The locations at which pinging was detected shown in the map in post 9647 are around 26 km apart. Wikipedia states
A 37.5 kHz (160.5 dB re 1 μPa) pinger can be detectable 1–2 kilometres (0.62–1.24 mi) from the surface in normal conditions and 4–5 kilometres (2.5–3.1 mi) in good conditions. A 37.5 kHz (180 dB re 1 μPa) transponder pinger can be detected 4–5 kilometres (2.5–3.1 mi) in normal conditions and 6–7 kilometres (3.7–4.3 mi) in good conditions
There have been numerous posts about convergence,ducting etc that could result in longer ranges and, I presume, that is how these pings are being detected so far apart. However it shows what a big area of uncertainty there must still be about the location of the pingers. I seem to recall that when the first announcements of hearing the pingers were made at the press conference a few days ago, Angus Houston said they were searching a 3 mile square area to narrow down the source - it now looks quite a bit bigger than that.