Jul 17

What is speaker diarization?

Speaker diarization has become an increasingly mature and robust technology in recent years, thanks to advancements in machine learning, deep learning, and signal processing techniques. This blog post explores some basic aspects of speaker diarization: from concept to its application, as well as its benefits and use cases.

What is speaker diarization?

Speaker diarization involves the task of distinguishing and segregating individual speakers within an audio stream. This allows for the separation of each speaker's utterances in the transcript generated by automatic speech recognition (ASR) technology. This means that the speakers are distinguished based on their distinctive audio characteristics, and their individual utterances are grouped together into separate buckets. This characteristic is sometimes referred to as speaker labels or speaker change detection. Customers who work with audio containing multiple speakers and want transcripts in a more readable format often employ speaker diarization.

a woman talking to her smartphone using voice assistant

Speaker diarization is a combination of speaker segmentation and speaker clustering. Speaker segmentation helps find speaker change points in an audio stream, while speaker clustering group together speech segments based on speaker characteristics.

How does speaker diarization work?

Speaker diarization often involves four main subtasks:

  1. Detection: Identify segments within the audio that comprise speech, distinguishing them from periods of silence or noise.
  2. Segmentation: Separate the detected regions into smaller audio sections.
  3. Representation: Employ a distinctive vector to display those segments.
  4. Attribution: Assign a speaker label to each segment based on its distinctive representation.

Diarization systems may incorporate additional subtasks. In a comprehensive end-to-end AI diarization system, some of these subtasks can be combined to enhance productivity. Let's delve deeper into the purpose and functionality of these subtasks in the context of speaker diarization.

StageZero audio annotation segmentation tool

The initial step, detection, is often carried out using a Voice Activity Detection (VAD) model. This model determines whether a particular audio region contains voice activity, encompassing various vocal elements such as speech. Deepgram takes advantage of ASR (Automatic Speech Recognition) transcripts, which provide precise word timings at the millisecond level, enabling accurate identification of regions containing speech.

Segmentation typically involves uniformly dividing and separating the audio using small windows of a few hundred milliseconds or somewhat longer sliding windows. The use of small windows ensures that each segment predominantly contains the speech of a single speaker. However, smaller segments yield less informative representations, making it challenging to determine the speaker from very brief clips. To address this, instead of relying solely on fixed windowing, we utilize a neural model that identifies speaker changes to generate segments.

Representing each segment involves embedding it, often employing neural models trained to differentiate between various speakers. Statistical representations like i-vectors have been largely surpassed by embeddings such as d-vectors or x-vectors.

Attribution, a critical aspect, is approached through various methodologies, making it an active area of research. Significant approaches include Spectral and Agglomerative Hierarchical Clustering algorithms, Variational Bayes inference algorithms, and diverse trained neural architectures.

These subtasks collectively contribute to the overall functionality of the diarization system, enabling robust and effective identification of speakers in audio recordings.

What are the benefits of speaker diarization?

Speaker diarization serves the purpose of enhancing transcript legibility and gaining a deeper comprehension of a conversation's context. By distinguishing individual speakers, it aids in extracting crucial points or action items from the dialogue, attributing statements to their respective speakers, and determining the number of speakers involved.

Its applications are diverse, such as in reviewing post-call sales meetings where the need arises to ascertain whether the customer agreed to the business terms or if it was merely the salesperson's claim.

Additionally, it facilitates identifying the individual responsible for the final buying decision. In real-time educational settings, caption diarization becomes invaluable as it enables online students to better discern who uttered specific statements during classroom interactions - providing clarity on whether it was the professor or a fellow student contributing to the discussion.

