ANC noise active control audio headset with prevention of the effects of a saturation of the feedback microphone signal

1. An audio headset, comprising:

two earphones ( 10 ) each including a transducer ( 18 ) for the sound reproduction of an audio signal to be reproduced, said transducer being housed in an ear acoustic cavity ( 22 );

at least one microphone adapted to deliver a picked-up signal including an acoustic noise component;

a movement sensor ( 64 ) mounted on at least one of the earphones and adapted to deliver an accelerometer signal; and

a digital signal processor, DSP, ( 50 ) comprising:

a mixer, receiving as an input a signal coming from the microphone as well as said audio signal to be reproduced, and delivering as an output a signal adapted to pilot the transducer ( 18 ); and

an anti-saturation module adapted to analyse concurrently i) the microphone signal delivered by the microphone and ii) the accelerometer signal delivered by the movement sensor ( 64 ), and to verify whether current characteristics of these microphone and accelerometer signals fulfil or not a first set of predetermined criteria,

characterized in that:

the headset comprises an ANC active noise control system;

the microphone is an internal ANC microphone ( 28 ) placed inside the acoustic cavity ( 22 );

the DSP ( 50 ) comprises:

a closed-loop feedback branch ( 36 ), comprising a feedback ANC filter ( 54 ) adapted to apply a filtering transfer function (H FB ) to the signal picked up by the internal ANC microphone ( 28 ); and

the mixer, which receive as an input the signal delivered by the feedback branch at the output of the feedback ANC filter ( 54 ) as well as said audio signal to be reproduced, and deliver as an output said signal adapted to pilot the transducer ( 18 ); and

the DSP further comprises a prevention module for preventing the effects on the feedback branch of a saturation of the signal delivered by the internal microphone ( 28 ), comprising:

the anti-saturation module adapted to analyse concurrently i) the microphone signal delivered by the microphone ( 28 ) and ii) the accelerometer signal delivered by the movement sensor ( 64 ), and to verify whether current characteristics of these microphone and accelerometer signal fulfil or not a first set of predetermined criteria; and

in the feedback branch upstream from the feedback ANC filter ( 54 ), a feedback anti-saturation filter ( 70 ) selectively switchable as a function of the result of the verification of the first set of criteria.

2. The audio headset according to claim 1 , wherein:

the feedback anti-saturation filter ( 70 ) is one between a plurality of selectively switchable, pre-configured filters; and

the DSP ( 50 ) further comprises:

the anti-saturation module adapted to select one of the pre-configured anti-saturation filters as a function of the result of the verification of the first set of criteria.

3. The audio headset according to claim 1 , wherein:

the DSP ( 50 ) further comprises:

an equalization branch, comprising an equalization filter ( 58 ) adapted to apply an equalization transfer function (H EQ ) to the audio signal to be reproduced (M) before application of the latter to the mixer; and

in the equalization branch, upstream from the equalization filter ( 58 ), an equalization anti-saturation filter ( 72 ) that is selectively switchable at the same time as the feedback anti-saturation filter ( 70 ).

4. The audio headset according to claim 1 , wherein:

the feedback anti-saturation filter ( 72 ) is one between a plurality of selectively switchable, pre-configured equalization filters; and

the DSP ( 50 ) further comprises:

the anti-saturation module adapted to select one of the pre-configured equalisation filters as a function of the result of the verification of the first set of criteria.

5. The audio headset according to claim 1 , wherein the current characteristics of the accelerometer signal comprise a value of energy (Rms acc ) of the accelerometer signal, and the predetermined criteria comprise a threshold (Threshold_a) to which is compared said value of energy.

6. The audio headset according to claim 5 , wherein the current characteristics of the microphone signal comprise values of energy (Rms 1 , Rms 2 . . . ) of the microphone signal in a plurality of respective frequency bands (Filter 1 , Filter 2 . . . ), and the predetermined criteria comprise a series of respective thresholds (Threshold 1 , Threshold 2 . . . ThresholdN) to which are compared said energy values of the microphone signal if the value of energy (Rms acc ) of the accelerometer signal exceeds said threshold (Threshold_a).

7. The audio headset according to claim 1 , wherein:

the feedback ANC filter ( 54 ) is one between a plurality of selectively switchable, pre-configured feedback ANC filters; and

the DSP ( 50 ) further comprises:

an active noise control module for analysing the signal delivered by the internal microphone, adapted to verify whether current characteristics of the signal delivered by the internal microphone fulfil or not a second set of predetermined criteria; and

a selection module, adapted to select one of the pre-configured feedback ANC filters as a function of the result of the verification of the second set of criteria.

8. The audio headset according to claim 7 , wherein:

the DSP ( 50 ) further comprises:

an equalization branch, comprising an equalization filter ( 58 ) adapted to apply an equalization transfer function (H EQ ) to the audio signal to be reproduced (M) before application of the latter to the mixer;

the equalization filter ( 58 ) is one between a plurality of selectively switchable, pre-configured equalization filters, and

the selection module are also adapted to select one of the pre-configured equalization filters as a function of the current selected feedback ANC filter.