Noise Reduction and Audio Output System for fMRI

描述（由申请人提供）：我们建议开发一种先进的降噪和音频刺激呈现系统，用于功能性磁共振成像（fMRI）的听力研究。功能磁共振成像被广泛用于在受试者积极执行任务或接受感官刺激时产生大脑活动图像。在听觉刺激下获取功能磁共振成像大脑图像的过程尤其困难，因为功能磁共振成像设备产生的噪音非常强烈，其水平高达130 dB SPL，因此会严重干扰预期的声刺激。此外，FMRI设备使用的强磁场排除了许多音频设备中常用的材料，因此不可能使用传统的耳机来呈现声音。此外，商业上可用的系统，虽然设计充分提供声刺激，但只提供适度的环境噪声衰减。

DESCRIPTION (provided by applicant): We propose to develop an advanced noise reduction and audio stimulus presentation system for use during studies of hearing employing functional Magnetic Resonance Imaging (fMRI). fMRI is being used extensively to produce images of brain activity while a subject actively performs a task or receives sensory stimulation. The process of acquiring fMRI brain images in response to auditory stimulation is especially difficult because the noise generated by fMRI equipment is extremely intense, with levels up to 130 dB SPL, and so interferes significantly with the intended acoustic stimuli. In addition, FMRI apparatus employs an intense magnetic field that excludes the use of many materials commonly used in audio devices so that it is impossible to use conventional earphones for sound presentation. In addition, commercially available systems, while designed to present acoustic stimuli adequately, provide only modest attenuation of ambient noise. The goal of the proposed system is to provide maximum possible attenuation of ambient sound while providing audio signals of research quality. The methods to be used to achieve these goals include the combination of three attenuation techniques: (1) a circumaural muff, (2) insert earplugs, and (3) active noise reduction (ANR) within the muff. ANR is an effective complement to an earplug and a muff because it provides highest attenuation at low frequencies, while plugs and muffs attenuate better at higher frequencies. A small electrostatic transducer coupled to a sound channel in the earplug will deliver stimuli. Another, larger electrostatic transducer in the muff will be used in conjunction with a small microphone and circuitry to form an ANR system. In Phase I a complete prototype system will be constructed for assessment of feasibility, attenuation, audio quality, and compatibility with the fMRI magnetic field. Device attenuation will be measured using subject threshold shifts. The system will be refined and further developed into a manufacturable prototype in Phase II.