Method and system for acoustic shock detection and application of said method in hearing devices

1. A method for detecting acoustic shock in an audio input signal (s(t)), comprising the steps of

monitoring the input signal (s(t)) in the time-domain, thereby

detecting a signal floor (Sn),

detecting a peak level of the input signal (L),

detecting an attack time (t 1 -t 0 ) of the input signal as a time difference between a time (t 1 ) when the peak level of the input signal (L) is detected and a time (t 0 ) when the acoustic shock being detected begins,

determining a shock contrast level (dL) as a difference between the peak level (L) and the signal floor (Sn),

determining a shock index (SI) based on a shock index normalization constant (σ), the shock contrast level (dL) and the attack time (t 1 -t 0 ),

comparing the shock contrast level (dL) and the shock index (SI) with respective thresholds (MCL; MSI) and

indicating an acoustic shock if one or both of said thresholds (MCL; MSI) are exceeded.

2. Method according to claim 1 characterized in that the signal floor (Sn) is obtained through a signal processing method catching up the non-transient signal change over time.

3. Method according to claim 2 characterized in that the signal processing method is provided by a lowpass filter or a fast smooth signal processing.

4. Method according to claim 1 characterized in that the signal floor (Sn) is derived from the following formula

Sn

=

10

⁢

⁢

log

[

1

T

0

⁢

∫

t

-

T

0

t

⁢



s

⁡

(

t

)

⁢

ⅆ

t

]

5. Method according claim 4 characterized in that the averaging of s(t) will be performed for a short time period T 0 of about 4 ms or less.

6. A method according to claim 1 characterized in that the shock index (SI) is derived from the following formula:

SI

=

σ

⁢

⁢

L

-

S

n

t

1

-

t

0

wherein σ is the coefficient for shock index normalization.

7. A method according to claim 6 , characterized in that the coefficient for shock index normalization (σ) is pre-defined for typical shock events or is determined by a self-learning process.

8. A method according to claim 1 , characterized in that it further comprises the step of

applying anti-shock gain reduction (g(t)) when a shock event has been indicated.

9. A method according to claim 8 characterized in that an anti-shock gain reduction (g(t)) is applied in time-domain to the input signal (s(t)) resulting in a new signal (x(t)) with completed anti-shock processing.

10. A method according to claim 9 characterized in that the anti-shock gain reduction (g(t)) is applied to the input signal (s(t)) after adding signal delay.

11. A method according to claim 8 characterized in that an anti-shock gain reduction (g(t)) is applied in the frequency-domain.

12. A method according to claim 8 characterized in that the anti-shock gain reduction (g(t)) is applied in different frequency bands independently.

13. A method according to claim 8 characterized in that additionally different activation functions are selected according to the shock type or a user preference.

14. Application of the method according to claim 1 for operating a hearing device.

15. An audio signal processing system for detecting acoustic shock in a audio input signal s(t) comprising at least one shock detection module ( 12 ) with means that permits the

monitoring the input signal (s(t)) in a time-domain, thereby

detecting a signal floor (Sn),

detecting a peak level of the audio input signal (L),

detecting an attack time (t 1 -t 0 ) of the input signal as a time difference between a time (t 1 ) when the peak level of the input signal (L) is detected and a time (t 0 ) when the acoustic shock being detected begins,

determining a shock contrast level (dL) as a difference between the peak level (L) and the signal floor (Sn),

determining a shock index (SI) based on a shock index normalization constant (σ), the shock contrast level (dL) and the attack time (t 1 -t 0 ),

comparing the shock contrast level (dL) and the shock index (SI) with respective thresholds (MCL; MSI) and

indicating an acoustic shock if one or both of said thresholds (MCL; MSI) are exceeded.

16. A system according to claim 15 characterized in that it further comprises at least one managing module ( 13 ) with means that permits applying anti-shock gain reduction (g(t)) when a shock event has been indicated.

17. A system according to claim 16 characterized in that the managing module ( 13 ) is working in the time-domain.

18. A system according to claim 16 characterized in that the managing module ( 13 ) is working in the frequency-domain.

19. A method for detecting acoustic shock in an audio input signal (s(t)), comprising the steps of

monitoring the input signal (s(t)) in a time-domain, thereby

detecting a signal floor (Sn),

detecting a peak level of the audio input signal (L),

detecting an attack time of the input signal (t 1 -t 0 ),

determining a shock contrast level (dL) as a difference between the peak level (L) and the signal floor (Sn),

determining a shock index (SI) by use of a shock index normalization constant (σ), wherein the shock index (SI) is derived as follows:

SI

=

σ

⁢

L

-

S

n

t

1

-

t

0

wherein σ is the coefficient for shock index normalization

comparing the shock contrast level (dL) and the shock index (SI) with respective thresholds (MCL; MSI) and

indicating an acoustic shock if one or both of said thresholds (MCL; MSI) are exceeded.

20. A method according to claim 8 , wherein the anti-shock gain reduction (g(t)) is dependent on at least one of a shock duration (T), the shock contrast level (dL) and the shock index (SI).

21. A system according to claim 16 , wherein the anti-shock gain reduction (g(t)) to be applied by the means that permits applying anti-shock gain reduction is dependent on at least one of the shock duration (T), the shock contrast level (dL) and the shock index (SI).