Audio modelActive
Gemini 3.8 Flash TTS
- Released
- September 22, 2026
- Data date
- October 7, 2026
- Model class
- Access
Gemini 3.8 Flash TTS is Google's speech model for nuanced delivery, regional dialects, and long-form multi-turn output.
Google positions Gemini 3.8 Flash-Lite TTS for high-throughput production and real-time voice agents, while Flash TTS focuses more on voice fidelity and expression.
Specifications and access
| Specification | Value and source |
|---|---|
| Model class | Text-to-speech modelSource |
| Access | Gemini APISource |
| Input modalities | TextSource |
| Output modalities | AudioSource |
| API model ID | gemini-3.8-flash-ttsSource |
| Focus | Studio-grade voice fidelity, nuanced acting, regional dialects, and stability across long-form multi-turn outputSource |
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Measurements without matching peer values
These measurements have no matching peer values under the same test conditions. Their original values and sources remain available here.
Hume Real World VoiceEQ: Young-adult voice accuracy (Show measurement, test conditions, and source)
- Source value
- 34
- Score
- 34
- Metric
- accuracy for the young-adult voice-control attribute
- Unit
- %
- Benchmark version
- Report card dated 2026-09-24
- Category
- audio
- Direction
- Higher is better
- Source type
- independent-evaluator
- Evaluator
- Hume Real World VoiceEQ report card
- Status
- active
- Retrieved at
- 2026-10-07
- Methodology
- Independent evaluation. Three human raters screened by Hume; blinded evaluation with randomized clip order on held-out prompts. Gemini 3.8 Flash TTS; point estimate for the specific young-adult voice-control attribute.
- Context
- Hume publishes no per-question sample counts, confidence intervals, or model configurations. It documents three screened human raters, blinded scoring, randomized order, and held-out prompts. Hume discloses a non-exclusive licensing agreement with Google.
Hume Real World VoiceEQ: Volume-control pass rate (Show measurement, test conditions, and source)
- Source value
- 56.9
- Score
- 56.9
- Metric
- pass rate for the volume-control instruction
- Unit
- %
- Benchmark version
- Report card dated 2026-09-24
- Category
- audio
- Direction
- Higher is better
- Source type
- independent-evaluator
- Evaluator
- Hume Real World VoiceEQ report card
- Status
- active
- Retrieved at
- 2026-10-07
- Methodology
- Independent evaluation. Three human raters screened by Hume; blinded evaluation with randomized clip order on held-out prompts. Gemini 3.8 Flash TTS; point estimate for the volume-control instruction.
- Context
- Hume publishes no per-question sample counts, confidence intervals, or model configurations. It documents three screened human raters, blinded scoring, randomized order, and held-out prompts. Hume discloses a non-exclusive licensing agreement with Google.
Artificial Analysis Provider Voice Arena Elo (Show measurement, test conditions, and source)
- Source value
- 1275
- Score
- 1275
- Metric
- human blind-pairwise voice preference Elo
- Unit
- elo
- Benchmark version
- September 2026 snapshot
- Category
- audio
- Direction
- Higher is better
- Sample
- 2446
- Confidence interval
- 16
- Lower confidence bound
- 1259
- Upper confidence bound
- 1291
- Source type
- independent-evaluator
- Evaluator
- Artificial Analysis Provider Voice Arena
- Status
- active
- Retrieved at
- 2026-10-07
- Methodology
- Independent evaluation. Blind pairwise evaluation used each provider's native voice set; 2,446 model appearances across eight voices. Higher Elo means more frequent preference. September 2026 snapshot.
- Context
- Appearances are not a count of unique people or prompts. The snapshot does not give a per-model evaluation date range.
Hume Real World VoiceEQ: Extended long-form stability (Show measurement, test conditions, and source)
- Source value
- 2.89
- Score
- 2.89
- Metric
- five-point stability rating
- Unit
- rating
- Benchmark version
- Report card dated 2026-09-24
- Category
- audio
- Direction
- Higher is better
- Source type
- independent-evaluator
- Evaluator
- Hume Real World VoiceEQ report card
- Status
- active
- Retrieved at
- 2026-10-07
- Methodology
- Independent evaluation. Three human raters screened by Hume; blinded evaluation with randomized clip order on held-out prompts. Gemini 3.8 Flash TTS; long-form stability dimension.
- Context
- Hume publishes no per-question sample counts, confidence intervals, or model configurations. It documents three screened human raters, blinded scoring, randomized order, and held-out prompts. Hume discloses a non-exclusive licensing agreement with Google.
