The California carve-out for hearing protection states: "The plugs or molds shall be designed in a manner so as to not inhibit the wearer's ability to hear a si

The California carve-out for hearing protection states: "The plugs or molds shall be designed in a manner so as to not inhibit the wearer's ability to hear a siren or horn from an emergency vehicle or a horn from another motor vehicle." Ohio has a carve out specifically for motorcycles; operators of vehicles cannot (I used to own an RV where the wind and road noise at freeway speeds was well above safe levels for sustained operation).