The calls of Pipa carvalhoi were recorded with a hydrophone and analysed with a sound level meter, and the data compared with those measured in air. Three types of calls can be differentiated in males (females are not able to produce calls):
The sound pressure level of trills reached 120 dB, that of clicks 90 dB. Corresponding data for the sound measured in air are 62 and 41 dB. Experiments with wall covers suppressing resections suggest that the high dB values measured in normal aquaria are unbiased. Calling activity is high at midnight and in the morning; it increases in the presence of receptive females. In a group, the dominant male calls; however, when a female becomes receptive, other males produce encounter calls.
H. Heuwinkel & G. Bunten (1996). Hydroacoustical investigations on the frog Pipa carvalhoi [abstract]. Bioacoustics 6(4): 317