Vibro-Acoustic Analysis of Acoustic Liners For MRI Scanners

Introduction Magnetic Resonance Imaging (MRI) scanners are popular medical diagnostic devices providing useful information about patients in a noninvasive manner. However, a disadvantage of MRI is the high level of acoustic noise generated during scanning, which is caused by the Lorentz forces acting on the gradient coils bound within an epoxy resin cylinder. As the gradient current switches direction the gradient windings vibrate, leading to the generation of sound waves [1]. Active and passive methods are commonly used for noise control. Due to the frequency limitation of Active Noise Control methods (normally effective only at relatively low frequencies), a passive noise control method using an acoustic liner was investigated by Mechefske et al. [2]. To extend their work, this paper shows some simulation results that predict the noise blocking effect of an acoustic liner, which could be used to attenuate the noise propagating into the bore of the MRI scanner (see Figure 1). Vibro-acoustic analysis was conducted to predict the acoustic performance of the liners with different thickness based on the coupling of a finite element (FE) structural model and a boundary element (BE) acoustical model.