Assembly: Microsoft.Xna.Framework (in microsoft.xna.framework.dll)
Volume adjustment is based on a decibel, not multiplicative, scale. For example, when the device volume is half of maximum (about 7 in the Zune user interface), setting Volume to 0.6f or less is silent or nearly so, not volume 4 as you would expect from a multiplicative adjustment.
Setting Volume to 0.0 subtracts 96 dB from the volume. Setting Volume to 1.0 subtracts 0 dB from the volume. Values in between 0.0f and 1.0f subtract dB from the volume proportionally.