While this metronome has a few appealing features, well, what use is a metronome if you cant hear it? Without exaggeration, Ill say that Ive got a wall clock in my house that ticks louder than this metronome. Youd be better off with Metronome+ or Tempo - both perfectly audible.
JPWGibson about Beat On - Advanced Metronome with Training Modes, v1.2.1