrane with sufficient accuracy. From the distance detected by means of the distance sensor, the deflection of the membrane and thus the membrane position can be determined. As a distance sensor is preferably the optical distance sensor used, because with this a contactless detection of the distance is possible. The optical distance sensor has a light source and a light sensor, wherein the light source is directed onto the membrane and the light sensor is arranged such that it detects the light of the light source reflected by the membrane. The optical distance sensor determines the distance, for example by means of a transit time measurement of the light emitted by the light source, by means of a determination of a phase position and / or by means of triangulation. The latter is particularly preferably the case when the optical distance sensor is present as a laser distance sensor (laser triangulation). The laser distance sensor according to its name has a laser emitter serving as a light source.

A development of the invention provides that for detecting the membrane acceleration an acceleration sensor arranged on the diaphragm, in particular In particular, a piezoelectric sensor or a MEMS sensor is used. In this way, it is possible to directly determine the membrane acceleration, that is to say not only indirectly from at least one other membrane state variable. To carry out the measurement of the membrane acceleration, the acceleration sensor should be arranged directly on the membrane in such a way that it moves together with it in accordance with the drive signal. In principle, any acceleration sensor can be used. However, a piezoelectronic sensor or a MEMS sensor (MEMS: microelectromechanical system) is particularly preferred. Of course, several acceleration sensors can be arranged on the membrane. In addition, at least one further acceleration sensor may be provided on a basket of the loudspeaker or on an element fixedly held relative to the basket. This serves therefore to detect an acceleration of the basket and can be used to correct the determined by means of the above-described acceleration sensor Membranistbeschleunigung. This is particularly useful when the speaker is present in an accelerated reference frame, as is the case for example when arranged in a motor vehicle. The total acceleration of the loudspeaker can be determined with the at least one further acceleration sensor. The membrane acceleration is now determined, for example, by subtracting the total acceleration from the initially measured membrane acceleration.

A development of the invention provides that the unrecognized membrane actual state variable (s) is / are determined from the at least one detected membrane actual state variable. As already stated above, not all of the membrane state variables of the final membrane state must be determined, that is to say measured. On the contrary, it is possible to detect only some of the membrane actual state quantities and to calculate the unrecorded ones of them. For this purpose, for example, a corresponding differential equation system is achieved. Basically, however, the accuracy of the Membranistzustands is greater, the more membrane actual state variables are detected. Particularly preferably, two of the membrane actual state variables, namely the membrane initial position and the membrane protein acceleration, are detected and the membrane actual velocity subsequently determined therefrom. This is possible with comparatively little computational effort. At the same time, the membrane state determined in this way is of high accuracy.

A development of the invention provides that for determining the activation signal in addition to the Membranististzustand as a membrane target position, membrane roll speed or membrane target acceleration prevailing diaphragm target state is used, which is determined from an input signal of the speaker device. The loudspeaker device is therefore initially provided with the input signal, for example from a top source or the like. This sound source can be, for example, a component of the stereo system or the car-fidelity system. From this input signal, the nominal diaphragm state is determined. The nominal diaphragm position, the nominal diaphragm speed or the diaphragm rolling acceleration are used as the nominal diaphragm state, ie only a single one of these nominal diaphragm states. This target state of the membrane is now compared with the membrane state or the membrane state variable corresponding to the membrane target state variable. This comparison results in the drive signal which is applied to the voice coil of the loudspeaker. Preferably, the membrane roll acceleration serves as a membrane target state. In this case, for example, a difference between the target diaphragm acceleration and the diaphragm acceleration, and in addition, the diaphragm stop position, the actual diaphragm speed, and the diaphragm acceleration, are input to a relationship from which the drive signal results as an output.

