An active noise cancellation system for reducing, at a listening position, the power of a noise signal being radiated from a noise source to the listening position, the system comprising: an adaptive filter receiving a reference signal (x e [n]) representing the noise signal and comprising an output providing a compensation signal (y[n]); at least one acoustic actuator radiating the compensation signal to the listening position; a microphone arranged at the listening position, the microphone providing a residual error signal (e[n]); a filter connected downstream to the adaptive filter and providing an estimation (y"[n]) of the compensation signal at the listening position (y'[n]); means for subtracting the estimated compensation signal at the listening position (y"[n]) from the error signal (e[n]) thus providing an estimated noise signal at the listening position (d'[n]); characterised by a signal processing device (41, 42, 43, 50) that comprises: signal processing units (41, 42, 43) receiving, as input signals, the error signal (e[n]), the estimated compensation signal at the listening position (y"[n]), and the estimated noise signal at the listening position (d'[n]), respectively, each signal processing unit (41, 42, 43) being configured to calculate at least one signal parameter {E{e[n] 2}, E{y"[n] 2}, E(d'[n] 2}) of their respective input signal (e[n], y"[n], d'[n]); and a decider unit connected downstream to the signal processing units (41, 42, 43), the decider unit being configured to evaluate the signal parameters (E{e[n] 2}, E{y"[n] 2}, E{d'[n] 2}) for assessing the stability of the adaptive filter. an adaptive filter receiving a reference signal (x e [n]) representing the noise signal and comprising an output providing a compensation signal (y[n]); at least one acoustic actuator radiating the compensation signal to the listening position; a microphone arranged at the listening position, the microphone providing a residual error signal (e[n]); a filter connected downstream to the adaptive filter and providing an estimation (y"[n]) of the compensation signal at the listening position (y'[n]); means for subtracting the estimated compensation signal at the listening position (y"[n]) from the error signal (e[n]) thus providing an estimated noise signal at the listening position (d'[n]); characterised by a signal processing device (41, 42, 43, 50) that comprises: signal processing units (41, 42, 43) receiving, as input signals, the error signal (e[n]), the estimated compensation signal at the listening position (y"[n]), and the estimated noise signal at the listening position (d'[n]), respectively, each signal processing unit (41, 42, 43) being configured to calculate at least one signal parameter {E{e[n] 2}, E{y"[n] 2}, E(d'[n] 2}) of their respective input signal (e[n], y"[n], d'[n]); and a decider unit connected downstream to the signal processing units (41, 42, 43), the decider unit being configured to evaluate the signal parameters (E{e[n] 2}, E{y"[n] 2}, E{d'[n] 2}) for assessing the stability of the adaptive filter. signal processing units (41, 42, 43) receiving, as input signals, the error signal (e[n]), the estimated compensation signal at the listening position (y"[n]), and the estimated noise signal at the listening position (d'[n]), respectively, each signal processing unit (41, 42, 43) being configured to calculate at least one signal parameter {E{e[n] 2}, E{y"[n] 2}, E(d'[n] 2}) of their respective input signal (e[n], y"[n], d'[n]); and a decider unit connected downstream to the signal processing units (41, 42, 43), the decider unit being configured to evaluate the signal parameters (E{e[n] 2}, E{y"[n] 2}, E{d'[n] 2}) for assessing the stability of the adaptive filter.