Electronic stethoscope uses ambient noise reduction technology

The stethoscope is designed to reduce ambient noise by an average of 75% without filtering out necessary heart and lung sounds.

The Littmann Electronic Stethoscope Model 3000, recently launched by 3M Health Care, uses sensitive acoustic technology enabling clinicians to hear body sounds while other ambient noises such as human voices, medical equipment and other environmental sounds are cancelled out.

With more than 25 years of practice experience working in noisy environments such as emergency rooms, intensive-care units and a shelter, Michael Barrett, MD, said he finds a significant difference with the Littmann 3000 compared with traditional stethoscopes. Barrett is adjunct clinical associate professor of medicine and director of Cardiac Fellows Clinic at Temple University School of Medicine in Philadelphia.

“It enables me to hear heart sounds more clearly than with a traditional scope in these settings where it can be more difficult to hear important sounds,” he said.

3M said it has conducted controlled experiments and found that clinicians using the Littmann 3000 were able to pick up difficult to hear heart and lung sounds while the same sounds were missed or misidentified with acoustic, nonelectronic, cardiology stethoscopes.

Controlled experiments

In one study, 100 cardiologists listened to a prerecorded heart sound with and without a Grade I or Grade II aortic regurgitation murmur. The recordings, played in random order, were accompanied by 70 dB to 75 dB ambient noise.

Eighty-two percent of cardiologists said it was easier to detect the aortic regurgitation with the Littmann 3000 than with a traditional-design, acoustic, cardiology-type stethoscope. In that same experiment, cardiologists missed a Grade II aortic regurgitation murmur five times more often with the traditional acoustic stethoscope, the company said.

In a second experiment, 137 critical care nurses listened to, and were asked to identify, prerecorded normal and abnormal lung sounds, and 90% found it easier to detect abnormal lung sounds with the Littmann 3000.

“The ambient noise reduction technology in the Littmann 3000 allows the scope to transmit only heart sounds, not background noise or body sounds. Low frequency sounds can also be heard much louder than with traditional scopes. Because it is so much clearer, one does need to adjust to this scope and reevaluate personal descriptions of how to grade the level of a murmur,” Barrett said.

The Littmann Electronic Stethoscope Model 3000 features proprietary ambient noise technology that reduces distracting noises by an average of 75% through noise cancellation rather than filtering.

Recommends its use

Barrett said he recommends the stethoscope to other clinicians. “It will change the way they listen to their patients.”

The ambient noise technology addresses eliminating both the background noise in the air and the background noise as it travels through the patient’s body. Noise from the room enters the stethoscope through a gap in the chest piece. Once inside, the company explained, the noise meets the ambient noise that has traveled through the patient’s body and has entered the stethoscope through the diaphragm. The two pathways of noise cancel each other out, leaving only the body sounds the clinicians need to hear.

Physicians practicing in the 1970s will recall the phonocardiogram and how it helped to identify heart sounds that might not otherwise have been detected through a traditional scope, Barrett said. Phonocardiograms supplemented the traditional scope to give a more complete picture. The Littmann 3000 allows a clinician to hear sounds that previously appeared only on a phonocardiogram, he explained.

“I encourage physicians to try this scope and see for themselves how much of a difference it makes,” he said. – by Suzanne Bryla

Barrett has been a paid consultant for 3M related projects in the past.

Cardiology Today editors choose pioneering devices to highlight each month.
Selection does not imply endorsement by the editors, publisher or editorial board.