Dataset specification · Domain scale
250 hours of Marathi Spontaneous Speech
A domain scale build of 250 hours of Marathi 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 Marathi 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 | Marathi (mr-IN, Devanagari) |
| 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 | Standard (Puneri), Varhadi (Vidarbha), Marathwadi, Konkani-influenced coastal Marathi |
| Transcription | Verbatim, native-speaker, second-pass reviewed |

Designing the topic bank for Marathi
- 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 Marathi specifically: Retains the retroflex lateral ळ, which has no Hindi or English equivalent and is frequently substituted with ल by non-native transcribers
- Code-mixing handled explicitly rather than edited out — Mumbai and Pune speech mixes Marathi, Hindi, and English in the same sentence. Marathi-only recordings collected in Pune under-represent the Mumbai reality of tri-lingual switching.
Running a domain scale Marathi 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.
A representative Marathi cohort should be split roughly 40% western Maharashtra, 25% Vidarbha, 20% Marathwada, 15% Konkan rather than concentrated in Pune.
| Parameter | At this volume |
|---|---|
| Cities | Three to four — Mumbai, Pune, Nagpur, Nashik |
| 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 Marathi |
|---|---|---|
| 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 Marathi forms that younger urban speakers have lost |
| Region | Maharashtra / Goa / parts of Karnataka and others | Dialect spread across 6 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 |
Marathi-specific considerations
- Retains the retroflex lateral ळ, which has no Hindi or English equivalent and is frequently substituted with ल by non-native transcribers
- Mumbai and Pune speech mixes Marathi, Hindi, and English in the same sentence. Marathi-only recordings collected in Pune under-represent the Mumbai reality of tri-lingual switching.
- Available Marathi speech data is dominated by standard Puneri read speech. Vidarbha, Marathwada, and coastal Konkan varieties are severely under-collected, which is exactly where deployed voice products lose accuracy.
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
- ळ vs ल substitution by Hindi-trained transcribers
- Anusvara placement varies between conservative and modern orthography
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 Marathi
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
- Marathi carries 6 recognised varieties across Maharashtra, Goa, parts of Karnataka, so the quota matrix is wider than the headline volume suggests
- Available Marathi speech data is dominated by standard Puneri read speech. Vidarbha, Marathwada, and coastal Konkan varieties are severely under-collected, which is exactly where deployed voice products lose accuracy.
Deliverables
- WAV audio to your naming convention, with the per-file manifest
- Verbatim Devanagari 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 Marathi 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 Marathi 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 Marathi 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 Marathi dataset
250 hours, spontaneous speech, Marathi — domain scale. Adjust anything and send it.