Innovative Noise-Immune Stethoscope

A new type of stethoscope enables doctors to hear the sounds of the body in extremely loud situations, such as during the transportation of wounded soldiers in helicopters.

The new ultrasound-based stethoscope transmits a sound signal at 2.3 megahertz into the patient's body. This sound is reflected back to the stethoscope at a slightly different frequency because of the velocity of the internal organs. The difference in frequencies between the sound wave that is transmitted and the sound wave that is received--a result of the Doppler effect--can be computed to determine the motion of the internal organs. This difference in frequency is then converted into audible sound. The new stethoscope is nearly impervious to loud noise and is capable of making accurate readings at noise levels up to 120 decibels.

Because they are based on different physical principles than conventional stethoscopes, ultrasound stethoscopes produce a markedly different sound. Whereas an acoustic stethoscope yields a lub-dub sound from a heartbeat, with the first beat being the strongest, an ultrasound stethoscope will yield a ta-da-ta pattern, with the second beat being the strongest.

The new stethoscope was developed by Active Signal Technologies (Linthicum Heights, MD. USA) in collaboration with the U.S. Army Aeromedical Research Laboratory (USAARL, Fort Rucker, AL, USA), and was presented at the fourth joint meeting of the Acoustical Society of America and the Acoustical Society of Japan, held in November-December 2006 in Honolulu (Hawaii, USA).

"Having heard so much about the first critical hour that may mean life or death for a seriously injured person, I feel fortunate to have been in a position to lead a great team of dedicated researchers in enabling medical auscultation in very noisy environments,” said USAARL stethoscope project team leader Adrian Houtsma. "I expect this invention to save many lives that otherwise might have been lost.”



Related Links:
U.S. Army Aeromedical Research Laboratory