MediaTrackConstraints: volume property
Deprecated: This feature is no longer recommended. Though some browsers might still support it, it may have already been removed from the relevant web standards, may be in the process of being dropped, or may only be kept for compatibility purposes. Avoid using it, and update existing code if possible; see the compatibility table at the bottom of this page to guide your decision. Be aware that this feature may cease to work at any time.
Non-standard: This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.
  The MediaTrackConstraints dictionary's
  volume property is a ConstrainDouble
  describing the requested or mandatory constraints placed upon the value of the
  volume constrainable property.
  If needed, you can determine whether or not this constraint is supported by checking
  the value of MediaTrackSupportedConstraints.volume as returned by a call
  to MediaDevices.getSupportedConstraints(). However, typically this is
  unnecessary since browsers will ignore any constraints they're unfamiliar with.
Value
  A ConstrainDouble describing the acceptable or required value(s) for an
  audio track's volume, on a linear scale where 0.0 means silence and 1.0 is the highest
  supported volume.
  If this value is a number, the user agent will attempt to obtain media whose volume is
  as close as possible to this number given the capabilities of the hardware and the other
  constraints specified. Otherwise, the value of this ConstrainDouble will
  guide the user agent in its efforts to provide an exact match to the required volume (if
  exact is specified or both min and max are
  provided and have the same value) or to a best-possible value.
Any constraint set which only permits values outside the range 0.0 to 1.0 cannot be satisfied and will result in failure.
Examples
See the Constraint exerciser example.
Browser compatibility
BCD tables only load in the browser