Tamil AI Training Data Collection

Tamil is not a variant of a language your model already handles. The specific properties below are the ones that show up as errors in production.

• Extreme diglossia: written Tamil and spoken Tamil differ so much that read-speech corpora are near-useless for conversational ASR
• Tamil script under-specifies voicing, so க can surface as /k/, /g/, /h/ or /x/ depending on position
• Retroflex ழ (zh) is realised differently across districts and is a common transcription failure point

Tamil has 6 varieties that matter for data collection. Collecting only the standard variety produces a model that works in the capital and fails everywhere else.

• Chennai (Madras Bashai)
• Kongu (Coimbatore)
• Madurai
• Nellai (Tirunelveli)
• Kanyakumari
• Jaffna-influenced

Tanglish is the default urban register. Technology, finance, and workplace vocabulary is largely English embedded in Tamil syntax.

Specify your expected English-token ratio in the brief. It is cheaper to collect the right mix than to filter the wrong one afterwards.

Almost all public Tamil audio is literary read speech from news or scripture. Genuine colloquial Tamil, especially southern and Kongu varieties, is the single biggest gap for anyone building Tamil voice products.

This is the practical reason to commission collection rather than assemble open corpora: the gap in the public data is exactly the part your users occupy.

These are the Tamil-specific decisions that go into the style guide before any transcriber starts work.

• Transcribers normalising spoken Tamil into literary Tamil, destroying the acoustic-text alignment
• ழ / ள / ல confusion
• Inconsistent handling of English insertions: Tamil script transliteration vs Latin script must be fixed in the guide

• Colloquial spontaneous conversation transcribed verbatim
• Diglossia pairs: the same content in written and spoken register
• Command-and-control and IVR-style utterances
• District-level dialect elicitation

Recruit by district rather than by city alone; Chennai-only cohorts produce models that degrade sharply in the south and west of the state.

Tamil sessions run in Chennai, Coimbatore, Madurai, Tiruchirappalli, Salem, Tirunelveli. Multi-city fielding is the default because single-city cohorts carry an audible accent signature.

• 100% of delivered files pass automated technical QA for SNR, clipping, duration and silence
• 5-25% of files pass a second native-speaker content review, stratified by city, dialect and transcriber, and escalating to 100% on any batch that fails the agreed threshold
• Accepted yield runs 85-90% for scripted speech, 60-70% for spontaneous, 55-65% for conversational and 50-60% for telephony
• Default cohort quotas: 50/50 gender, with age bands at 30% (18-25), 40% (26-40) and 30% (41-60)
• 48 kHz / 24-bit capture, delivered as 16-bit PCM WAV, with studio sessions held below a -50 dBFS noise floor
• First response within one working day; a scoped, fixed quote within two to three

These are the figures a delivery is measured against, not aspirations. A batch that misses them is re-recorded at our cost rather than repaired.