Confirmed, sound definatly cuts in and out randomly, sometimes goes to full volume when volume is actually turned off. It may be conflicting with other notifications, e.g. More than once I have sound turned low (one bar), I receive an email ping noise, and ACR switches to full volume. When I check my volume settings, they are still on one bar though. Using volume button doesn't change in game volume, but when moving to a different menu sound (usually) resets to iPad setting.
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To add to this, if your iPad is in silent mode (sound toggle either via the side or the app switch menu), some events can bring the sound back, like ending a game (victory or defeat screen) or transitioning between sections (like from main menu to versus and/or back). This can only be avoided if the actual volume is turned to zero AS WELL AS putting the device in silent mode. Which is annoying.