New Stethoscope Addresses Problem of Background Noise

By April 12, 2012August 23rd, 2014General, Science and Technology
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By Catherine M. Davis

A stethoscope specially designed for use in high-noise environments such as medical evacuation vehicles is advancing toward field use.

A study is underway at Madigan Army Medical Center in Tacoma, WA, on the Noise Immune Stethoscope (NIS), developed in 2007. This study is scheduled to be completed in FY13. Scott Brady, a Biomedical Engineer at the U.S. Army Medical Materiel Agency, anticipates that within the next year, final steps will be underway to assign the NIS to the appropriate sets, kits, and outfits so the device can be used on patients in real-world operational environments.

The U.S. Army Aeromedical Research Laboratory (USAARL) developed the NIS in collaboration with Active Signal Technologies Inc., a Small Business Innovation Research partner. The NIS uses a traditional acoustic listening mode similar to that used for classic acoustic stethoscopes, but adds ultrasound-based technology that is “noise immune” to amplify heart and lung sounds. This technology allows users to switch easily from Doppler to acoustic mode.

Both modes immediately turn body sounds into electrical signals for enhanced performance. The Communications Earplug, currently used by aviators, attaches to the NIS and allows auscultation—listening to heart and lung sounds—while wearing a flight helmet.

Heart and lung sounds are a necessary component of casualty triage and ongoing care, but hearing and assessing these sounds with traditional acoustic stethoscopes is very difficult on the battlefield. It is vital that providers of military medical care providers have the necessary tools to diagnose casualties and identify the proper course of treatment. The NIS enables medical personnel to assess abnormalities of the cardiopulmonary system in high-noise environments such as within medical evacuation aircraft, on the battlefield, and in busy intensive care units.

“The dual-mode stethoscope is specifically designed for high-noise conditions,” said MAJ Tim Cho, M.D., Chief of the Aeromedical Factors Branch of USAARL’s Warfighter Health Division. “As a result, the fight surgeon or flight medic will be able to make more accurate decisions while en route to higher echelons of care during flight.”

After development of the NIS at USAARL, research began to assess the utility and durability of the new stethoscope under field conditions and in patients with cardiopulmonary pathology. In 2011, the development effort passed a number of significant milestones. The NIS received U.S. Food and Drug Administration 510(k) clearance for marketing and distribution, and received an airworthiness release for use on board the Black Hawk helicopter after rigorous laboratory and field tests by USAARL.

A 2011 USAARL research study conducted on board the USS Vinson highlighted clinicians’ ease of use of the NIS acoustic mode for identifying patients’ heart and lung sounds during high-noise operations. The study at Madigan Army Medical Center is the second one conducted by USAARL.


  • CATHERINE M. DAVIS is the Public Affairs Specialist at the USAARL, Fort Rucker, AL. She holds a B.S. in business administration with a concentration in marketing from Troy University.