Get or set the speech volume for a synthesizer.
- macOS 10.5+
NSNumber that specifies the synthesizer’s speech volume.
Volumes are expressed in floating-point values ranging from 0.0 through 1.0. A value of 0.0 corresponds to silence, and a value of 1.0 corresponds to the maximum possible volume. Volume units lie on a scale that is linear with amplitude or voltage. A doubling of perceived loudness corresponds to a doubling of the volume.