Fig. 4. Mean hearing thresholds of Perca fluviatilis (solid lines) under laboratory conditions (baseline) and in the presence of the different ambient noise types. Broken lines show the cepstrum-smoothed sound power spectra of the corresponding habitat noise (Fig. 1 shows the absolute amplitude spectra). DR, Danube river; TS, Triesting stream; BW, backwater; LN, Lake Neusiedl.