Funding for the College’s first experimental rig totaled $126; this was considered a small sum by the standards of the time. Nevertheless, it enabled the purchase of a single device for monitoring air quality, by means of the total concentration of volatile organic compounds (VOCs) in the vicinity of the sensor. Among the VOCs that were monitored were various sulfur compounds, which have been shown to be the major contributors to the smell of farts (Suarez, Springfield, and Levitt, 1998). Note that, contrary to popular belief, the contribution of methane to fart smell is relatively minor and inconsistent across subjects. An additional virtue of our air quality sensor is that it recorded atmospheric conditions, such as pressure and temperature, which will be considered as potential predictors of fart characteristics in future posts.
Fart sounds were measured with a commercially available lapel microphone. The advantage of this device (apart from cost) was that it could be easily locked into place at a fixed distance from the experimental subject. To maintain rigorous experimental control, members of the College constructed an experimental apparatus that allowed the subject to sit comfortably upon a standard toilet seat, which was fixed to a simple wooden frame. Below the toilet seat was affixed a solid piece of PVC pipe, 12” long and 4” in diameter. The purpose of this component was to direct each fart toward the air quality sensor, which was attached to the inside of the tube, 2” from the top. The microphone was clipped to the bottom of the tube. The apparatus was dubbed the Bonaventure, for reasons that remain obscure.
Data could then be recorded relatively easily with any smartphone, by connecting the microphone to the audio input and extracting the VOC levels from the air quality sensor, via Bluetooth. On May 27, 2020 at 9:07 pm, the first fart was recorded on the Bonaventure. Below are plotted the levels of VOCs before during and after the fart; audio recording can be found below.
It was at this time that the experimental protocol was established. Each subject (most of whom were members of the College) would deposit a fart into the tube, while audio and VOC data were collected. They would remain seated for a period of no less than 2 minutes, in keeping with our air quality sensor’s sampling rate of 1 sample/minute. VOC levels were allowed to return to baseline between farts, although this requirement was not always strictly followed. As will be detailed in future posts, the College was able to record 1619 farts in this manner and to analyze the relationship between fart sound, fart smell, and various other quantities.