Use cases

Conversational AI

Speaker diarization plays a crucial role in conversational AI by enabling systems to understand and analyze multi-party conversations. Here are some ways speaker diarization is utilized in conversational AI:

  • Speech recognition and transcription: Speaker diarization helps in accurately transcribing and attributing speech to individual speakers in a conversation. By separating the speech of different speakers, it improves the quality and readability of the transcriptions, making them more useful for further analysis and processing.
  • Speaker identification: Speaker diarization allows conversational AI systems to identify and differentiate between speakers involved in a conversation. This information is valuable for various applications, such as personalized responses or directing specific actions to the appropriate speaker.
  • Sentiment analysis and emotion detection: By associating speech segments with individual speakers, speaker diarization aids in analyzing the sentiment and emotional state of each participant in a conversation. This information can be used to tailor responses or gauge the overall sentiment dynamics within the dialogue.
  • Dialogue management: Speaker diarization helps in managing multi-turn conversations by keeping track of each speaker's contributions. It enables conversational AI systems to maintain context, handle interruptions, and generate coherent and contextually relevant responses.
  • Voice assistant personalization: Speaker diarization allows voice assistants to recognize different users within a household or shared environment. This recognition enables personalized experiences, such as retrieving individualized preferences, accessing personal information, or providing tailored recommendations based on specific user profiles.
  • Conversational analytics: By accurately identifying speakers and attributing their contributions, speaker diarization enables in-depth analysis of conversations. It provides insights into turn-taking patterns, speaker interactions, conversational dynamics, and other metrics that can be used for improving conversational AI systems, customer service, or extracting valuable business intelligence.

Read more: The ultimate guide to implementing Conversational AI in your business

Audio management

Speaker separated transcripts or captions enable more convenient searches for company or product attribution and enhance comprehension of viewers or listeners' contributions. Some examples of speaker diarization use cases in audio management:

  • Content indexing and search: Speaker diarization enables the indexing and categorization of audio content based on individual speakers. By automatically segmenting audio recordings into speaker-specific segments, it becomes easier to search and retrieve specific sections of audio based on speaker identity. This is particularly useful in large audio archives or databases where quick access to specific speakers or their contributions is required.
  • Transcription services: Speaker diarization enhances transcription services by accurately associating transcribed text with the corresponding speakers. It helps in producing more readable and coherent transcripts, making it easier to understand who said what in the audio recording. This is valuable for various applications such as meeting minutes, interview transcriptions, or legal proceedings.
data transcription network icon
  • Content analysis and insights: Speaker diarization facilitates content analysis by separating speakers' contributions within audio recordings. It enables the extraction of speaker-specific insights, patterns, or sentiment analysis from the audio content. This can be useful in market research, media analysis, customer feedback analysis, or other scenarios where understanding individual speakers' perspectives is crucial.
  • Audio editing and post-production: In audio production workflows, speaker diarization assists in streamlining editing and post-production processes. It allows for easier manipulation and adjustment of audio segments specific to individual speakers, such as removing or enhancing specific parts, adjusting volume levels, or applying effects selectively.
  • Voice biometrics and speaker verification: Speaker diarization is employed in voice biometrics and speaker verification systems. By accurately separating speaker segments, it enables the creation of speaker models or templates used for speaker identification, verification, or authentication purposes. This is utilized in applications such as voice-controlled access systems, forensic voice analysis, or speaker recognition in telecommunications.

Read more: Beginner’s guide to audio annotation and Annotation tools – market overview 

Speaker analysis

Speaker diarization is a fundamental technique used in speaker analysis, allowing for the identification and characterization of individual speakers within audio recordings. Here are some techniques speaker diarization is used in speaker analysis:

