{
  "benchmark": "LiveLingo Phone-Line Bandwidth Test 2026",
  "published": "2026-08-18",
  "license": "CC-BY-4.0",
  "page_url": "https://www.livelingo.io/guides/phone-call-translation-accuracy",
  "method_url": "https://www.livelingo.io/research/phone-line-bandwidth-method",
  "audio": {
    "wideband": "audio-wideband.zip",
    "phone_line": "audio-phoneline.zip",
    "chain": "16kHz -> 8kHz resample (anti-alias) -> G.711 mu-law -> decode -> 16kHz container"
  },
  "quality_by_system": {
    "LiveLingo": {
      "wideband": 4.269,
      "narrowband": 4.348,
      "delta": 0.079,
      "pct_drop": 1.9,
      "ci95": [
        0.012,
        0.144
      ],
      "n": 160
    },
    "Azure Speech Translation": {
      "wideband": 3.542,
      "narrowband": 3.5,
      "delta": -0.042,
      "pct_drop": -1.2,
      "ci95": [
        -0.15,
        0.065
      ],
      "n": 160
    },
    "Whisper + GPT-4o-mini": {
      "wideband": 3.337,
      "narrowband": 3.333,
      "delta": -0.004,
      "pct_drop": -0.1,
      "ci95": [
        -0.063,
        0.054
      ],
      "n": 160
    },
    "Google (STT v2 + Translate v3)": {
      "wideband": 3.913,
      "narrowband": 3.885,
      "delta": -0.027,
      "pct_drop": -0.7,
      "ci95": [
        -0.081,
        0.025
      ],
      "n": 160
    }
  },
  "by_pair": [
    {
      "pair": "ar->fr",
      "n": 20,
      "LiveLingo": {
        "wideband": 4.317,
        "narrowband": 4.283,
        "delta": -0.033
      },
      "Azure Speech Translation": {
        "wideband": 3.133,
        "narrowband": 3.417,
        "delta": 0.283
      },
      "Whisper + GPT-4o-mini": {
        "wideband": 2.433,
        "narrowband": 2.433,
        "delta": -0.0
      },
      "Google (STT v2 + Translate v3)": {
        "wideband": 4.017,
        "narrowband": 4.017,
        "delta": 0.0
      }
    },
    {
      "pair": "id->ko",
      "n": 20,
      "LiveLingo": {
        "wideband": 4.1,
        "narrowband": 4.217,
        "delta": 0.117
      },
      "Azure Speech Translation": {
        "wideband": 3.1,
        "narrowband": 3.067,
        "delta": -0.033
      },
      "Whisper + GPT-4o-mini": {
        "wideband": 3.567,
        "narrowband": 3.717,
        "delta": 0.15
      },
      "Google (STT v2 + Translate v3)": {
        "wideband": 3.833,
        "narrowband": 3.733,
        "delta": -0.1
      }
    },
    {
      "pair": "ms->zh",
      "n": 20,
      "LiveLingo": {
        "wideband": 4.383,
        "narrowband": 4.533,
        "delta": 0.15
      },
      "Azure Speech Translation": {
        "wideband": 3.083,
        "narrowband": 3.1,
        "delta": 0.017
      },
      "Whisper + GPT-4o-mini": {
        "wideband": 2.917,
        "narrowband": 2.883,
        "delta": -0.033
      },
      "Google (STT v2 + Translate v3)": {
        "wideband": 3.317,
        "narrowband": 3.133,
        "delta": -0.183
      }
    },
    {
      "pair": "pl->de",
      "n": 20,
      "LiveLingo": {
        "wideband": 3.9,
        "narrowband": 3.9,
        "delta": -0.0
      },
      "Azure Speech Translation": {
        "wideband": 3.183,
        "narrowband": 3.017,
        "delta": -0.167
      },
      "Whisper + GPT-4o-mini": {
        "wideband": 3.233,
        "narrowband": 3.3,
        "delta": 0.067
      },
      "Google (STT v2 + Translate v3)": {
        "wideband": 3.45,
        "narrowband": 3.45,
        "delta": 0.0
      }
    },
    {
      "pair": "pt->de",
      "n": 20,
      "LiveLingo": {
        "wideband": 4.517,
        "narrowband": 4.5,
        "delta": -0.017
      },
      "Azure Speech Translation": {
        "wideband": 4.283,
        "narrowband": 4.033,
        "delta": -0.25
      },
      "Whisper + GPT-4o-mini": {
        "wideband": 3.9,
        "narrowband": 3.717,
        "delta": -0.183
      },
      "Google (STT v2 + Translate v3)": {
        "wideband": 4.417,
        "narrowband": 4.417,
        "delta": 0.0
      }
    },
    {
      "pair": "tr->de",
      "n": 20,
      "LiveLingo": {
        "wideband": 3.85,
        "narrowband": 4.217,
        "delta": 0.367
      },
      "Azure Speech Translation": {
        "wideband": 3.767,
        "narrowband": 3.8,
        "delta": 0.033
      },
      "Whisper + GPT-4o-mini": {
        "wideband": 3.817,
        "narrowband": 3.767,
        "delta": -0.05
      },
      "Google (STT v2 + Translate v3)": {
        "wideband": 3.983,
        "narrowband": 4.033,
        "delta": 0.05
      }
    },
    {
      "pair": "vi->ja",
      "n": 20,
      "LiveLingo": {
        "wideband": 4.5,
        "narrowband": 4.467,
        "delta": -0.033
      },
      "Azure Speech Translation": {
        "wideband": 3.8,
        "narrowband": 3.483,
        "delta": -0.317
      },
      "Whisper + GPT-4o-mini": {
        "wideband": 2.533,
        "narrowband": 2.5,
        "delta": -0.033
      },
      "Google (STT v2 + Translate v3)": {
        "wideband": 4.4,
        "narrowband": 4.383,
        "delta": -0.017
      }
    },
    {
      "pair": "zh->vi",
      "n": 20,
      "LiveLingo": {
        "wideband": 4.583,
        "narrowband": 4.667,
        "delta": 0.083
      },
      "Azure Speech Translation": {
        "wideband": 3.983,
        "narrowband": 4.083,
        "delta": 0.1
      },
      "Whisper + GPT-4o-mini": {
        "wideband": 4.3,
        "narrowband": 4.35,
        "delta": 0.05
      },
      "Google (STT v2 + Translate v3)": {
        "wideband": 3.883,
        "narrowband": 3.917,
        "delta": 0.033
      }
    }
  ],
  "source_transcript_drift": {
    "Whisper": {
      "raw": 5.7,
      "clean": 1.99,
      "identical_pct": 80.7,
      "n": 280
    },
    "Google": {
      "raw": 0.44,
      "clean": 0.44,
      "identical_pct": 96.4,
      "n": 280
    }
  }
}