We hear about this all the time. Does the gas motor scare fish, trolling motor, depth finder?? IMO,YES. I think it all just adds to fishing "pressure." Of course the fish are going to start to associate all of these things with traffic. And the question about fish hearing the depth finder, I can hear mind when I'm swimming around the boat. Shoot, the Lowrance transducers can even be heard out of the water!!
When catfishing, I find the hole I want to fish and then turn off the graph. But, when striper fishing, I have to leave the graph on because the school is so active you have to stay on them!! I wonder if CHIRP makes the same sound. I know that the "RP" in CHIRP stands for radar pulse so I am not sure if it is audible.