Two species of the Australian genusTympanophora, Tympanophoranew species 1 (T.n.sp.l)andT. similisshare the same habitat and are sympatric with several other bushcricket species. Males ofT. similiscall in aggregations, whilst males ofT.n.sp.lfrequently sing closer to heterospecific than to conspecific neighbours. Hence males ofT.n.sp.lmay have to cope with more severe problems of interspecific acoustic interference than males ofT. similis.Laboratory experiments support field data which indicate that the number of callingT.n.sp.lmales decreases when the number of singing males ofT. similisincreases. Acoustic interactions between the two species and sympatric bushcricket species occur in the laboratory. Heterospecific song affects chirp interval and/or chirp pattern in the twoTympanophoraspecies. Males ofT.n.sp.lrespond to the song of the sibling speciesT. similisdifferently than to the calls of the more distantly related tettigoniids tested. However, the response ofT. similismales appears to depend on the temporal structure of the heterospecific songs. The results do not suggest that the frequency content of the heterospecific calls is important for the song interference which has been observed inTympanophora.