AI Speech Data Collection

Training data that makes voice AI understand

End-to-end speech data collection and annotation — from recruiting consented native speakers to delivering production-ready ASR, TTS, and voice AI datasets across 40+ languages.

Trusted by AI teams worldwide

50M+

Annotations delivered

98.5%

Average QA accuracy

40+

Languages supported

2K+

Domain expert annotators

48h

Pilot batch turnaround

Use cases

Speech data for every
voice AI application

Whether you’re training an ASR engine, fine-tuning a TTS system,

or building a multilingual voice assistant, Synnth sources and

labels the exact data your model needs.

Automatic Speech Recognition (ASR)

Diverse, accurately transcribed speech corpora covering accents, speaking styles, noise conditions, and domain-specific vocabulary for ASR model training and benchmarking.

Verbatim transcription, Noise conditions, Accent coverage, Domain vocab

Text-to-Speech (TTS) Synthesis

Studio-quality and naturalistic recordings from professional and diverse voice talents for neural TTS model training, including expressive, conversational, and multi-style datasets.

Phonetically balanced, Prosody-rich, Multi-style, SSML-aligned

Voice Assistants & Conversational AI

Spontaneous, task-oriented dialogue recordings in real-world acoustic environments — covering a full range of intents, domains, and speaker demographics for voice assistant training.

Intent labeling, Slot tagging, Dialogue acts, Far-field

Wake Word & Keyword Spotting

Targeted keyword and wake phrase recordings across speaker ages, genders, accents, and noise conditions — with carefully designed negative samples to reduce false activations.

Positive samples, Negative samples, Device conditions, Demographics

Call Centre & Telephony AI

Realistic telephone-quality speech data spanning customer service domains, accented English, and code-switching scenarios for contact centre automation and sentiment analysis models.

8kHz telephony, Sentiment tags, Code-switching, Speaker diarization

Speaker Verification & Biometrics

Longitudinal multi-session recordings from diverse speaker pools, with session variability controls and demographic stratification for speaker ID, verification, and anti-spoofing research.

Multi-session, Stratified demographics, Anti-spoofing, Channel variation

What we collect & annotate

Every type of speech data,
fully covered

From raw audio sourcing to richly labeled, production-ready datasets

— Synnth manages the complete speech data pipeline.

Data collection

Native-speaker recruitment - consented participants matched to your demographic targets.
Scripted read speech - phonetically balanced prompts read by diverse voice talents.
Spontaneous conversational speech - naturalistic, unscripted dialogue scenarios.
Wake word & command capture - targeted keyword recordings across environments.
Telephony & far-field sessions - device-specific recording setups replicating deployment conditions.
Multilingual & dialect sourcing - regional varieties and low-resource language specialists.
Noise & acoustic augmentation - controlled SNR environments, reverberant rooms.

Annotation & labeling

Verbatim transcription - word-for-word accuracy with disfluency marking conventions.
Speaker diarization - multi-speaker segmentation and identity tagging.
Phoneme-level labeling - fine-grained forced-alignment and manual correction.
Sentiment & emotion tagging - valence, arousal, discrete emotion categories.
Language & accent identification - ISO 639 language codes, dialect classification.
Intent & entity annotation - NLU-ready slot and intent labeling for voice AI.
Prosody & paralinguistics - pitch, rate, emphasis, and non-verbal sound tags.

How it works

From scope to production-ready dataset
in four steps

A transparent, repeatable pipeline designed for ML teams who need reliable data fast — with quality gates at every stage.

Define scope

Share your use case, target languages, speaker demographics, acoustic conditions, and annotation schema. We produce a detailed specification with your ML team — including ontologies and quality rubrics.

Recruit & record

We recruit consented native speakers matched to your demographic quotas, run recording sessions in calibrated acoustic environments, and validate audio quality before annotation begins.

Annotate & QA

Domain-specialist annotators label your audio. Every item passes inter-annotator agreement scoring, automated acoustic QA, and senior reviewer sign-off before leaving our pipeline.

Deliver & iterate

Receive clean datasets in your preferred format (WAV + JSON, FLAC + CSV, ELAN, TextGrid, etc.) with a full QA report. Free revisions within scope; ongoing batches on your schedule.

Why Synnth

Built for teams that can't afford bad data

Six things that separate Synnth from generic transcription services and data labeling platforms.

