Ultravox is a multimodal model that can consume both speech and text as input (e.g., a text system prompt and voice user message).
The input to the model is given as a text prompt with a special <|audio|> pseudo-token, and the model processor will replace this magic token with embeddings derived from the input audio. Using the merged embeddings as input, the model will then generate output text as usual.
In the v0.7 series, the Ultravox model is trained on GLM 4.6, taking the lead on audio reasoning tasks over closed source models like gpt4o-audio, while retaining advantages in speech understanding from previous versions.
Evaluations are conducted big bench audio (audio reasoning measured in accuracy), VoiceBench (overall score averaged across multiple evaluations), as well as on covost2 (speech translation measured in BLEU), and LibriSpeech (speech recognition measured in WER).
Audio Reasoning & General Understanding
v0_7-glm-4_6 w/ reasoning
v0_7-glm-4_6 w/o reasoning
v0_6-llama-3_3-70b
v0_6-gemma-3-27b
v0_6-qwen-3-32b
gpt4o-audio
big bench audio
97.00
91.80
85.48
83.84
84.22
82.80
voicebench overall
90.75
87.05
81.81
–
–
86.75
Speech Translation & Recognition
v0_7-glm-4_6
v0_6-llama-3_3-70b
v0_6-gemma-3-27b
v0_6-qwen-3-32b
covost2 en_ar
22.89
18.92
22.68
16.91
covost2 en_ca
41.48
38.73
39.67
33.63
covost2 en_de
35.44
33.69
34.76
31.09
covost2 es_en
42.88
41.39
41.11
41.20
covost2 ru_en
50.30
43.73
49.29
47.08
covost2 zh_en
23.85
17.81
20.88
22.24
librispeech
2.28
2.55
2.73
2.88
Note that custom system prompts are used with v0_7-glm-4_6 on VoiceBench and BigBenchAudio:
BigBenchAudio in non-reasoning mode:
You are a helpful assistant. Answer the question at the end of your response.
VoiceBench in both reasoning and non-reasoning modes:
You are a helpful assistant. When answering questions: For multiple choice questions (A/B/C/D options): End your response with "The answer is [X]" where X is the letter (A, B, C, or D)