Evaluation of MRI compatible headphones for active noise control

Magnetic Resonance Imaging (MRI) is a powerful medical diagnostic tool. An undesirable side effect is the loud noise produced during scanning. This noise is unpleasant at best, and it may limit imaging potential. Numerous approaches have been studied in the quest to reduce patients’ noise exposure, thus allowing for improved imaging capabilities. One considered approach is to apply active noise control. This is achieved with a set of active headphones that the patient wears, which contain a pair of MRI compatible speakers to generate the control signal as well as an error microphone to monitor the target response. In order for this approach to reach fruition, any materials used in the vicinity of the MRI scanner must be made of non-ferrous materials due to the strong static magnetic field. This limits the choice of speakers and microphones, which may impede the development of the best possible active noise control system. To quantify the degree of noise reduction performance achievable with MRI-compatible hardware, two different headset/microphone combinations are evaluated. One consists of high fidelity components that are not MRI compatible, while the second utilizes piezoelectric speakers and optical microphones that are MRI compatible. Limitations and salient features of these setups that are critical to the success of applying active control are discussed.