Remote Sensing of Exhaled Components Using Whistle Sounds

We propose a new remote sensing method using whistles to easily measure methane concentration in cattle breath. Recently, measurement of methane emitted by cattle is required. We attach whistles to a cattle's nose and sound is generated when the cattle exhales. We calculate molecular weight from the sound and estimate methane concentration. Whistle sounds vary depending on not only the molecular weight but the flow rate, and the effect of flow rate fluctuation on frequency was found to be up to 14.7 Hz/(L/min). When the flow rate was known, the best molecular weight resolution found to be 0.07. However, it was found that without correction for flow rate fluctuations, errors of up to 6.5 occurred in molecular weight estimation. By using two whistles in parallel, the effect of the flow fluctuation can be removed. In this way, we successfully improved the molecular weight resolution to 0.7. This is a value that can detect methane concentration fluctuations of 2.6% or more. The results indicate that the proposed method could apply to the evaluation of methane emissions from cattle.