Comparison of mechanical vibration and acoustic noise in the open-air MRI

Abstract

The paper analyzes and compares spectral properties of an acoustic noise produced by mechanical vibration of the gradient coils during scanning in the open-air magnetic resonance imager (MRI) working in a weak magnetic field. Selection of a usable type of the vibration sensor and the noise pickup microphone for measurement in weak magnetic field conditions is also discussed. The changes in acoustic noise spectral properties caused by loading of the holder of the lower gradient coils by the weight of the examined person lying in the scanning area of the MRI device is analyzed, too. The achieved results will be first of all used to design a correction filter for noise suppression in the speech signal recorded simultaneously with 3D human vocal tract scanning. Finally, the paper describes measurement and determination of the time delay between the resulting noise signal and the vibration impulses originated in the gradient coils. The obtained results will serve for description of the influence of the vibration on the acoustic noise and the way it travels through the plastic holder in the MRI device scanning area.