A system comprising a receiver for receiving an amplitude modulated ultrasonic signal from a transmitter to form an analysis signal on the basis of the received signal; the receiver comprising: - a first receiving element (9.1) for receiving the amplitude modulated ultrasonic signal from the transmitter; - a first detector (9.7) for demodulating the signal received by the first receiving element (9.1) to form a first demodulated analysis signal; - a second receiving element (9.2) for receiving the amplitude modulated ultrasonic signal from the transmitter; - a second detector (9.8) for demodulating the signal received by the second receiving element (9.2) to form a second demodulated analysis signal; and - a phase detector (9.9) for providing an indication on the basis of a phase difference between said first and second demodulated analysis signals; - an analysing element for analysing said indication to determine the heading angle of an object with reference to the transmitter and to form an analysis signal indicative of the determined heading angle of the object, wherein the analysing element comprises: - an input for inputting said indication; - a first scaling element (11.1) configured for scaling the magnitude of said indication by a first scaling factor; - a second scaling element (11.4); - a summing element (11.2) configured for summing the scaled indication provided by the first scaling element (11.1) and a scaled feedback signal from the second scaling element thereby outputting an estimate of the heading angle of the object with reference to the transmitter; - a buffer (11.3) configured for buffering output estimate from the summing element (11.2) at different moments of time, thereby buffering estimates of the heading angle of the object, and for providing a feedback signal, wherein the second scaling element (11.4) is configured for scaling the magnitude of the feedback signal by a second scaling factor thereby producing the scaled feedback signal; and - a control element (11.5) configured to adjust said first and second scaling factors of the first scaling element (11.1) and the second scaling element (11.4) on the basis of changes in the estimated heading angle of the object; wherein the system further comprises an audio processing device configured to use said analysis signal to delay one of a first signal formed by the audio processing device and a second signal formed by the audio processing device; wherein said analysing element is adapted to compare said indication with at least one or more of said buffered estimates of the heading angle of the object with reference to the transmitter in determining a reliability of the indication. - a first receiving element (9.1) for receiving the amplitude modulated ultrasonic signal from the transmitter; - a first detector (9.7) for demodulating the signal received by the first receiving element (9.1) to form a first demodulated analysis signal; - a second receiving element (9.2) for receiving the amplitude modulated ultrasonic signal from the transmitter; - a second detector (9.8) for demodulating the signal received by the second receiving element (9.2) to form a second demodulated analysis signal; and - a phase detector (9.9) for providing an indication on the basis of a phase difference between said first and second demodulated analysis signals; - an analysing element for analysing said indication to determine the heading angle of an object with reference to the transmitter and to form an analysis signal indicative of the determined heading angle of the object, - an input for inputting said indication; - a first scaling element (11.1) configured for scaling the magnitude of said indication by a first scaling factor; - a second scaling element (11.4); - a summing element (11.2) configured for summing the scaled indication provided by the first scaling element (11.1) and a scaled feedback signal from the second scaling element thereby outputting an estimate of the heading angle of the object with reference to the transmitter; - a buffer (11.3) configured for buffering output estimate from the summing element (11.2) at different moments of time, thereby buffering estimates of the heading angle of the object, and for providing a feedback signal, - a control element (11.5) configured to adjust said first and second scaling factors of the first scaling element (11.1) and the second scaling element (11.4) on the basis of changes in the estimated heading angle of the object;