Could MP3 Recorders Replace the Traditional Stethoscope?

The quality of sound, reproducibility for computer analysis and file-sharing potential of MP3 recordings may nudge the doctor’s stethoscope out of favour, according to Canadian researchers presenting here at the Annual Congress of the European Respiratory Society (ERS).

Determining whether the classic stethoscope could be replaced by a cheap, off-the-shelf MP3 recorder/player was the purpose of the study by Neil Skjodt, MD, MSc, Assistant Professor, Divisions of Pulmonary Medicine and Critical Care, and Bill Hodgetts, MSc, Assistant Professor, Department of Speech Pathology and Audiology, University of Alberta, Edmonton, Alberta, Canada. The team was able to record a range of respiratory sounds with different patterns by pressing its microphone directly to the chest. Different baseline breath sounds — normal (right mid-4th clavicular interspace) and then bronchial (posterior T6 spinous process), with or without added wheezing — were studied after pairwise time and short Fast Fourier Transform frequency spectrogram correlations were calculated. "The quality, clarity and purity of the loud sounds were better than I have ever heard with a stethoscope," Dr. Skjodt told the Congress.

The MP3 files were later transferred to a computer and converted into frequency curves. Computer analysis of the stored sounds showed that each had a distinct signature. The computer — like the human ear — did, however, sometimes have difficulty in processing complex or quiet breathing sounds.

Dr. Skjodt next tested respiratory specialists in training, having them identify the MP3 recordings of breath sounds. The results of this test were mixed, he noted, but promising. Wheezing noises were recognised much better than in similar historic studies, but differences in baseline breath sounds and in recognizing combinations were still not better than chance. Dr. Skjodt and Mr. Hodgetts plan to examine whether brief training in the ability to use reference recordings could improve auditory recognition. "The improved quality [of the MP3] is only one of the benefits," Dr. Skjodt emphasized, "and there would be many other advantages to using an MP3 device instead of a stethoscope."

The recorded breathing sounds can be included in the patient’s file for future reference. They can also be sent to a specialist, or processed with more sophisticated software for particularly detailed analysis. The researchers plan to continue their study, examining other clinical sounds, and assessing the impact of more highly developed audio techniques on sound recognition by the human ear. They call their device a "stethophone". The team added that further studies of custom machine recognition, correlation with human perception, Bluetooth (TM) transmission, other clinical sounds, and discrete wavelet transformations are underway.