An audio processing system for processing an input sound comprising a target signal (x(n)) to an output sound, the audio processing system comprising • an input transducer comprising a microphone for converting an input sound to an electric input signal and defining an input side, • an output transducer for converting a processed electric output signal to an output sound and defining an output side, • a forward path being defined between the input transducer and the output transducer, and comprising a signal processing unit (G(z,n)) adapted for processing an input signal (e(n)) originating from the electric input signal and to provide a processed output signal (u(n), y(n)) the processed electric output signal being derived from the processed output signal, • an electric feedback loop from the output side to the input side comprising ∘ a feedback path estimation unit (Algorithm, Fh(z,n)) for estimating an acoustic feedback transfer function (F(z,n)) from the output transducer to the input transducer, said feedback path estimation unit comprising an adaptive filter comprising a variable filter part (Fh(z,n)) and an algorithm part (Algorithm) for updating filter coefficients of the variable filter part, and ∘ an enhancement unit (Enhancement; Eh_e, Eh_u; Enh_e, Enh_u) for extracting characteristics of an electric signal of the forward path and providing a noise signal estimate output (es(n)), wherein the enhancement unit comprises a second adaptive filter (C(z,n)); and • a probe signal generator (Probe signal) for generating a probe signal (us(n)) contributing to the estimation of the feedback transfer function (F(z,n)), the probe signal generator being adapted to provide that the probe signal has predefined characteristics, wherein the enhancement unit (Enhancement; Eh_e, Eh_u; Enh_e, Enh_u) is adapted to provide said noise signal estimate output (es(n)) based on said predefined characteristics of the probe signal (us(n)); and wherein the algorithm part (Algorithm) of the adaptive filter of the feedback path estimation unit is adapted to base the update at least partly on said noise signal estimate output (es(n)) from the enhancement unit in the estimation of the acoustic feedback transfer function, CHARACTERIZED IN THAT the algorithm part of the adaptive filter of the feedback path estimation unit comprises a step length control block for controlling a step length of the algorithm part in a given frequency region, and wherein the step length control block receives a control input from the probe signal generator. • an input transducer comprising a microphone for converting an input sound to an electric input signal and defining an input side, • an output transducer for converting a processed electric output signal to an output sound and defining an output side, • a forward path being defined between the input transducer and the output transducer, and comprising a signal processing unit (G(z,n)) adapted for processing an input signal (e(n)) originating from the electric input signal and to provide a processed output signal (u(n), y(n)) the processed electric output signal being derived from the processed output signal, • an electric feedback loop from the output side to the input side comprising ∘ a feedback path estimation unit (Algorithm, Fh(z,n)) for estimating an acoustic feedback transfer function (F(z,n)) from the output transducer to the input transducer, said feedback path estimation unit comprising an adaptive filter comprising a variable filter part (Fh(z,n)) and an algorithm part (Algorithm) for updating filter coefficients of the variable filter part, and ∘ an enhancement unit (Enhancement; Eh_e, Eh_u; Enh_e, Enh_u) for extracting characteristics of an electric signal of the forward path and providing a noise signal estimate output (es(n)), wherein the enhancement unit comprises a second adaptive filter (C(z,n)); and ∘ a feedback path estimation unit (Algorithm, Fh(z,n)) for estimating an acoustic feedback transfer function (F(z,n)) from the output transducer to the input transducer, said feedback path estimation unit comprising an adaptive filter comprising a variable filter part (Fh(z,n)) and an algorithm part (Algorithm) for updating filter coefficients of the variable filter part, and ∘ an enhancement unit (Enhancement; Eh_e, Eh_u; Enh_e, Enh_u) for extracting characteristics of an electric signal of the forward path and providing a noise signal estimate output (es(n)), wherein the enhancement unit comprises a second adaptive filter (C(z,n)); and • a probe signal generator (Probe signal) for generating a probe signal (us(n)) contributing to the estimation of the feedback transfer function (F(z,n)), the probe signal generator being adapted to provide that the probe signal has predefined characteristics,