The Christmas Invasion - S2-E2
Corrected entry: When the Sycorax leader is talking to the humans they need to use a translation device to understand him because the TARDIS isn't translating. When they talk to the Sycorax leader he seems to have no trouble understanding their language without any apparent translation device.
Correction: Just because it isn't "apparent" doesn't mean that it isn't there. After all, the TARDIS translation circuits aren't visible either. Safe to say that, as a star-faring species, the Sycorax would have some method of understanding the races that they encounter.
Tailkinker ★