The default read-only property of the SpeechSynthesisVoice interface returns a Boolean indicating whether the voice is the default voice for the current app (true), or not (false.)
The lang read-only property of the SpeechSynthesisVoice interface returns a BCP 47 language tag indicating the language of the voice.
The localService read-only property of the SpeechSynthesisVoice interface returns a Boolean indicating whether the voice is supplied by a local speech synthesizer service (true), or a remote speech synthesizer service (false.)
The name read-only property of the SpeechSynthesisVoice interface returns a human-readable name that represents the voice.
The voiceURI read-only property of the SpeechSynthesisVoice interface returns the type of URI and location of the speech synthesis service for this voice.