Speaker-Segmented Audio Annotation

For one of our clients, we provided detailed annotation of audio recordings featuring multiple speakers. The task required not only accurate transcription but also precise segmentation of the audio — marking the exact start and end times of each segment, identifying individual speakers, and tagging different types of sounds (such as breaths, background noise, and unintelligible speech).

For this project, we established a workflow that allowed us to carefully process complex audio fragments and maintain consistent transcription quality — even when voices overlapped or background noise was present, with these challenges marked using special tags.

Industry:
Speech AI
Data:
20 hours of audio, 2 task types (segmentation and transcription)
Timeline:
Industry:
Speech AI
Data:
20 hours of audio, 2 task types (segmentation and transcription)
Timeline:

Challenge:

The project aimed to train models capable of automatically summarizing meetings and accurately distinguishing between different speakers. Our role was to prepare annotated audio data to power an AI bot designed to process and analyze conversations.
The client requested annotation of long audio fragments for model training, requiring precision and attention to detail at every step. Our tasks included:

  • Segmenting long audio files with exact timestamps (e.g., from 00:01:23 to 00:01:45).
  • Identifying speakers (e.g., Speaker-1, Speaker-2) and tagging unintelligible speech, breaths, and overlapping voices with dedicated labels.
  • Transcribing the text following accurate segmentation.

Project challenges included:

  • Long audio recordings (ranging from 16 to 60 minutes) with multiple speakers.
  • The need to tag specific sounds separately.
  • Strict accuracy requirements: no overlapping segments and precise time boundaries for each.

Solution:

  • 01

    Preparation and workflow organization:

    The project was split into two phases:

    • Audio segmentation by speaker and sound type.
    • Transcription of the segmented fragments.

    We assembled dedicated teams for each phase: 5 annotators for segmentation and 5 for transcription, minimizing the risk of errors.

  • 02

    Training materials provided to annotators included:

    • A detailed guideline document with tag examples.
    • Video tutorials on handling complex cases and avoiding common mistakes.
    • A Q&A table with clarifications from the client.

    We also organized feedback sessions through video reviews of each annotator’s initial work.

  • 03

    Data annotation process:

    • Annotators marked audio fragments with precise timestamps and assigned the appropriate tags.
    • A separate team then transcribed the segmented audio, using special tags (e.g., [NAME] for names) to annotate entities within the text.
  • 04

    Quality control:

    • We implemented a validation system with step-by-step checks for every file.
    • Validators documented all issues in tracking tables with examples and explanations.
    • In complex cases, a helpdesk was used for quick alignment with the client.

Results:

  • We delivered precise segmentation of 20 hours of complex audio.
    Thanks to our two-step workflow and robust validation system, we achieved high-quality annotation that met the client’s requirements.

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