Butadiene copolymers are brominated using certain quaternary ammonium tribromides as the brominating agent in a first step, and then with elemental bromine in a second bromination step. First and second sawdust collecting members respectively have first and second intake ports which are respectively disposed above and under the table in the vicinity of the blade so as to collect sawdust scattering around the blade and falling through a hole in the table. The invention also concerns a headphone comprising one or two such listening devices.