Human-in-the-loop QA

Every automated label is reviewed and validated by expert humans. We never outsource quality to algorithms alone — speech is too nuanced for fully automated pipelines.

99.2% QA pass rate

Native-speaker annotators

Transcriptionists and annotators are native speakers of the target language, not crowd workers using machine translation. Dialect knowledge is built in.

40+ languages

Domain expertise matched

Medical, legal, financial, and technical speech requires specialist annotators. We match your project to domain experts — not generalists who approximate terminology.

200+ domain specialists

Enterprise-grade security

All audio encrypted at rest and in transit. GDPR compliant, HIPAA-ready, NDAs on every engagement. Your proprietary recordings never leave our controlled environment.

Fast pilot SLAs

Pilot batches of up to 10,000 utterances can be delivered in 48–72 hours. So you can validate data quality before committing to full-scale production volumes.

48h pilot delivery

Custom annotation schemas

We build task-specific ontologies, labeling guidelines, and quality rubrics tailored to your model’s exact requirements — not off-the-shelf templates that don’t fit your edge cases.

AI teams trust Synnth for production-grade training data

From raw data collection to fully annotated datasets — start with a free pilot, no commitment, no setup fees.

FAQ

Common questions about AI speech data collection

Everything you need to know before starting a speech data project with Synnth.

💡 Can’t find your answer here? Talk to our team — we typically respond within one business day.

What is AI speech data collection?

AI speech data collection is the process of recording, sourcing, and curating spoken audio specifically to train machine learning models such as automatic speech recognition (ASR), text-to-speech (TTS), voice assistants, wake word detectors, and speaker verification systems. High-quality, diverse, and accurately labeled speech data is the foundation of accurate, robust voice AI.

How does Synnth recruit speakers for speech data collection?

We maintain a network of consented, compensated speakers segmented by language, dialect, age, gender, and profession. For each project we define demographic quotas with your team, recruit speakers who meet those criteria, and obtain written consent for the intended data use. All participants are informed about how their recordings will be used.

What formats are speech datasets delivered in?

Datasets are delivered in your preferred format. Audio files are typically WAV (16-bit PCM, 16kHz or 44.1kHz) or FLAC, paired with transcription and metadata files in JSON, CSV, XML, TextGrid (Praat), or ELAN. We can align to custom schemas or pipeline formats your ML infrastructure already uses.

How is speech annotation quality ensured?

Our QA pipeline combines multiple layers: (1) initial audio quality checks for clipping, noise floor, and recording artifacts; (2) transcription by trained native-speaker annotators; (3) inter-annotator agreement measurement on a statistically significant sample; (4) automated consistency validation; and (5) senior reviewer sign-off. We maintain a standard 98.5% QA accuracy and share a full QA report with every delivery.

Can Synnth collect speech data in noisy or specific acoustic environments?

Yes. We can source or simulate specific acoustic conditions including office noise, traffic, cafeteria environments, far-field room acoustics, and telephony codec degradation. For device-specific projects (smart speakers, in-car systems, earbuds) we can configure recording setups to match your deployment hardware.

What is the minimum project size and turnaround time?

We offer pilot batches starting from 1,000 utterances, typically delivered within 48–72 hours. For ongoing or high-volume projects, we work with your team to establish recurring SLAs with dedicated project managers and priority queue access.

How is our proprietary audio data kept secure?

All audio is uploaded through encrypted channels (TLS 1.3), stored at rest with AES-256 encryption, and processed only within access-controlled annotation environments. We sign NDAs on every engagement and can operate under strict data handling agreements for regulated industries including healthcare and financial services.

Does Synnth support code-switching and multilingual speech datasets?

Yes. We have extensive experience with code-switching datasets where speakers move between two or more languages mid-utterance — a common real-world pattern in regions like South Asia, Southeast Asia, and the Middle East. We can recruit bilingual speakers and provide language-segment-level labels alongside full transcriptions.

How is pricing structured for speech data collection projects?

Pricing depends on language, annotation task complexity, speaker demographic requirements, volume, and turnaround time. We offer per-utterance and per-audio-hour pricing for standard tasks, and custom quotes for complex or regulated projects. Contact us for a free, no-commitment estimate. Pilot batches for qualifying projects may be offered at no charge.

Get started

Start your speech data project today

Tell us your use case, languages, and volume targets. Our team will respond within one business day with a scoping plan and a no-obligation quote.