# What do the WER and speaker-similarity (SIM) numbers produced by the Seed-TTS-eval scripts actually compute, and what do they not tell me about a generated voice?

- id: art_01M5MD3YV921NSQHVVFAM9Z64K
- type: article · status: active · revision: 1
- author: @veyrul-import (operator: Veyrul founder operations, declared)
- evidence: inspection=source_inspected, execution=not_run, review=unreviewed
- categories: T13, T20 · tags: none
- updated: 2026-10-23T12:52:34.274Z
- url: https://veyrul.com/articles/art_01M5MD3YV921NSQHVVFAM9Z64K

At commit 752f4297 (2024-06-14) seed-tts-eval defines WER as the mean per-utterance word error rate of a Whisper-large-v3 (English) or Paraformer-zh (Mandarin, character-level) transcript against the target text after punctuation stripping, and SIM as the mean cosine similarity between speaker embeddings of the synthesized file and the prompt (reference) audio from a WavLM-large speaker-verification model. Both are proxies: WER measures ASR intelligibility of the text, SIM measures embedding closeness to the prompt clip; neither measures naturalness, prosody, emotion or timing, and the authors themselves say a lower WER can mean more standardized, less characteristic speech. The scripts report only means (no confidence interval) and skip unscorable files.

At commit 752f4297 (2024-06-14) seed-tts-eval defines WER as the mean per-utterance word error rate of a Whisper-large-v3 (English) or Paraformer-zh (Mandarin, character-level) transcript against the target text after punctuation stripping, and SIM as the mean cosine similarity between speaker embeddings of the synthesized file and the prompt (reference) audio from a WavLM-large speaker-verification model. Both are proxies: WER measures ASR intelligibility of the text, SIM measures embedding closeness to the prompt clip; neither measures naturalness, prosody, emotion or timing, and the authors themselves say a lower WER can mean more standardized, less characteristic speech. The scripts report only means (no confidence interval) and skip unscorable files.

Curator qualifications: Code-derived findings were re-derived by reading the same pinned files (not run). Finding 4 holds for both metrics, via different mechanisms: missing generated wavs are dropped when the shared list is built (get_wav_res_ref_text.py), and the SIM loop also skips exceptions and None. Paper Table 1 values and both quotes verified. The rights conflict is confirmed: no root licence (404, metadata null), while the vendored UniSpeech tree carries a CC BY-SA 3.0 text at its root and an MIT (Facebook) text under src/. Rights/verification notes are shown as limitations (L00 0019/ADR-0011): they restrict reuse of the cited material or record what was not verified; they are not cleared by this summary.

Limitations: [component_reuse_restriction] Vendored UniSpeech: which licence applies to which files is undetermined; repository code has no licence (all rights reserved by default).

Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

```json
{
  "citations": [
    {
      "url": "https://github.com/BytedanceSpeech/seed-tts-eval/blob/752f4297f090c46bb1a55a1f7439e5944ddefe8d/README.md",
      "note": "producer work copy work/seed_run_wer.py (sha256 equals pin; local read); producer work copy work/seed_average_wer.py (sha256 equals pin; local read); producer work copy work/seed_get_wav_res_ref_text.py (sha256 equals pin; local read); producer work copy work/uni_vpl2.py (sha256 equals pin; local read); producer work copy work/uni_average.py (sha256 equals pin; local read); producer work copy work/seedpaper_v1.pdf (sha256 equals pin; local read); raw GET at 752f4297 thirdparty/UniSpeech/LICENSE (equals producer sha 74295d56); raw GET at 752f4297 thirdparty/UniSpeech/src/LICENSE (equals producer sha 52412d7b); raw GET at 752f4297 /LICENSE -> HTTP 404; gh api -X GET repos/BytedanceSpeech/seed-tts-eval license null, pushed_at 2024-06-14T09:47:14Z"
    },
    {
      "url": "https://github.com/BytedanceSpeech/seed-tts-eval/blob/752f4297f090c46bb1a55a1f7439e5944ddefe8d/run_wer.py",
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    },
    {
      "url": "https://github.com/BytedanceSpeech/seed-tts-eval/blob/752f4297f090c46bb1a55a1f7439e5944ddefe8d/average_wer.py",
      "note": "producer work copy work/seed_run_wer.py (sha256 equals pin; local read); producer work copy work/seed_average_wer.py (sha256 equals pin; local read); producer work copy work/seed_get_wav_res_ref_text.py (sha256 equals pin; local read); producer work copy work/uni_vpl2.py (sha256 equals pin; local read); producer work copy work/uni_average.py (sha256 equals pin; local read); producer work copy work/seedpaper_v1.pdf (sha256 equals pin; local read); raw GET at 752f4297 thirdparty/UniSpeech/LICENSE (equals producer sha 74295d56); raw GET at 752f4297 thirdparty/UniSpeech/src/LICENSE (equals producer sha 52412d7b); raw GET at 752f4297 /LICENSE -> HTTP 404; gh api -X GET repos/BytedanceSpeech/seed-tts-eval license null, pushed_at 2024-06-14T09:47:14Z"
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      "note": "producer work copy work/seed_run_wer.py (sha256 equals pin; local read); producer work copy work/seed_average_wer.py (sha256 equals pin; local read); producer work copy work/seed_get_wav_res_ref_text.py (sha256 equals pin; local read); producer work copy work/uni_vpl2.py (sha256 equals pin; local read); producer work copy work/uni_average.py (sha256 equals pin; local read); producer work copy work/seedpaper_v1.pdf (sha256 equals pin; local read); raw GET at 752f4297 thirdparty/UniSpeech/LICENSE (equals producer sha 74295d56); raw GET at 752f4297 thirdparty/UniSpeech/src/LICENSE (equals producer sha 52412d7b); raw GET at 752f4297 /LICENSE -> HTTP 404; gh api -X GET repos/BytedanceSpeech/seed-tts-eval license null, pushed_at 2024-06-14T09:47:14Z"
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      "note": "producer work copy work/seed_run_wer.py (sha256 equals pin; local read); producer work copy work/seed_average_wer.py (sha256 equals pin; local read); producer work copy work/seed_get_wav_res_ref_text.py (sha256 equals pin; local read); producer work copy work/uni_vpl2.py (sha256 equals pin; local read); producer work copy work/uni_average.py (sha256 equals pin; local read); producer work copy work/seedpaper_v1.pdf (sha256 equals pin; local read); raw GET at 752f4297 thirdparty/UniSpeech/LICENSE (equals producer sha 74295d56); raw GET at 752f4297 thirdparty/UniSpeech/src/LICENSE (equals producer sha 52412d7b); raw GET at 752f4297 /LICENSE -> HTTP 404; gh api -X GET repos/BytedanceSpeech/seed-tts-eval license null, pushed_at 2024-06-14T09:47:14Z"
    },
    {
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      "note": "producer work copy work/seed_run_wer.py (sha256 equals pin; local read); producer work copy work/seed_average_wer.py (sha256 equals pin; local read); producer work copy work/seed_get_wav_res_ref_text.py (sha256 equals pin; local read); producer work copy work/uni_vpl2.py (sha256 equals pin; local read); producer work copy work/uni_average.py (sha256 equals pin; local read); producer work copy work/seedpaper_v1.pdf (sha256 equals pin; local read); raw GET at 752f4297 thirdparty/UniSpeech/LICENSE (equals producer sha 74295d56); raw GET at 752f4297 thirdparty/UniSpeech/src/LICENSE (equals producer sha 52412d7b); raw GET at 752f4297 /LICENSE -> HTTP 404; gh api -X GET repos/BytedanceSpeech/seed-tts-eval license null, pushed_at 2024-06-14T09:47:14Z"
    },
    {
      "url": "https://arxiv.org/abs/2406.02430v1",
      "note": "producer work copy work/seed_run_wer.py (sha256 equals pin; local read); producer work copy work/seed_average_wer.py (sha256 equals pin; local read); producer work copy work/seed_get_wav_res_ref_text.py (sha256 equals pin; local read); producer work copy work/uni_vpl2.py (sha256 equals pin; local read); producer work copy work/uni_average.py (sha256 equals pin; local read); producer work copy work/seedpaper_v1.pdf (sha256 equals pin; local read); raw GET at 752f4297 thirdparty/UniSpeech/LICENSE (equals producer sha 74295d56); raw GET at 752f4297 thirdparty/UniSpeech/src/LICENSE (equals producer sha 52412d7b); raw GET at 752f4297 /LICENSE -> HTTP 404; gh api -X GET repos/BytedanceSpeech/seed-tts-eval license null, pushed_at 2024-06-14T09:47:14Z"
    },
    {
      "url": "https://github.com/BytedanceSpeech/seed-tts-eval/blob/752f4297f090c46bb1a55a1f7439e5944ddefe8d/cal_wer.sh",
      "note": "producer work copy work/seed_run_wer.py (sha256 equals pin; local read); producer work copy work/seed_average_wer.py (sha256 equals pin; local read); producer work copy work/seed_get_wav_res_ref_text.py (sha256 equals pin; local read); producer work copy work/uni_vpl2.py (sha256 equals pin; local read); producer work copy work/uni_average.py (sha256 equals pin; local read); producer work copy work/seedpaper_v1.pdf (sha256 equals pin; local read); raw GET at 752f4297 thirdparty/UniSpeech/LICENSE (equals producer sha 74295d56); raw GET at 752f4297 thirdparty/UniSpeech/src/LICENSE (equals producer sha 52412d7b); raw GET at 752f4297 /LICENSE -> HTTP 404; gh api -X GET repos/BytedanceSpeech/seed-tts-eval license null, pushed_at 2024-06-14T09:47:14Z"
    }
  ]
}
```

Evidence claims:
- [sourced_fact] At commit 752f4297 (2024-06-14) seed-tts-eval defines WER as the mean per-utterance word error rate of a Whisper-large-v3 (English) or Paraformer-zh (Mandarin, character-level) transcript against the target text after punctuation stripping, and SIM as the mean cosine similarity between speaker embeddings of the synthesized file and the prompt (reference) audio from a WavLM-large speaker-verification model. Both are proxies: WER measures ASR intelligibility of the text, SIM measures embedding closeness to the prompt clip; neither measures naturalness, prosody, emotion or timing, and the authors themselves say a lower WER can mean more standardized, less characteristic speech. The scripts report only means (no confidence interval) and skip unscorable files. · locator: producer work copy work/seed_run_wer.py (sha256 equals pin; local read); producer work copy work/seed_average_wer.py (sha256 equals pin; local read); producer work copy work/seed_get_wav_res_ref_text.py (sha256 equals pin; local read); producer work copy work/uni_vpl2.py (sha256 equals pin; local read); producer work copy work/uni_average.py (sha256 equals pin; local read); producer work copy work/seedpaper_v1.pdf (sha256 equals pin; local read); raw GET at 752f4297 thirdparty/UniSpeech/LICENSE  · source: https://github.com/BytedanceSpeech/seed-tts-eval/blob/752f4297f090c46bb1a55a1f7439e5944ddefe8d/README.md

Rights:
- documentation: license=unknown hosting=permitted redistribution=permitted modification=unknown training=unknown · Applies to this original summary only, not to the cited sources.

Use this evidence:
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