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Voice format: Telnyx.Ultra.<voice> Sub-100ms latency. 36 languages.
REST only — Ultra is not available over public WebSocket.

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Voice Samples

VoiceLanguageGenderSample
Telnyx.Ultra.AsherenMale
Telnyx.Ultra.CallieenFemale
Telnyx.Ultra.Claraen-USFemale

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SSML Emotions

Ultra supports inline SSML emotion tags. Place the tag before the text: 
<emotion value="excited" />Great news — your order shipped early!
Primary emotions: angry, excited, content, sad, scared. Additional: happy, enthusiastic, curious, calm, grateful, affectionate, sarcastic, surprised, confident, hesitant, apologetic, determined, frustrated, disappointed. Omitting the tag = neutral delivery. Use sparingly — Ultra interprets emotional subtext from the text itself.

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Nonverbal Cues

Insert [laughter] inline for natural laughing: 
That's hilarious! [laughter] Anyway, let me check your account.

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Language Support

Set language_boost to improve pronunciation for the target language: Arabic, Bengali, Bulgarian, Chinese, Czech, Danish, Dutch, English, Finnish, French, German, Gujarati, Hebrew, Hindi, Indonesian, Italian, Japanese, Korean, Malay, Marathi, Māori, Norwegian, Polish, Portuguese, Punjabi, Romanian, Russian, Slovak, Spanish, Swedish, Tamil, Telugu, Thai, Turkish, Ukrainian, Vietnamese.

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REST API

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Fields

FieldTypeDefaultDescription
voice_speedfloat1.0Speech rate multiplier.
language_booststring—Target language hint.
volumefloat—Output volume.
emotionstring—neutral, happy, sad, angry, fearful, disgusted, surprised.
sampling_rateinteger—Output sample rate in Hz.
output_typestringbinary_outputbinary_output, base64_output, or audio_id.

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Response

Default (binary_output): chunked audio bytes with Content-Type: audio/mpeg. With output_type: "base64_output": JSON with base64-encoded audio. With output_type: "audio_id": JSON with an audio_url for deferred retrieval.