num volume

Source 

@DomName('SpeechSynthesisUtterance.volume')
@DocsEditable()
num get volume =>
    _blink.BlinkSpeechSynthesisUtterance.instance.volume_Getter_(this);
void volume=(num value)

Source 

@DomName('SpeechSynthesisUtterance.volume')
@DocsEditable()
set volume(num value) =>
    _blink.BlinkSpeechSynthesisUtterance.instance.volume_Setter_(this, value);