title: Supersonic intensity and non-negative intensity for prediction of radiated sound.
abstract: Two numerical methods to identify the surface areas of a vibrating structure that radiate sound are presented. The supersonic intensity identifies only the supersonic wave components of the sound field contributing to far-field radiated sound. The supersonic intensity is calculated using a two-dimensional convolution between a spatial radiation filter and the sound field. To compute the spatial radiation filter, the shortest surface distance between two points on the structure is calculated using the geodesic distance method. The non-negative intensity is based on acoustic radiation modes and identifies the radiated sound power from a vibrating structure. Numerical models of a baffled plate, a cylinder and an engine crankcase are presented. The supersonic intensity is shown to be difficult to implement at low frequencies due to the size of the spatial radiation filter and accuracy of the surface distances. A cut-off coefficient associated with the acoustic wavenumber of the spatial radiation filter is used to reduce the aperture error. A comparison of the two intensity-based techniques both in terms of a sound power ratio and the modal assurance criterion is introduced to identify the optimal values of the cut-off coefficients that result in better convergence between the intensity techniques.
authors.affiliation: School of Mechanical and Manufacturing Engineering, UNSW, Australia, Sydney, New South Wales 2052, Australia.
authors.forename: Daipei
authors.initials: D
authors.lastname: Liu
authors.affiliation: School of Mechanical and Manufacturing Engineering, UNSW, Australia, Sydney, New South Wales 2052, Australia.
authors.forename: Herwig
authors.initials: H
authors.lastname: Peters
authors.affiliation: Vibroacoustics of Vehicles and Machines, Technische Universität München, Boltzmann Strasse 15, D-85748 Garching bei München, Germany.
authors.forename: Steffen
authors.initials: S
authors.lastname: Marburg
authors.affiliation: School of Mechanical and Manufacturing Engineering, UNSW Australia, Sydney, New South Wales 2052, Australia.
authors.forename: Nicole
authors.initials: N
authors.lastname: Kessissoglou