Dataset specification · Domain scale
250 hours of Malayalam Spontaneous Speech
A domain scale build of 250 hours of Malayalam spontaneous speech. Fine-tuning a production model for a specific domain, accent range or deployment condition. Speakers talk unscripted on prompted topics — describing a process, recounting an event, arguing a position — with a moderator who prompts but does not lead.

- Volume
- 250 hours
- Scale
- Domain scale
- Per speaker
- 25–40 minutes of accepted audio per speaker
- Accepted yield
- 60–70% of recorded time is accepted
How Malayalam spontaneous speech is captured
Speakers talk unscripted on prompted topics — describing a process, recounting an event, arguing a position — with a moderator who prompts but does not lead.
A 60-minute session covering six to eight topics, recorded continuously and segmented afterwards into utterances at natural pause boundaries.
Yield at this style: 60–70% of recorded time is accepted. Long silences, moderator speech and abandoned topics are cut in post, so recorded hours run well ahead of delivered hours. Budget for the gap.
The specification
| Field | Value |
|---|---|
| Language | Malayalam (ml-IN, Malayalam) |
| Volume | 250 hours |
| Equivalent | 500 speakers at 30 minutes each, or 250 speakers at one hour each |
| Speech type | Spontaneous Speech |
| Per speaker | 25–40 minutes of accepted audio per speaker |
| File granularity | Session-length WAV plus segmented utterance files with offsets into the parent |
| Segmentation | Pause-boundary segmentation, reviewed by a native listener rather than left to VAD |
| Moderator channel | Recorded separately and excluded from the delivered speaker audio |
| Disfluency convention | Filled pauses, repetitions and false starts transcribed, not normalised away |
| Dialects | Thiruvananthapuram, Kochi (central), Malabar / Kozhikode, Thrissur |
| Transcription | Verbatim, native-speaker, second-pass reviewed |

Designing the topic bank for Malayalam
- Topic banks graded by familiarity, so speakers across education and occupation bands all have something to say
- Open prompts only — anything answerable with yes or no produces thirty seconds of audio and a stalled session
- Culturally grounded topics per region, since a prompt that works in Mumbai can draw blank looks in Guwahati
- Topic rotation across the cohort so the corpus does not over-represent a handful of subjects
- Built against Malayalam specifically: One of the most consonant-dense Indian languages; long geminates and clusters raise word error rates sharply
- Code-mixing handled explicitly rather than edited out — Manglish is standard in urban and professional speech, with heavy English noun and verb insertion.
Running a domain scale Malayalam build
Six to eight weeks. Beyond three cities the bottleneck moves from recruitment to transcription throughput, which is why the transcriber count rises faster than the engineer count.
Four to five batches on a fortnightly cadence, sequenced so the dialects you care about most land first.
Budget higher transcription effort per audio hour for Malayalam than for Hindi; speech rate and morphology make it slower to annotate.
| Parameter | At this volume |
|---|---|
| Cities | Three to four — Kochi, Thiruvananthapuram, Kozhikode, Thrissur |
| Studios | Three to four rooms plus one mobile rig |
| Recruiters | Four coordinators under one programme lead |
| Speakers | ~500–600 |
| Sessions per day | 25–30 nationally |
| Team | 1 programme lead, 4 coordinators, 8 engineers, 14 transcribers, 2 QA leads |
Cohort design
At 250 hours quotas are enforced per dialect and reconciled fortnightly. Aggregate demographics are reported per batch so drift is visible while there is still time to correct it.
Screening is for willingness to talk, not literacy, which opens the cohort to speakers a scripted protocol would exclude. Expect to over-recruit by 15% for speakers who freeze on the day.
| Dimension | Typical split | Why it matters for Malayalam |
|---|---|---|
| Gender | 50 / 50 | Pitch range differences change acoustic model behaviour; unbalanced cohorts bias recognition |
| Age | 18-25: 30%, 26-40: 40%, 41-60: 30% | Older speakers retain conservative Malayalam forms that younger urban speakers have lost |
| Region | Kerala / Lakshadweep / Puducherry (Mahe) and others | Dialect spread across 5 recognised varieties |
| Education | Mixed, including below-graduate | Prompt-reading fluency correlates with education and skews prosody |
| Condition | Studio / quiet room / field | Match the noise profile of your deployment |
Malayalam-specific considerations
- One of the most consonant-dense Indian languages; long geminates and clusters raise word error rates sharply
- Manglish is standard in urban and professional speech, with heavy English noun and verb insertion.
