LIN: Forschungsabteilungen > Akkustik, Lernen, Sprache > Unterpunkt Ebene 3 > Unterpunkt Ebene 4
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It has long been shown that the gradient noise generated by MRI scanners (which may exceed 120 dB using Echo Planar Imaging at 3 Tesla) leads to the activation especially of primary but also of secondary auditory cortex areas. To minimize this confounding effect, we use a modified FLASH sequence which offers the possibility of slowing down the gradient switching without affecting the image quality. This reduced the noise level by > 30 dB below 500 Hz. The headphone system (Fig. 1) and a foam pillow gave > 20 dB suppression of background noise for frequencies above 0.5 kHz and more than 30 dB suppression at 2 kHz. Furthermore, the scanner room is lined with an acoustic wall to suppress reverberation (Fig. 2). All these measures add up to a “low noise” imaging protocol with a noise peak level of 48 to 54 dB SPL at the subject’s ear depending on the gradient ramp time.
Gradient noise of scanner
Here you can hear four different types of gradient noise generated by our 3 Tesla scanner using different imaging schemes.
Fig. 1: Capsules from commercially available headphones were modified by removing their magnets and integrating them into ear muffs with liquid-filled rims (Baumgart et al. 1998).
Fig. 2: Scanner room with acoustic wall to suppress reverberation.