Method of operating a hearing aid system and a hearing aid system

1. A method of operating a hearing aid system comprising the steps of:

identifying a receiver type of the hearing aid system,

providing a threshold frequency based on the identified receiver type,

measuring the electrical impedance of a receiver of the hearing aid system for a range of frequencies hereby providing a measured receiver impedance spectrum,

determining at least one of a peak frequency and a valley frequency from the measured receiver impedance spectrum,

triggering an action in response to a frequency threshold test applied to the determined peak frequency or valley frequency indicating that the peak frequency or valley frequency exceeds the threshold frequency, wherein

the threshold frequency is selected such that the action is triggered when a sound output of a hearing aid is at least partially congested.

2. The method according to claim 1 , wherein the step of identifying the receiver type of the hearing aid system is carried out manually by a hearing care professional or automatically by the hearing aid system based on a comparison of at least one characteristic from a measured receiver impedance spectrum with corresponding values for a range of receiver types.

3. The method according to claim 1 , wherein the step of providing a threshold frequency based on the identified receiver type comprises the further steps of:

determining the threshold frequency using a database holding information on at least one statistical characteristic of the receiver impedance spectrum for the identified receiver type.

4. The method according to claim 3 , wherein the statistical characteristic is selected from a group comprising average threshold frequency and average frequency shift as a function of sound output congestion.

5. The method according to claim 1 , wherein the step of providing a threshold frequency comprises the further steps of:

determining a reference peak- or valley frequency based on a receiver impedance spectrum measured during hearing aid system manufacturing or during hearing aid system fitting,

determining the threshold frequency by using the determined reference peak- or valley frequency and by using a database holding information on an average peak frequency shift and/or valley frequency shift as a function of congestion of a sound output.

6. The method according to claim 1 , wherein the step of determining at least one of peak frequency and a valley frequency from the measured receiver impedance spectrum comprises the further steps of:

using a database to determine, as a function of the identified receiver type, whether the step of triggering an action should rely on a peak frequency or a valley frequency exceeding the threshold frequency.

7. The method according to claim 1 , wherein the predetermined threshold is in the range between 100 and 5000 Hz.

8. The method according to claim 1 , wherein the step of providing a measured receiver impedance spectrum comprises the step of selecting among a range of measurement resistors based on the identified receiver type of the hearing aid system.

9. The method according to claim 1 , wherein the triggered action is selected from a group comprising: issuing a visual or an acoustic alert, logging data related to the exceeded threshold in the hearing aid system, and providing data related to the exceeded threshold to an external server.

10. The method according to claim 1 , wherein an acoustic alert is only issued when a speech detector determines that no speech is present in the sound environment.

11. The method according to claim 1 , wherein the step of measuring the electrical impedance of a receiver of the hearing aid system for a range of frequencies is carried out in response to a powering up of the hearing aid system, in response to a user initiated change of a hearing aid setting or in response to a user requesting it using a user interface of the hearing aid system.

12. The method according to claim 1 , wherein the step of measuring the electrical impedance of a receiver of the hearing aid system for a range of frequencies comprises the step of:

adapting the strength of a measurement signal used for measuring the electrical impedance, in at least one frequency range, in dependence on the hearing deficit of the hearing system user such that the measurement signal is not audible for the hearing system user.

13. The method according to claim 12 , wherein the step of measuring the electrical impedance of a receiver of the hearing aid system for a range of frequencies comprises the step of:

increasing the strength of a measurement signal used for measuring the electrical impedance, in at least one frequency range, in dependence on the hearing deficit of the hearing system user such that the signal-to-noise is improved while the measurement signal is not audible for the hearing system user.

14. The method according to claim 1 , wherein the step of providing a measured receiver impedance spectrum is carried out using a voltage supply adapted to provide a voltage, for driving an H-bridge output stage of a hearing aid of the hearing aid system, that is at least 30 dB lower than the voltage employed in normal operation mode.