A method of using open-loop and adaptive control for reducing MRI noise

Recently, MRI scanner is continually used for medical diagnosis and many biomedical researches. When it operates, however, intense noise is generated. The SPL (Sound Pressure Level) of the noise approaches 130dB especially in 3T MRI. It is expected to increase because the strength of magnetic field will increase for higher-resolution image. It's a safety risk because it interferes with communication between operator and patient and could cause hearing loss to patient in extreme case. For this reason, active noise control systems have been researched for reducing low-frequency noises in which MRI noise has a high sound pressure level (SPL). The systems mainly have used feedback Filtered-X LMS (FXLMS) algorithm which is able to control only narrowband noises and possible to diverge in severe case. In this paper, we determine the property of MRI noise, and propose a method of open-loop control using ensemble average of the noise and additional adaptive control for reducing the residue which could be generated in practice.