When we used to race
of West Oz coast frequently crossed paths with large whale pods and we also hoped audio noise
might steer them clear of the fleet.
I'm not sure it always worked - although a compacted race
fleet with stereos blaring and engines powered (but not turning props) - would normally scare off anything in their path.
They do sleep - and if you try to catch one you'll also appreciate how fast they can go when avoiding a boat. I'd guess at somewhere over 20 knots.
We did have one 30 foot yacht hit a sleeping whale on one noight race and the skipper
recounted it similar to the others above.
'Like hitting a brick wall'.
The whale was apparently asleep. They just saw the whales back shape awash in the wave trough ahead as they began to surf down the wave face with spinnaker
up. Far too late to take avoiding action. The whale woke with a huge thrash and rolled around in a widening pool of bloody seawater for some time. The yacht had problems of its own to sort out as with the spinnaker
up the whole rig went forward over the bow. No person on board was significantly hurt. Not sure if the whale ultimately survived or not.
They said it is clear the whale did not 'hear' them coming.