Guidelines for higher efficiency supported thermo-acoustic emitters based on periodically Joule heated metallic films

The paper focuses on the evaluation of the impact associated with various geometrical and material properties on the
overall acoustic performance of generic multi-layer thermo-acoustic sources. First, a generalized numerical framework
is developed using a state-of-the-art thermo-acoustic emission model for multi-layered devices and is used to
forecast the effects associated with different parameters (thickness, density, thermal conductivity, and specific heat
capacity), based on a set of 65536 simulated architectures. Then, the acoustic facility is designed, assembled, and
instrumented, and the findings of the simulation campaign are validated against experimental measurements for 32
different samples, manufactured via various vacuum deposition techniques. The results of the experimental campaign
corroborate the simulation’s prediction and indicate that the variables that have the strongest impact on the
thermo-acoustic performance are the thicknesses of the substrate and thermophone layers, as well as the backing’s
thermal conductivity. Finally, the experimental results are directly comparable with the simulation predictions and
the deviation between the two values is within the limits of the experimental accuracy, with an average deviation of
12% (maximal divergence of 28%) and best absolute performance of 0.018 [Pa/W] when measured from a distance
of 75 ½mm. Overall, the findings provide an insight into the effect of analyzed properties and offer a set of tangible
guidelines that can be applied in the future toward the design optimization process that can potentially result in
higher-efficiency thermophone-on-substrate thermo-acoustic emitters.