Description
Requests a volume level for the synthesized voice. Given as a number with optional decimals in the range "0.0" (silent) to 100.0 (loudest), a relative change, or values "silent", "soft", "medium", "loud" or "default"
Relative changes to values are specified as signed numbers with optional decimals, for example "+12.5". The change can be expressed as a percentage, e.g. "-10%".
VoiceXML browsers are not obligated to fully implement all speech markup tags, however, a compliant browser must silently ignore any tags it does not support, and should make its best efforts to map any unimplemented mark-up to something similar that is supported.