A development of the invention provides that a drive voltage is used as the drive signal, the from the relationship

U (t) = - (a _mll (0 - a _lsl (0) + SSA _is (0 + γν ,, is determined (t) + _"&, (/), where a = ^■

bl

such as

δ _ mL Ra> ₀ ²

= -, and

Bl L where Xj _{St is} the diaphragm position, U (t) is the voltage applied to the loudspeaker, m is the mass of the diaphragm, L is the inductance of the voice coil, R is the resistance of the loudspeaker, ω _{0 is} the natural or resonant frequency of the loudspeaker, Q is the quality of the loudspeaker , Bl the conversion ratio of electricity in power, at a time interval a _so n the membrane target acceleration a _is the Membranistbeschleunigung, v _is the Membranistgeschwindigkeit, x _is the Membranistposition and t is time. The time interval Δί corresponds to the reciprocal of the sample frequency f _s . Of course, the general relation a (t) = v (/) = x (t) holds.

In the described embodiment, therefore, the drive voltage U (t), which is time-dependent, is used as the drive signal. The above relationship is derived from the equations dx ω _η dx 2 Bl. ,

- + - + &> n x = -I (t)

dt ² Q dt ⁰ m and

RI (t) + L- + Bl- = U (t)

dt dt, where l (t) is the current of the current flowing through the speaker. If these are summarized, the relationship results

3 ³ times _a d ² times dx

a- - + ß- - + γ- + & c = U (t)

dt ¹ dt ² dt using the quantities α, β, γ and δ defined above.

The invention further relates to a loudspeaker device, in particular for carrying out the method according to one or more of the preceding claims, with at least one loudspeaker, wherein a detection device is provided for detecting at least one Membranistzustandsgröße a membrane of the loudspeaker. In this case, the loudspeaker device should be designed to detect a membrane state of the membrane comprising the membrane state variables membrane position, membrane velocity and membrane acceleration from the at least one detected state Determine Membranistzustandsgröße and directly for determining a applied to a diaphragm in operative connection with the voice coil of the loudspeaker applied drive signal. In addition to the loudspeaker, the loudspeaker device may comprise a control device which serves to determine the actuation signal, in particular from the input signal, taking into account the membrane state.

The invention further relates to a device for noise compensation, comprising a sound detection device, a control device and a loudspeaker device, wherein the sound detection device detects a sound signal of a sound source and the control unit from the sound signal determines an anti-sound signal, which is supplied to the loudspeaker device as an input signal. It is provided that the speaker device according to the above embodiments or for carrying out the method as described above is formed. By means of the device, the sound generated by the sound source can be at least largely compensated for by sound device or anti-sound signal is emitted by speaker device. For this purpose, the sound of the sound source is detected by means of the sound detection device as a sound signal. The control unit analyzes the sound signal and generates the anti-noise signal, which is subsequently provided or supplied to the loudspeaker device. Especially in such an application of the speaker device, it is of great importance that in addition to the frequency response and the phase of the anti-noise signal can be accurately reproduced. Therefore, the speaker device described above or the corresponding method is used.

A development of the invention provides that the sound source is an internal combustion engine. The internal combustion engine is usually associated with a motor vehicle. It is now the goal to reduce the sound or its intensity in an interior space and / or an exterior space of the motor vehicle, ie in an environment of the internal combustion engine. For this purpose, the device for noise compensation is used. In particular, it is provided that this is used for sound damping in or parallel to an exhaust line of the internal combustion engine. In this case, targeted anti-sound is radiated or introduced into the exhaust system. This anti-noise is to destructively superimpose the muzzle sound emitted by the exhaust line. It is therefore advantageous to use a sound source in which the sound can be adjusted in real time both in terms of its amplitude and its phase or phase shift. This means that the possibility of 0705

must be able to specify the position, speed and / or acceleration curve of the sound-generating membrane. For this reason, the above-described sound detection device or the corresponding method is used.

