Fig. 6. Calculated influence of the stimulus filters and the roving level on the frequency centroid and the level of the recorded calls (mean ± s.d. of 9500 calls for Bat 4 and 15055 calls for Bat 5). (A) The stimulus filters, going from lowpass (–6 dB/octave) to highpass (+6 dB/octave), increased the frequency centroid of the recorded calls by about 5 kHz. (B) The stimulus filters, going from lowpass (–6 dB/octave) to highpass (+6 dB/octave), increased the r.m.s. level of the recorded calls by 2–3 dB SPL. (C) Increasing roving levels, i.e. higher overall levels, reduced the frequency centroid of the recorded calls by about 2 kHz.