Update: The 'mud whisperer' guy from the Portland dredge conference was actually right
I thought his whole thing about listening to the pump sounds to guess sediment density was just showboating. But last Tuesday on the Columbia River, our flow meter broke and I tried his trick, calling out '40% sand, 60% silt' just from the hum. The lab sample came back 38/62. Has anyone else tried this or am I just getting lucky?