Active noise control of magnetic resonance imaging scanner using inverse modeling technique

In active noise control applications, internal model control (IMC) is a strategy to convert from feedback to feedforward type. In this configuration, the optimal solution of the controller is the inverse model of the secondary path. However, the inverse model of the secondary path may not always exist. In fact, for the non-minimal phase system, the inverse model is unstable. In this case, the non-causal or delayed version of the inverse model will be employed. In general, this approach is not suitable for active noise control if the objective is to treat broadband noise. However, for harmonic signal control, this is not an issue. Magnetic resonance imaging (MRI), a procedure for medical diagnosis and biomedical research, generates undesirable levels of acoustic noise emission. The noise is normally dominated by clusters of harmonics throughout the audio spectrum. Due to its tonal nature, MRI noise control is a suitable candidate for IMC. In this paper, an active noise control scheme using the inverse modeling technique is proposed and studied for prerecorded MRI noise obtained during operation of a 4T whole-body MRI scanner. The recorded MRI noise is played back through a stereo system in a sound quality room and controlled using a headset equipped with the proposed active controller. The results demonstrate that noise reduction of about 20dB is achieved.