- Central Kerala news-reading dominates public data. Malabar and southern varieties, and fast conversational speech generally, are missing.
Quality gates for spontaneous speech
- Segment boundary review — bad boundaries produce truncated words that poison training more than they help
- Disfluency transcription consistency audited across transcribers, since conventions drift fast on this style
- Moderator speech confirmed absent from delivered segments
- Topic distribution checked per speaker so one dominant subject does not skew the language model
- Old vs new script (chillu characters, Unicode normalisation) mixed within a dataset
- Fast speech leads to dropped-word transcription errors without a second-pass QA
100% technical QA, 15% content QA with stratified sampling across city, dialect and transcriber, so no single team's output goes unchecked.
What goes wrong on spontaneous speech sessions
- Speakers who dry up after a minute, leaving sessions that look complete by duration but are mostly silence
- Drift into a reading register when a speaker becomes self-conscious about the microphone
- Moderator over-prompting, which turns a monologue corpus into an interview corpus
- Transcriber normalisation — quietly cleaning up disfluencies destroys the exact signal this style exists to capture
Risks at domain scale in Malayalam
Cost at this band is driven by: Transcription depth — verbatim with disfluencies costs materially more than clean-read transcription; Number of distinct dialect quotas rather than raw hours.
- Transcription becomes the critical path and stays there for the rest of the volume bands
- Coordinator turnover mid-build causes quota drift that is only visible in the final demographic report unless it is audited weekly
- Malayalam carries 5 recognised varieties across Kerala, Lakshadweep, Puducherry (Mahe), so the quota matrix is wider than the headline volume suggests
- Central Kerala news-reading dominates public data. Malabar and southern varieties, and fast conversational speech generally, are missing.
Deliverables
- WAV audio to your naming convention, with the per-file manifest
- Verbatim Malayalam transcripts with utterance-level timestamps
- Filled-pause and false-start markers
- Segment offsets into the parent session file
- Topic label per segment
- Speech-rate and pause-density statistics per speaker
- Per-speaker metadata: age band, gender, region, dialect, education band
- Consent records mapped to speaker IDs
- QA report with pass rates, rejection reasons and agreement statistics
- Speaker-disjoint train / dev / test splits on request
What this trains, and what it does not
- Robust ASR for real user speech
- Language modelling on natural syntax
- Disfluency detection and removal
- Prosody and speech-rate modelling
Phonetic balance cannot be guaranteed — speakers say what they say. If you need specific phone contexts or a controlled lexicon, this style has to be paired with a scripted layer.
Frequently asked
Is 250 hours of Malayalam enough?
Enough to shift word error rate meaningfully on a domain-specific deployment. For a general-purpose model in a low-resource language, still a starting layer.
Why spontaneous speech rather than another speech type?
Robust ASR for real user speech, Language modelling on natural syntax, Disfluency detection and removal are what this style is the right input for. Phonetic balance cannot be guaranteed — speakers say what they say. If you need specific phone contexts or a controlled lexicon, this style has to be paired with a scripted layer.
How long does a domain scale Malayalam build take?
Six to eight weeks. Beyond three cities the bottleneck moves from recruitment to transcription throughput, which is why the transcriber count rises faster than the engineer count. Four to five batches on a fortnightly cadence, sequenced so the dialects you care about most land first.
What does 250 hours of Malayalam spontaneous speech cost?
Quoted per delivered hour against this specification. At this band the drivers are transcription depth — verbatim with disfluencies costs materially more than clean-read transcription and number of distinct dialect quotas rather than raw hours. Send the spec and you get one fixed figure.
How much QA is applied at this volume?
100% technical QA, 15% content QA with stratified sampling across city, dialect and transcriber, so no single team's output goes unchecked.
Quote this Malayalam dataset
250 hours, spontaneous speech, Malayalam — domain scale. Adjust anything and send it.