Method and device for acoustically detecting a malfunction of a motor having an active noise control

1. A method for acoustically detecting at least one malfunction of an engine, said method comprising:

processing a primary noise Po generated by said engine by an active noise control system, said active noise control system comprising noise reduction targets receiving in a region the primary noise and configured to identify in said primary noise an acoustic signature corresponding to a malfunction;

emitting an acoustic signal Pc towards said noise reduction targets, said acoustic signal Pc being produced by at least one actuator and linked by a transfer function H to a signal Y for said at least one actuator, said signal Y being produced by said active noise control system;

acquiring said signal Y from an output of the active noise control system by a detector for acoustically detecting at least one malfunction of an engine, wherein said signal Y is acquired using inductive sensors on control cables of the at least one actuator;

identifying the possible occurrence of the malfunction using said detector by utilizing the knowledge of the signal Y and of the transfer function H used by the active noise control system without using a signal being produced by an acoustic sensor; and

emitting an alarm signal when a malfunction is identified.

2. The method according to claim 1 , wherein the active noise control system evaluates changes in the transfer function H over time which are the subject of an acquisition and are used by the identification step.

3. The method according to claim 1 , wherein the signal Y is formed by a set of control signals of the actuators of the active control system.

4. The method according to claim 1 , wherein the detector reconstructs a representation of the acoustic signal Pc by matrix combination between the signal Y and the transfer function H and identifies therein the possible presence of the acoustic signature of said malfunction by comparison with engine noise without any malfunctions.

5. The method according to claim 1 , wherein said identifying the possible occurrence of the malfunction is implemented on a limited set of characteristic frequencies, and comprises an intermediate step of extracting signals originating from said acquiring said signal Y which provides indicators reduced to the components Y and H for the frequencies specific to the identification of the malfunction noise at said characteristic frequencies.

6. The method according to claim 1 , wherein said step of identifying the possible occurrence of the malfunction is carried out remotely, outside of an installation comprising the engine.

7. The method according to claim 1 , wherein the malfunction is identified when the signal Y and/or the transfer function changes over the time.

8. A detector for acoustically detecting at least one malfunction of an engine, the engine generating a primary noise Po, which device is arranged to be used in the presence of an active noise control system which emits, towards noise reduction targets, an acoustic signal Pc which is produced by at least one actuator and is linked by a transfer function H to a control signal Y for said at least one actuator, which signal Y is produced by said active noise control system, said malfunction having an acoustic signature which can be identified in the primary noise Po at the noise reduction targets, the detector comprising:

means for acquiring the signal Y which is produced by the active noise control system wherein the means for acquiring the signal Y comprises inductive sensors on the control cables of the actuators which are capable of receiving the control signals; and

monitoring means which is arranged to identify the possible occurrence of the malfunction from the signal Y and the knowledge of the transfer function H used by the active noise control system without using a signal being produced by an acoustic sensor, and to emit an alert message when a malfunction is identified.

9. The device according to claim 8 , wherein said means for acquiring the signal Y is arranged to detect, using the active noise control system, changes in the transfer function that it is evaluating over time, and wherein the monitoring means is arranged to use said changes in the transfer function.

10. The device according to claim 8 , wherein the device is configured to extract indicators reduced to the components of the signal Y and the transfer function H for the frequencies specific to the identification of the malfunction noise over a limited set of characteristic frequencies.

11. The device according to claim 8 , wherein the monitoring means is remote from an installation comprising the engine.

12. A turbine engine capable of generating a primary noise Po, the turbine engine comprising:

an active noise control system elaborating a transfer function H and a signal Y in order to generate an acoustic signal Pc giving an estimation of the primary noise Po; and

a detector configured to acoustically detect at least one malfunction of an engine cooperating with the active noise system, said detector being configured to use the transfer function H and the signal Y output by the active noise control system so as to reconstitute the primary noise Po and extract at least a malfunction acoustic signature without using a signal being produced by an acoustic sensor;

wherein the detector is further configured to acquire said signal Y using inductive sensors on control cables that communicatively couple the active noise control system to at least one actuator for generating the acoustic signal Pc.