It is provided that the speaker of the speaker device has the detection device that detects the Membranistposition, the Membranistgeschwindigkeit and / or the Membranistbeschleunigung and forwards it to the controller. Furthermore, the anti-noise signal is supplied to the control unit as an input signal. The input signal specifies the nominal diaphragm position, the nominal diaphragm speed or the nominal diaphragm acceleration. The controller now calculates, using the input quantities and typical loudspeaker characteristics, such as the electrical resistance, the inductance, the quality, the mass of the membrane, the natural frequency and the conversion ratio, the drive signal to be supplied to the loudspeaker, which leads to the desired course of the membrane initial state. The specific drive signal is conducted, for example, via an amplifier to the loudspeaker or its voice coil. Because usually not all of the membrane actual state variables of the membrane actual state are detected, the remaining ones, ie the non-specific membrane actual state variables, are determined by the control device from the detected membrane actual state variables, for example by solving differential equations describing the movement of the membrane. Thus, control frequencies up to 50 kHz or higher can be realized.

Finally, the invention relates to an internal combustion engine of a motor vehicle with a device for noise compensation according to the preceding embodiments, wherein the internal combustion engine is the sound source.

The invention will be explained in more detail with reference to the embodiments illustrated in the drawings, without any limitation of the invention. Showing:

1 shows a cross section through a speaker of a speaker device, and

Figure 2 is a schematic representation of the speaker device. EP2013 / 000705

FIG. 1 shows an area of a loudspeaker device 1, namely a loudspeaker 2. The loudspeaker 2 consists of a membrane 3, which is suspended so as to oscillate with respect to a housing 4 of the loudspeaker 2. This is realized in particular by means of a bead 5, via which the membrane 3 is attached to a basket 6 of the housing 4. An excitation of the speaker 2 or its membrane 3 via a voice coil 7, which is arranged in a coil guide 8 of a magnetic device 9. The magnetic device 9 has at least one permanent magnet 10 and this covering pole plates 1 1. A return of the diaphragm 3 in its initial position, when the voice coil 7 is not energized, is achieved by means of a spider 12. A central recess of the membrane 3, at the edge of which the voice coil 7 acts on the membrane 3, is closed by a cap 13.

Such a loudspeaker 2 is used in the loudspeaker device 1 shown in FIG. The loudspeaker device 1 has, in addition to the loudspeaker 2, a control device 14, a first detection device 15 and a second detection device 16. The first detection device 15 is designed as a distance sensor, preferably as a laser distance sensor. The first detection device 15 is arranged stationary relative to the housing 4 of the speaker 2 and allows a measurement of the Membranististposition. By contrast, the second detection device 16 is an acceleration sensor for measuring a membrane acceleration. The second detection device 16 is arranged, for example, on the cap 13, which is displaceable together with the membrane 3. Both the specific with the first detecting means 15 _is Membranistposition x as well as the specific means of the second detector 16 _is a Membranistbeschleunigung is supplied to the control unit fourteenth This first determines, for example by means of a calculation unit 17, from the Membranistposition _is x and the Membranistbeschleunigung a _is the Membranistgeschwindigkeit _v.

The membrane _{stop position} x _jst , the membrane _{actual velocity} v _jst and the membrane _{histological acceleration} a _is t together form a membrane actual state, which is provided by the calculation unit 17 to another calculation unit 18. The membrane state thus represents an input variable of the calculation unit 18. Furthermore, an input signal via an input 19 is made available to the loudspeaker device 1. The input signal is first converted into a membrane set state, which is to be present, for example, as a membrane nominal position x _so n, membrane nominal velocity _SO ii or membrane nominal acceleration a _so n. In the previous lying case the membrane target acceleration a _so n is used as a membrane target state. This is also supplied as an input to the calculation unit 18. The calculation unit 18 calculates a drive signal in the form of a drive voltage U from its input variables, that is to say the target state of the membrane and the membrane state. This is supplied by the control device 14 to the loudspeaker 2 or its voice coil 7. With such a loudspeaker device 1, a high-precision reproduction of the input signal is possible. In particular, not only the frequency but also the phase of the input signal is reproduced very accurately.

