Relationship between airflow and frequency-based features of tracheal respiratory sound

Comparison of flow-sound relationship for different features of tracheal sound

“…One major challenge in acoustical flow estimation is that when the target flow rate changes, the flow-sound relationship changes; hence, the parameters of the linear model must change. To overcome this problem in previous studies, either flow was constant during data recording [4] or the model parameters were calibrated at different flow rates [2,6]. Since it is not always possible to capture respiratory sounds at different flow rates for calibration, in a recent study [7] the model parameters were calibrated at medium target flow rate and one of the parameters was updated automatically to compensate for the changes.…”

“…Using these features, a linear model was developed to estimate flow from tracheal sound [3,4,6,7]. One major challenge in acoustical flow estimation is that when the target flow rate changes, the flow-sound relationship changes; hence, the parameters of the linear model must change.…”

“…However, due to difficulty or inaccuracy of flow measurement techniques [1], several researchers including our group have attempted to find other methods to estimate respiratory flow [2][3][4][5][6][7].…”

“…The most commonly investigated features are sound's average power [2,3,5,6], envelope [4] and variance [7]. Using these features, a linear model was developed to estimate flow from tracheal sound [3,4,6,7].…”

“…In order to estimate airflow from sounds, several features of respiratory sounds (in particular tracheal sounds) have been investigated to find a model that best describes flow-sound relationship [2][3][4][5][6][7].…”