dealssesame street noise canceling travel headphones…

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The volume limit is going to be dependent on what they're driven by, only a matched set, like my Sony Walkman and it's dedicated noise cancelling earbuds can generate a specific maximum SPL. Probably a lower sensitivity to reduce the SPL you get from a typical (5-10mW output) player. There's no such thing as passive noise canceling - it's "noise isolating" or "noise attenuating" by the simple fact of covering your ears.
http://en.wikipedia.org/wiki/Noise-cancelling_headphones