The speaker device 1 is used for example in the context of a device for noise compensation. This additionally has a sound detection device, not shown here, by means of which a sound signal of a sound source, for example an internal combustion engine, is detected. A control device of the device (also not shown) determines from this sound signal an anti-noise signal, which is then supplied to the loudspeaker device 1 as an input signal via the input 19. By outputting the anti-noise signal by means of the loudspeaker device 1, the sound signal is at least partially canceled.

LIST OF REFERENCE NUMBERS

Speaker Setup

speaker

membrane

casing

Beading

basket

voice coil

spool guide

magnetic device

permanent magnet

pole plate

spider

cap

control unit

1. Detection

2. Detection device

calculation unit

entrance

Claims

PATENT APPLICATIONS

1 . Method for operating a loudspeaker device (1) with at least one loudspeaker (2), wherein at least one membrane actual state variable of a membrane (3) of the loudspeaker (2) is detected by a detection device (15, 16), characterized in that an IVi-membrane state of the membrane, comprising the membrane _{actual state variables} membrane _{stop position} (x _ist ), membrane _{actual velocity} (v _jst ) and membrane _{actual acceleration} (a _ist ) from which at least one detected membrane actual state variable (x _ist , aist) is determined and is used directly for determining a drive signal (U (t)) is applied to a voice coil (7) of the loudspeaker (2) in operative connection with the diaphragm (3).

A method according to claim 1, characterized in that as the at least one detected actual membrane state size, the membrane stop position (x _is ), the actual membrane velocity (v _ist ) and / or the membrane actual acceleration (a _ist ) are used.

3. The method according to any one of the preceding claims, characterized in that for detecting the Membranistposition (x _is ), a distance sensor (15), in particular an optical distance sensor, preferably a laser distance sensor, as a detection device (15) is used.

4. The method according to any one of the preceding claims, characterized in that for detecting the Membranistbeschleunigung (a _is ) on the membrane (3) arranged acceleration sensor, in particular a piezoelectric sensor or a MEMS sensor, as detection means (16) is used.

5. The method according to any one of the preceding claims, characterized in that from the at least one detected Membranistzustandsgröße (x _is t, a _is ), the unrecorded (n) Membranistzustandsgröße (s) (v _ist ) is / are determined.

6. The method according to any one of the preceding claims, characterized in that for determining the drive signal (U (t)) in addition to the Membranistzustand as a diaphragm target position (x _so n), membrane target speed (v _so n) or membrane Ransollbeschleunigung (a _so n) prevailing diaphragm target state is used, which is determined from an input signal of the speaker device (1).

7. The method according to any one of the preceding claims, characterized in that as a drive signal (U (t)), a drive voltage is used, which from the relationship

U (t) = - (a _wll (/) - a _isl (/)) + ßa _is () + yv _lsl (t) + &", (/) is determined, where a =

Loudspeaker device (1), in particular for carrying out the method according to one or more of the preceding claims, having at least one loudspeaker (2), detection means (15, 16) for detecting at least one membrane actual state variable of a membrane (3) of the loudspeaker (2) characterized in that the speaker means (1) is adapted to include a membrane state of the membrane (3) comprising the membrane state variables membrane stop position (x _ist ), membrane velocity (v _ist ), and membrane acceleration (a _is ) from the at least one detected membrane state quantity (x _is , a _is t) to be determined and used directly for determining a drive signal (U (t)) applied to a voice coil (7) of the loudspeaker (2) in operative connection with the diaphragm (3).

Apparatus for noise compensation, comprising a sound detection device, a control device and a loudspeaker device (1), wherein the sound detection device detects a sound signal of a sound source and the control unit determines from the sound signal an anti-noise signal which is supplied as an input signal to the loudspeaker device (1), characterized in that the speaker device (1) according to claim 8 or for carrying out the method according to one or more of claims 1 to 7 is formed. 10. The device according to claim 9, characterized in that the sound source is an internal combustion engine.