Respiratory sound analysis offers critical and clear advantages for diagnosis and monitoring of respiratory disorders. Yet, the recording technology available today remains relatively undeveloped and non-specialized. Standard high-quality audio recording systems often do not capture the low-frequency spectrum of respiratory sounds; not to mention such equipment typically has high associated costs. Contributing to the issue is a lack of standardization of equipment used; hence, what follows is a large variability of the recordings and the inability to effectively compare results between different recording systems.

The objective of the following presented work was to design and build an electronic audio recording device along with microphone and suitable air-chamber to be placed over the trachea or lung for capturing respiratory breathing sounds. Design objectives included maintaining a cost-effective, portable, and small form-factor for the device as well as compatibility with our team’s patented obstructive sleep apnea (OSA) diagnostic algorithms to detect for the severity of OSA during either overnight sleep or wakefulness.

All desired objectives for the design were able to be realized in a compact, cost-effective, and highly accurate device. When reviewing the tracheal breathing sound recordings conducted with the device, the results identify signal content, albeit low amplitude, past 5 kHz up to 9 kHz; that indicates the previous cut-off point of many precursory studies might not have been adequate for capturing the entire characteristic features of tracheal respiratory sounds.