**Question: **What do two simultaneous farts sound like?

**Short answer:** One fart.

**Long answer:** One of the more popular applications of our research is the Fart Maker, which generates novel farts according to user-defined specifications. The number of potential farts is infinite.

The underlying algorithms are proprietary, but as part of our educational mission, we would like to help readers understand some of the basic principles. Fundamentally, the Fart Maker works by combining real farts. That is, given a series of recorded fart sounds *f _{i}(t)*, a new fart can be generated simply as:

where each *a** _{i}* defines the volume of each fart that contributes to the final output. Of course, we have developed a number of additional tricks that vastly improve the quality of

*n(t)*.

The approach works in part because combinations of farts usually sound like farts. That is, we can consider each fart of a given duration as a vector in n-dimensional space, where n is the number of audio samples in each fart. We then perform principal component analysis on our extensive fart database, yielding a set of eigenfarts, which collectively represent the different sounds present in farts. Importantly, the number of eigenfarts required to capture the vast majority of fart sounds is quite low: Even 5 eigenfarts is enough to capture 50% of the variance in a database of 2000 farts. So if we use the equation above, with the *f** _{i}* functions being eigenfarts, we can generate an infinite number of realistic farts. These sound familiar but have never been heard before by anyone.

For those readers who would like to develop an intuition of how this works, we have created a handy demo, using two eigenfarts (M = 2 in the equation). By moving the mouse around, you will vary the values of *a** _{1}* and

*a*

*, creating a new fart at each point in the space.*

_{2}CLICK anywhere to start.

DRAG to change the volume of the 2 farts. X-Axis is Fart 1, Y-Axis is Fart 2.