I have a ACR, Fox40 Micro and Sharx...the Sharx sounds a bit louder and has a lower pitch than the Micro(I covered my ears). The Sharx is slightly easier to blow, but its about twice as thick. Both fox's can be submerged and blown immediately, as the water clears. The ACR is about 1/3 the thickness of the sharx, and is loud, with 2 distinct pitches. Both fox's are louder. The ACR is easiest to blow. The ACR does not clear well. It takes quite a bit of air to clear and has a bit of water in it that makes the pitch higher. It has to be shaken to get rid of the water.