An analysis of the energy dissipation sources acting in a vibrating aluminum plate is pre10 sented in this paper. In a first step, the contact-free modal analysis of a suspended plate 11 is conducted using a laser vibrometer and an acoustic excitation to obtain reference data. 12 The thin nylon suspension set-up guarantees a low boundary damping, which is assumed 13 to be negligible. In a second step, a number of damping sources are modeled. Acoustic 14 damping due to the noise radiation of the non-baffled plate is computed using the boundary 15 integral method and a light fluid approximation to express the vibroacoustic coupling in 16 analytical terms. The damping due to the sheared air flow along the free plate borders is 17 determined on the basis of a simple two-dimensional boundary layer model. Thermoelastic 18 damping is assessed using a Fourier series expression for the temperature field along with a 19 perturbation technique to take thermoelastic coupling into account. Since no robust model 20 is available so far to quantify viscoelastic material damping in aluminum, it is determined 21 in a last step by subtracting measured values of damping to the one that have previously 22 been computed. Aluminum viscoelastic damping turns out to be very small and almost 23 independent of frequency.