Man alive, don't get the managers working with audio. "Doubling the stream" might work if you're using a signed audio format rather than an unsigned one, and the format is in the same endianness as the host computer uses. Neither of which are guaranteed when working with audio.

But of course, the ear perceives loudness in a logarithmic way (the decibel scale), so for it to be perceived as "twice as loud", it generally needs an exponential increase. Very high and low frequencies need more, since we're less sensitive to them and don't perceive increases so well.