It says: "signal processing / is about / isolating information / from noise", spread among lots of useless data about the Tshirt itself.
Why it is funny: because the message makes the point by itself. Signal processing helps separate useful data (signal) from background noise. Similarly, data science helps pointing out relevant data from non significant stuff. Actually, one might be interested in some of the noisy information on a weekly basis, when the garment starts smelling.
I apologize for not customizing the whole text (it will always be written "size XL" even for a Small).
This T-shirt is made with 100% coton, ringspun technology. It has an exceptionnaly high thickness, making it both robust and pleasant to wear. The design is manually head-transfered to the fabric via the flex technology. This T-shirt can be washed inside-out at 40°C. No tumble dryer. If you damage the printed layer by accident (or tumble dryer), iron it through a parchment paper to smooth it again.