1. The Marcus Wallenberg Laboratory for Sound and Vibration Research (MWL), Department of Engineering Mechanics, KTH Royal Institute of Technology, Teknikringen 8, 114 28 Stockholm, Sweden
2. School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, UK
3. Birla Carbon, 1800 West Oak Commons Court, Marietta, GA 30062-2253, USA