Hear the Difference

You wouldn't listen to the music on your iPhone with a stethoscope connected to its speaker.... Yet, most MRI-compatible headphones offer just that; audio piped to the participant down long, acoustic tubes. The result? Awful sound quality with restricted frequency response and restricted utility in research.

Hear for yourself in our 48 second demo:

BOLDfonic includes everything you need for high-quality audio delivery in the MR:

• A pair of electro-dynamic headphones. Various options are available to suit different types and sizes of headcoils.
• A set of earphones to accommodate even the the tightest of headcoils
• Fully–loaded amplifier system which provides all the controls you need for rigorous multimodal EEG/fMRI studies. Supports multiple signal sources and can drive two sets of headphones in parallel.
• AudioFile USB sound processor with automated synchronous triggering capabilities
• Desktop microphone for communication from the technologist. Ask us about our optional bi-directional communication feature which use the noise-cancelling Optoacoustics FORM-III participant microphone. Compact monitor speakers are included too, so you can always hear the same audio as your participant.

Better Audio Quality

BOLDfonic headphones utilize moving-coil transducers positioned in the headphone body, just like hi-fi headphones! As you can see illustrated in Figure 1, this results in excellent frequency response across a wide dynamic range.

Figure 1. Frequency response of BOLDfonic system headphones compared with standard acoustic audio system.

Though standard moving-coil transducers utilizing a magnet aren't safe in an MRI room, the BOLDfonic headphone system features a unique electro-dynamic driver that utilizes the magnetic field of the MRI scanner to drive the headphone membrane. An additional piezoelectric driver can be fitted to some headphones, which enables them to be used outside the bore as well.

Reduced Gradient Noise

When compared to a standard scanner audio system, the circumaural, closed-back BOLDfonic headphones offer improved acoustic isolation from the gradient-noise of the MRI scanner. Acoustic attenuation is increased by at least 15dB over most of the audible range, as illustrated in Figure 2.

Where space permits, soft memory foam cushions can also be inserted between the head and contact points of the coil to provide even better isolation, reduce bone conduction and improve participant comfort.

Figure 2. Attenuation characteristics of BOLDfonic system headphones compared with standard acoustic audio system.

Easy to install

BOLDfonic headphones connect through the RF penetration panel using a pair of BNC bulkhead connectors. Two independent stereo channels maintain the high channel separation of the amplifiers. The filter/transformer set blocks DC levels, separates the ground of the RF cage from the ground of the audio system, and reduces unwanted RF-signals by about 85dB. Extra filters inside the scanner room reduce RF signals even further by about 90dB.

Figure 3. BOLDfonic system installation schematic.