On the Origin of Cardiovascular Sounds Recorded From the Ear

Area of Science:

• Biomedical Engineering
• Physiological Monitoring
• Acoustics

Background:

• Conjectures exist regarding the origin of ear-recorded sounds: heart sounds or local vascular activity.
• Previous studies have not definitively verified these hypotheses.
• Understanding signals from body-coupled microphones in the ear requires further investigation.

Purpose of the Study:

• To investigate the origin of sounds captured by body-coupled microphones placed in the ear.
• To differentiate between cardiac and vascular sources of these ear-recorded signals.
• To enhance understanding of physiological signals measured using in-ear microphones.

Main Methods:

• 10 subjects underwent various postures and exercise with in-ear body-coupled microphones.
• Synchronized data collection included electrocardiography, photoplethysmography, and respiration.
• Signal analysis involved time-locking body-coupled microphone and photoplethysmography data to the electrocardiography R-peak.

Main Results:

• Body-coupled microphone signals were significantly time-locked to the electrocardiography R-peak.
• No significant differences were observed between signals recorded from the left and right ears.
• Analysis indicated signals reflect arterial pressure waves near the microphone.

Conclusions:

• Signals recorded by in-ear body-coupled microphones primarily reflect arterial blood pressure waves.
• This finding helps clarify the physiological basis of sounds detected by ear-worn devices.
• The study provides evidence against solely cardiac origin for these signals.