Headphones use aviation technology to hush MRI

April 1, 2005

Aviation headphone technology adapted for use in the MR suite can cut the decibel level in half, according to a poster at the RSNA meeting.

Aviation headphone technology adapted for use in the MR suite can cut the decibel level in half, according to a poster at the RSNA meeting.

Noise levels in 3T scanners can reach up to 130 decibels, exceeding the 80 dB safety limit for chronic exposure. The din can cause permanent hearing loss in interventional radiologists, technologists, and others working in the scanner's vicinity.

Reducing noise in an MR environment is no easy task. Standard foam headsets and earplugs have a limited effect on sound attenuation. Active noise cancellation headphones, like those used in aircraft, greatly reduce decibel levels but were not compatible with an MR environment until researchers at Phone-Or in Israel adapted the technology.

The new headphones have an earpiece and a microphone that beam identical but polarized audio signals, which neutralize incoming acoustic waves from the scanner. The technology is called optoacoustical active noise control because both the microphone and earpiece work on the principle of light.

"There is no electrical signal in the magnet," said Yuvi Kahana, Ph.D., chief technology officer for Phone-Or.

The technology was tested using an MRI simulator with its maximal acoustic output set near 590 Hz. The device attenuated the fundamental resonance-acoustic noise inside the scanner-by 40 to 50 dB, with an overall resonance reduction of 20 to 30 dB. Noise reduction did not include the contribution made by the passive ear protection component of the device.