Monopole mobility is a measurement of how much a guitar top will move under the oscillatory forces of the strings. More movement = more sound. It’s not the sole arbiter of a good guitar, but it’s a good indicator; the instrument also has to play in tune, be even in volume across the strings and frets, and have an alluring tone. But anyone who tells you that the guitars they build are responsive, sensitive, “powerful” etc. should be able to substantiate their claims. I can, using this measure. My guitars, both classical and steel string, have significantly higher monopole mobility than the average of the comparison guitars, and the comparison guitars included the best guitars I could get my hands on. This doesn’t translate to double the volume (however you choose to measure that!) but it translates to what you hear being very noticeably louder than the average.