Investigation of microphone placement on assessment of restricted pulsatile flow

This study seeks to assess the severity of a restriction through acoustic measurements, inspired by aortic stenosis. Combining the acoustic power spectrum, the bispectrum, and associated bicoherence exposes different characteristics in the obtained signals. This study investigates the influence of measurement location together with the severity of restrictions to create an understanding of these correlating factors. Varying blockages are created with 3D printed semi-triangular valve models, inspired by the tricuspid shape of a heart valve, spanning from completely open to 82 percent restricted. Initial findings show that the distribution of energy over frequencies below 300 Hz are indicative of the restriction present, regardless of the microphone placement or the Reynolds number of the flow. Previous investigations have found the amount of restriction to be inversely proportional to the bicoherence of the acoustic signal. Current analysis shows that the level of coherence between frequencies decreases with increasing restriction percentage, consistent with prior studies. Using a combination of these three measures, a predictive model for non-invasively assessing the severity of the restriction is sought.