Electrodynamic headphones and woofers for application in magnetic resonance imaging scanners

Abstract

Electrodynamic speakers compatible with (functional) magnetic resonance imaging (MRI) are described. The speakers magnets are removed, their function is replaced by the scanner's magnetic field, resulting in an uncommon but efficient operation. The method can be used with headphones as well as woofers. Functional MRI is not associated with any known biological risks, but as a method for visualization of task-specific activation of brain regions it is undesirably noisy. Thus, it requires both noise protection and efficient sound transmission systems for delivering acoustic stimuli to subjects. Woofers could possibly be used in active noise-control systems. The speakers described in this paper can be used for either task.

Tinnitus- and Task-Related Differences in Resting-State Networks

“…MR-compatible electrodynamic headphones (MR Confon GmbH, Magdeburg, Germany; (Baumgart et al 1998)) were used during the fixed-state runs to deliver sound stimuli from a standard PC with soundcard to participants. Subjects were asked to wear foam earplugs underneath the headset to further diminish the acoustic noise created by the scanner.…”

Neurotologic and Functional MRI Findings in a Patient With Bilateral Profound Deafness Having Brown–Vialetto–Van Leare Syndrome

“…The rationale to use monofrequent tones at the given frequency was to produce a consistent stimulus at a maximum suprathreshold level that could be provided by the sound system of ''MR confon GmbH'' (Magdeburg, Germany; http://www.mr-confon.de/en/products.html). The earphones used in the present study are exactly the same as described in Baumgart et al (5). In their analysis, these earphones were extensively tested and measured concerning sound pressure level (SPL) (5).…”

“…The earphones used in the present study are exactly the same as described in Baumgart et al (5). In their analysis, these earphones were extensively tested and measured concerning sound pressure level (SPL) (5). The earphones used in the present study are suited for noise protection because they are built with an active noise-suppression design without hindering the efficient transmission of sound (5).…”

An active free-field equalizer for headphones used in functional magnetic resonance imaging

“…This method is mainly used for speech communication, as the achievable frequency-range is limited. Modified electrodynamic headphones which use the existing magnetic field of the MRI scanner (Baumgart et al [7]) or electrostatic headphones are alternatives which provide better sound-quality (e.g. Palmer et al [8]).…”