That sounds like the phone app may not have quite the sensitivity needed to get an accurate read. Also worth noting is while less noise is objectively always better for hunting, the pitch and sound quality of the noise your bow makes is oftentimes more influential on game animals than the presence of noise. Animals hear sudden noises all the time such as acorns dropping, thunder crashing, limbs falling, squirrels hopping around, etc. Having a bow that sounds like a natural sound, such as a deep pitched "thud" that sounds like a fat acorn hitting soft ground, results in far less string jumping/alerting than bows which sound out of place, such as a high pitched THWACK of the string on a limb followed by a WHOOSH of the string followed by the PING-TEEEEEEWWWAAANNNNGGG tuning fork noise of a badly vibrating string combined with a little wrist slap POP.