Hume Real World VoiceEQ: Expressivity–Reliability Frontier Score (Show measurement, test conditions, and source)
- Source value
- 0.92
- Score
- 0.92
- Metric
- TOPSIS composite on a 0–1 scale
- Unit
- ratio
- Benchmark version
- Report card dated 2026-09-24
- Category
- audio
- Direction
- Higher is better
- Source type
- independent-evaluator
- Evaluator
- Hume Real World VoiceEQ report card
- Status
- active
- Retrieved at
- 2026-10-07
- Methodology
- Independent evaluation. Three human raters screened by Hume; blinded evaluation with randomized clip order on held-out prompts. Gemini 3.8 Flash TTS; TOPSIS closeness to the ideal (1, 1) corner across expressivity and reliability questions.
- Context
- Hume publishes no per-question sample counts, confidence intervals, or model configurations. It documents three screened human raters, blinded scoring, randomized order, and held-out prompts. Hume discloses a non-exclusive licensing agreement with Google.
Hume Real World VoiceEQ: Same-speaker similarity (Show measurement, test conditions, and source)
- Source value
- 3.53
- Score
- 3.53
- Metric
- same-speaker similarity rating out of five
- Unit
- rating
- Benchmark version
- Report card dated 2026-09-24
- Category
- audio
- Direction
- Higher is better
- Source type
- independent-evaluator
- Evaluator
- Hume Real World VoiceEQ report card
- Status
- active
- Retrieved at
- 2026-10-07
- Methodology
- Independent evaluation. Three human raters screened by Hume; blinded evaluation with randomized clip order on held-out prompts. Gemini 3.8 Flash TTS; voice replication same-speaker dimension; report card ranks this model 11th of 13.
- Context
- Hume publishes no per-question sample counts, confidence intervals, or model configurations. It documents three screened human raters, blinded scoring, randomized order, and held-out prompts. Hume discloses a non-exclusive licensing agreement with Google.
Hume Real World VoiceEQ: Acting / Role-fit (Show measurement, test conditions, and source)
- Source value
- 3.69
- Score
- 3.69
- Metric
- five-point human-rater score
- Unit
- rating
- Benchmark version
- Hume Real World VoiceEQ report card, 2026-09-24
- Category
- audio
- Direction
- Higher is better
- Source type
- independent-evaluator
- Evaluator
- Hume Real World VoiceEQ report card
- Status
- active
- Retrieved at
- 2026-10-07
- Methodology
- Independent evaluation. Gemini 3.8 Flash TTS preview; Hume Real World VoiceEQ blind evaluation with randomized clips, three screened human raters, and held-out prompts; Acting / Role-fit dimension, reported cohort of 34 models.
- Context
- Hume publishes no per-dimension clip counts or confidence intervals. It documents three screened human raters, blinded scoring, randomized clip order, and held-out prompts. Hume discloses a non-exclusive licensing agreement with Google.
Hume Real World VoiceEQ: Expressiveness (Show measurement, test conditions, and source)
- Source value
- 3.46
- Score
- 3.46
- Metric
- five-point human-rater score
- Unit
- rating
- Benchmark version
- Hume Real World VoiceEQ report card, 2026-09-24
- Category
- audio
- Direction
- Higher is better
- Source type
- independent-evaluator
- Evaluator
- Hume Real World VoiceEQ report card
- Status
- active
- Retrieved at
- 2026-10-07
- Methodology
- Independent evaluation. Gemini 3.8 Flash TTS preview; Hume Real World VoiceEQ blind evaluation with randomized clips, three screened human raters, and held-out prompts; Expressiveness among instruction-capable models dimension, reported cohort of 8 models.
- Context
- Hume publishes no per-dimension clip counts or confidence intervals. It documents three screened human raters, blinded scoring, randomized clip order, and held-out prompts. Hume discloses a non-exclusive licensing agreement with Google.
Hume Real World VoiceEQ: Voice identity (Show measurement, test conditions, and source)
- Source value
- 4.53
- Score
- 4.53
- Metric
- five-point human-rater score
- Unit
- rating
- Benchmark version
- Hume Real World VoiceEQ report card, 2026-09-24
- Category
- audio
- Direction
- Higher is better
- Source type
- independent-evaluator
- Evaluator
- Hume Real World VoiceEQ report card
- Status
- active
- Retrieved at
- 2026-10-07
- Methodology
- Independent evaluation. Gemini 3.8 Flash TTS preview; Hume Real World VoiceEQ blind evaluation with randomized clips, three screened human raters, and held-out prompts; Voice identity among instruction-capable models dimension, reported cohort of 8 models.
