The Simple Feedback Trainer is designed to allow sound engineering professionals simulate the process of 'ringing out' a sound reinforcement system, and help users identify howlround frequencies by ear.
I have been teaching live sound for a few years and always recommend this to my students. It is fairly accurate but innocuous so they can practice anywhere with good monitoring. A great tool! It could do with a few settings to allow the 'onset' time to be tweaked so you can replicate 'live' conditions where a mic suddenly comes on instantly.Well done to the designers nevertheless.