Sound transducer and method for operating the sound transducer

1. A sound transducer comprising:

a carrier body;

a first piezoelectric element comprising:

first external electrodes configured to generate an acoustic signal from an electrical signal or vice versa, and

at least one second external electrode, wherein the second external electrode is separately controllable from the first external electrodes in order to set electro-acoustic properties of the sound transducer;

a diaphragm configured to generate and/or receive the acoustic signal,

wherein the diaphragm is mounted in a vibratable manner on the carrier body,

wherein the first piezoelectric element is configured to convert the electrical signal into a deformation of the diaphragm or vice versa; and

a second piezoelectric element, on which the second external electrode is arranged,

wherein the second piezoelectric element forms a stacked arrangement with the first piezoelectric element, and

wherein the stacked arrangement is fixed to one side of the diaphragm.

2. The sound transducer according to claim 1 , wherein the first and second piezoelectric elements comprise a piezoceramic.

3. The sound transducer according to claim 1 , wherein the second piezoelectric element is fixed to the carrier body, integrated in the carrier body or forms the carrier body.

4. The sound transducer according to claim 1 , wherein the second piezoelectric element is connected only to a supporting region of the diaphragm, the supporting region being located at an edge of the diaphragm.

5. The sound transducer according to claim 1 , wherein the second piezoelectric element is designed to radially expand or contract when a voltage is applied, and wherein a deformation is transferred to the diaphragm such that a rigidity of the diaphragm changes.

6. The sound transducer according to claim 1 , wherein the first piezoelectric element is fastened to the diaphragm.

7. The sound transducer according to claim 1 , wherein the second piezoelectric element is coupled to the diaphragm via a coupling element.

8. The sound transducer according to claim 1 , wherein the diaphragm is formed in one part with the carrier body.

9. A method for operating a sound transducer, wherein the sound transducer comprises a first piezoelectric element having first external electrodes configured to generate an acoustic signal from an electrical signal or vice versa, and at least one second external electrode, wherein the second external electrode is separately controllable from the first external electrodes in order to set electro-acoustic properties of the sound transducer, the method comprising:

controlling the second external electrode in such a manner that the electro-acoustic properties of the sound transducer are set in a specific manner, wherein the controlling the second external electrode comprises changing an anti-resonant frequency of the sound transducer after emitting the acoustic signal.

10. The method according to claim 9 , wherein controlling the second external electrode comprises compensating an environment-related or age-related change in a resonant frequency and/or a Q factor of the sound transducer.

11. The method according to claim 9 , further comprising simultaneously controlling the first external electrodes thereby generating the acoustic signal at a resonant frequency.

12. The method according to claim 9 , wherein controlling the second external electrode comprises shifting a resonant frequency of the sound transducer to a desired value.

13. The method according to claim 9 , wherein controlling the second external electrode comprises a low-resistance termination, a high-resistance termination, applying an electrical DC voltage or applying an electrical AC voltage.

14. An arrangement comprising:

a plurality of sound transducers according to claim 1 ,

wherein the second external electrodes of the sound transducers are differently controllable from one another.

15. The arrangement according to claim 14 , wherein the arrangement is a parking aid for a motor vehicle.

16. A method for operating the arrangement according to claim 14 , the method comprising:

differently controlling at least one of the second external electrodes than another of the second external electrodes.

17. The method according to claim 16 , wherein differently controlling the at least one of the second external electrodes than another of the second external electrodes comprises ensuring that the acoustic signals emitted by the sound transducers are distinguishable.

18. A sound transducer comprising:

a carrier body;

a first piezoelectric element comprising:

first external electrodes configured to generate an acoustic signal from an electrical signal or vice versa, and

at least one second external electrode, wherein the second external electrode is separately controllable from the first external electrodes in order to set electro-acoustic properties of the sound transducer;

a diaphragm configured to generate and/or receive the acoustic signal,

wherein the diaphragm is mounted in a vibratable manner on the carrier body,

wherein the first piezoelectric element is designed to convert the electrical signal into a deformation of the diaphragm or vice versa; and

a second piezoelectric element, on which the second external electrode is arranged,

wherein the second piezoelectric element is fixed to the carrier body, integrated in the carrier body or forms the carrier body.

19. A method for operating an arrangement of a plurality of sound transducers, wherein each of the sound transducers comprises a first piezoelectric element having first external electrodes for generating an acoustic signal from an electrical signal or vice versa and a second piezoelectric element on which a second external electrode is arranged, the method comprising:

controlling the second external electrodes in such a manner that electro-acoustic properties of each respective sound transducer are set in a specific manner, in which at least one of the second external electrodes is controlled differently than another one of the second external electrodes and in which the different controls ensure that the acoustic signals emitted by the sound transducers at the same time are distinguishable.

20. The sound transducer according to claim 1 , wherein the first piezoelectric element and the second piezoelectric element are electrically connected in series, or wherein the connection corresponds to an electrical parallel circuit.

21. A method for operating the sound transducer of claim 1 , the method comprising:

controlling the second piezoelectric element to optimize the sound transducer for operation at long distances or at short distances.

22. A method for operating the sound transducer of claim 1 , the method comprising:

controlling the second piezoelectric element to radially expand or contract when a voltage is applied, wherein the deformation is transferred to the diaphragm such that a rigidity of the diaphragm and therefore a resonant frequency, anti-resonant frequency and/or Q factor of the diaphragm changes.