Experimental design and representative single subject results. (a): Schematic representation of the stimulus sequence with notch-filtered noise (NFN) of 3 s duration and the following test stimulus (TS) of 150 ms duration with an inter-stimulus interval of 500 ms. (b): Amplitude spectrum of the 3 s NFN measured at the ear-piece. Differences in frequency domain between the TS and the low-pass slope of the NFNs are: 1/6 octave (NFN1), 2/6 octave (NFN2), 3/6 octave (NFN3), 4/6 octave (NFN4), and 5/6 octave (NFN5). Center frequencies of the stop-band regions are: 1260 (NFN1), 1122 (NFN2), 1000 (NFN3), 891 (NFN4), and 794 Hz (NFN5). All NFNs had one-octave stop-band frequency. The bandwidths of the neighbouring dotted vertical lines are 1/6 octave. (c): Superposition of the auditory evoked magnetic fields (AEFs) from all magnetic sensors as recorded in one representative subject. AEFs elicited by the test stimulus (TS) following each NFN (NFN1 to NFN5).