I ride a shared path on my recumbent trike, I start pinging my bell about 30 mtrs before the pedestrians and carry on pinging until they turn round to look at me, I was pinging my bell once and finished doing an emergency stop when they walked further into my path, the pedestrian said " I wondered what that ringing was" I think a good blast on the "Airzound" would have had the desired effect but I didn't want to startle the pedestrian, sometimes you can't do right for doing wrong