The signal processing is performed by the microprocessor in real time and taking into account the individual preferences of the user (for example, increasing bass for better speech perception in noisy environments, or selective amplification of high frequencies for people with reduced sensibility to this range). The microprocessor automatically analyzes the nature of the external background noise and adapts the signal processing to the specific conditions (as well as to its change, for example, when the user goes outside from the building).