Drivers need to see us more than we need them to hear us. As outofocus pointed out, mufflers point behind us and my biggest problem was cars shifting in to my lane. Hubby was broadsided by a driver while sitting at a red light. Threw him 3 lanes over and under an oncoming bus. That was worth a few months in hospital and physical therapy and now he mostly walks properly. He has always used glass packs rather than mufflers, so he certainly wasn’t running silent.