Maybe useful - Everyday Looper is an iOS app for recording short looping samples, up to four at a time. That is, you record a sound and it plays it from start to finish over and over in a loop, and you can record another sound up to the same length and play them next to each other, or adjust the volume on them individually.

It's intended for musical use, but might do for what you ask. It is not free, so you might check it out on Youtube to see how it works and why it might be good for quick record-hear-compare feedback.

(iOS / iPhone does have a basic sound recorder in it, as you may know).