Preliminary study of Acoustic Black Holes implemented in CT/MRI housings including validation experiments

An increasing number of interventional use of computer tomograph (CT) scanners and magnetic resonance tomographs (MRI) leads to the need for particularly quiet medical imaging in order to minimize the stress level for patients as well as medical staff. Due to the many different imaging sequences, noise reduction measures have to consider a wide range of different frequencies. Especially the use of Acoustic Black Holes (ABHs) seems to be a promising strategy to reduce vibration-induced noise. The objective of this study is to extend conventional measures for minimizing structural vibrations, usually realized by applying composite stiffeners, by adding ABHs directly into these stiffening components. This allows vibration maxima to be minimised efficiently. In the first step, the vibroacoustic properties of composite materials are investigated numerically and the created simulation model is validated by experiments. Based on these results, the influence of stiffeners on the structural behaviour is investigated and an optimised design for minimum surface velocities is found. To further reduce surface velocities in the frequency range where the human ear is particularly sensitive, ABHs are tested. In this context it is investigated whether ABHs can be advantageously combined with conventional stiffeners. Keywords: Medical devices, Acoustic black holes, Noise and vibration