- Context
- Hume publishes no per-dimension clip counts or confidence intervals. It documents three screened human raters, blinded scoring, randomized clip order, and held-out prompts. Hume discloses a non-exclusive licensing agreement with Google.
Hume Real World VoiceEQ: Language stability (Show measurement, test conditions, and source)
- Source value
- 3.21
- Score
- 3.21
- Metric
- five-point human-rater score
- Unit
- rating
- Benchmark version
- Hume Real World VoiceEQ report card, 2026-09-24
- Category
- audio
- Direction
- Higher is better
- Source type
- independent-evaluator
- Evaluator
- Hume Real World VoiceEQ report card
- Status
- active
- Retrieved at
- 2026-10-07
- Methodology
- Independent evaluation. Gemini 3.8 Flash TTS preview; Hume Real World VoiceEQ blind evaluation with randomized clips, three screened human raters, and held-out prompts; Language stability dimension, reported cohort of 34 models.
- Context
- Hume publishes no per-dimension clip counts or confidence intervals. It documents three screened human raters, blinded scoring, randomized clip order, and held-out prompts. Hume discloses a non-exclusive licensing agreement with Google.
Hume Real World VoiceEQ: Reliability (Show measurement, test conditions, and source)
- Source value
- 3.64
- Score
- 3.64
- Metric
- five-point human-rater score
- Unit
- rating
- Benchmark version
- Hume Real World VoiceEQ report card, 2026-09-24
- Category
- audio
- Direction
- Higher is better
- Source type
- independent-evaluator
- Evaluator
- Hume Real World VoiceEQ report card
- Status
- active
- Retrieved at
- 2026-10-07
- Methodology
- Independent evaluation. Gemini 3.8 Flash TTS preview; Hume Real World VoiceEQ blind evaluation with randomized clips, three screened human raters, and held-out prompts; Reliability dimension, reported cohort of 34 models.
- Context
- Hume publishes no per-dimension clip counts or confidence intervals. It documents three screened human raters, blinded scoring, randomized clip order, and held-out prompts. Hume discloses a non-exclusive licensing agreement with Google.
Hume Real World VoiceEQ: Long-form speaker stability (Show measurement, test conditions, and source)
- Source value
- 3.42
- Score
- 3.42
- Metric
- five-point human-rater score
- Unit
- rating
- Benchmark version
- Hume Real World VoiceEQ report card, 2026-09-24
- Category
- audio
- Direction
- Higher is better
- Source type
- independent-evaluator
- Evaluator
- Hume Real World VoiceEQ report card
- Status
- active
- Retrieved at
- 2026-10-07
- Methodology
- Independent evaluation. Gemini 3.8 Flash TTS preview; Hume Real World VoiceEQ blind evaluation with randomized clips, three screened human raters, and held-out prompts; Long-form speaker stability dimension, reported cohort of 34 models.
- Context
- Hume publishes no per-dimension clip counts or confidence intervals. It documents three screened human raters, blinded scoring, randomized clip order, and held-out prompts. Hume discloses a non-exclusive licensing agreement with Google.
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Sources and data date
| Type | Evidence and data date |
|---|---|
| Research status | Research date October 7, 2026. 4 source URLs checked. This documents the inspected sources, not an exhaustive inventory of every publication. |
| Not published | hume-sample-counts-and-intervals Original wording Hume publishes no per-model clip or rating counts and no confidence intervals for the cited VoiceEQ metrics. |
| Not found in the inspected sources | objective-speech-error-metrics Original wording The sources checked contain no transcript-based WER/CER test for the generated TTS audio; available results measure voice quality, stability, and preference. |
| Additional source | Google Gemini API release notes (retrieved October 7, 2026) · Google Gemini API release notes · Editorial description reviewed October 7, 2026 |
| Additional source | Google Gemini text-to-speech documentation (retrieved October 7, 2026) · Google Gemini text-to-speech documentation · Editorial description reviewed October 7, 2026 |
| Additional source | Gemini 3.8 Flash TTS model documentation (retrieved October 7, 2026) |
| Additional source | Artificial Analysis Provider Voice Arena (retrieved October 7, 2026) |
| Additional source | Hume Real World VoiceEQ report card (retrieved October 7, 2026) |