Feedback active noise control system and its application to MRI noise

Abstract

In this paper, a novel feedback active noise control (ANC) system combining a linear prediction filter and its application to reducing noise generated from magnetic resonance imaging (MRI) devices (MRI noise) are introduced. The proposed ANC system can reduce narrowband noise while suppressing a disturbance with broadband components. Such a disturbance makes a conventional feedback ANC system unstable or divergent because the disturbance corrupts the input signal to the system. In the proposed ANC system, a linear prediction filter is combined with the feedback ANC system to suppress the disturbance. Moreover, a modified-error feedback ANC system that can update the noise control filter using an ordinary adaptive algorithm such as NLMS instead of the Filtered-x algorithm is also incorporated with the linear prediction filter. In the modifiederror feedback ANC system, not only the stability but also the convergence rate and noise reduction ability can be improved. Simulation results demonstrate that the proposed feedback ANC systems are superior to conventional feedback ANC systems in terms of the stability, convergence rate, and noise reduction ability. Furthermore, the proposed ANC system is applied to reducing MRI noise. MRI noise consists of many sinusoidal waves whose amplitude varies with time. We found that the feedback ANC system can effectively reduce MRI noise. The proposed ANC system is implemented in a head-mounted structure to control the noise near the user's ears and to compensate for the low output of compact loudspeakers. Experimental results demonstrate that the proposed ANC system with head-mounted structure can significantly reduce MRI noise by approximately 30 dB in a high field in an actual MRI room even if the imaging mode changes frequently.

Development and Evaluation of Light-Weight Active Noise Cancellation Earphones

“…These three ANC earphones are effective over the wide frequency range from 100 Hz to 3000 Hz. As a comparison, the commercial type A headphone failed to reduce noise for frequency above In the second set of experiments, the recorded MRI noise is used as the primary noise [16]. First, we measure the MRI noise at the KEMAR's ear without placing the earphone or headphone on it.…”

“…Since the in-ear ANC earphone's error microphone is inside the ear canal and its loudspeaker has good frequency response as shown in Figure 5 (red lines), it can reduce broadband noise efficiently. In the second set of experiments, the recorded MRI noise is used as the primary noise [16]. First, we measure the MRI noise at the KEMAR's ear without placing the earphone or headphone on it.…”

Spectrogram Image Analysis of Error Signals for Minimizing Impulse Noise

“…However, as it is necessary to suppress a sudden impulse noise, an advanced ANC system, therefore, needs to have a capability to attenuate the sudden impulse noise to a certain level [5][6][7][8]. The spectrogram images give good information on how much the impulse input noise is suppressed after the application of the ANC algorithm [9][10][11][12][13][14][15].…”

Active Noise Control with Speech Enhancement Using Inverse Notch Filter

“…These noise sources have a deep impact on our daily living, and may pose problems such as noise pollution [1]. Active noise control (ANC) [2][3][4][5][6][7][8][9][10][11][12] is an effective approach to deal with noise. In this method, a signal with the same amplitude but with inverted phase is applied to noise to cancel it.…”

“…On the other hand, it has been proposed an ANC technique that just sets speakers and microphones near ear to suppress target noise of medical MRI [11,12]. In the literature [12], a linear predictor was introduced into feedback type ANC system to selectively extract periodic MRI noise from observed signals which mixes both MRI noise and disturbances. By inputting the extracted noise, ANC system was able to work steadily.…”