  • Speaker identification: Speaker diarization aids in identifying individual speakers within an audio recording or dataset. By segmenting the audio and assigning speaker labels to each segment, it enables the determination of the identity of speakers. This is valuable in various applications, such as forensic investigations, voice biometrics, or determining the authorship of anonymous recordings.
  • Speaker verification and authentication: Speaker diarization supports speaker verification and authentication systems. By separating the voices of different speakers, it facilitates the comparison of speaker characteristics with stored voice profiles or reference samples to confirm the claimed identity of a speaker. This is applied in voice-controlled access systems, security applications, or forensic voice analysis.
  • Speaker characteristics analysis: Speaker diarization assists in analyzing various speaker characteristics and vocal attributes. By segmenting the audio based on speaker changes, it allows for the extraction and examination of features such as pitch, intonation, voice quality, speaking style, accent, or emotional expression specific to each speaker. This aids in studying speaker traits, language patterns, or sociolinguistic aspects.
  • Speaker diagnostics and voice disorders: Speaker diarization is utilized in diagnosing and studying voice disorders. By differentiating speaker segments, it enables the analysis of vocal characteristics, speech patterns, or abnormalities associated with specific speakers. This supports the assessment, monitoring, and treatment of voice disorders in fields such as speech pathology or otolaryngology.
  • Speaker profiling and forensic analysis: Speaker diarization assists in building speaker profiles for forensic analysis. By separating the voices of speakers involved in a conversation or recording, it helps in profiling speakers based on their speech patterns, vocal characteristics, or linguistic traits. This aids in forensic voice comparison, speaker profiling, or providing expert testimony in legal cases.
  • Sociolinguistics and dialectology: Speaker diarization contributes to sociolinguistic and dialectological studies. By segmenting audio recordings based on speaker changes, it allows for the analysis of speech variations, dialects, or sociolinguistic patterns specific to different speakers. This provides insights into regional accents, language variation, or sociolinguistic phenomena in language research.

Read more: What is speech analytics? 


Speaker diarization plays a crucial role in compliance-related activities by helping organizations effectively manage and analyze audio data for regulatory and legal requirements. Here are some ways speaker diarization is used in compliance:

  • Call monitoring and quality assurance: Speaker diarization allows compliance teams to monitor and analyze recorded calls to ensure adherence to regulatory guidelines and quality standards. By separating speakers and identifying participants, it becomes easier to review specific interactions, identify compliance breaches, and provide feedback or training to employees.
  • Compliance reporting and auditing: Speaker diarization aids in generating accurate compliance reports by attributing specific statements or actions to individual speakers. Compliance officers can review transcribed and segmented conversations to verify regulatory compliance, identify potential violations, and maintain comprehensive audit trails for regulatory purposes.
  • Regulatory investigations and legal discovery: During regulatory investigations or legal proceedings, speaker diarization helps in analyzing audio evidence. It allows for efficient identification and extraction of relevant segments from audio recordings, ensuring that specific statements or actions can be attributed to the appropriate individuals. This assists in building cases, responding to regulatory inquiries, and facilitating legal discovery processes.
  • Data privacy and information security: Speaker diarization assists in managing data privacy and information security requirements. By accurately identifying speakers, compliance teams can ensure that sensitive information is handled appropriately, access to confidential conversations is controlled, and privacy obligations are fulfilled in accordance with applicable regulations.
  • Compliance training and education: Speaker diarization can be utilized in compliance training programs to provide real-life examples and scenarios. By using segmented audio recordings with identified speakers, training sessions can focus on specific interactions, highlighting compliance best practices or illustrating potential compliance risks and challenges.

Read more: Investigation: How data privacy impacts enterprises and individuals and StageZero's guide and checklist to privacy and AI


Speaker diarization plays a significant role in the legal field, providing valuable assistance in various aspects of legal proceedings. Below are some examples of how speaker diarization is used in law:

  • Court transcripts and legal documentation: Speaker diarization is employed to create accurate transcripts of court proceedings, depositions, or legal interviews. By separating speakers and attributing their statements, it helps in producing clear and organized documentation of the proceedings, making it easier for lawyers, judges, and other legal professionals to review and reference specific parts of the conversation.
  • Evidence analysis and review: In legal investigations or litigation, speaker diarization aids in analyzing audio or video evidence. It helps identify individual speakers, distinguish their contributions, and determine the context and sequence of statements made during the recorded interactions. This assists in building a comprehensive understanding of the evidence, evaluating witness testimonies, and preparing legal arguments.
  • Deposition and witness examination: Speaker diarization facilitates the analysis and preparation of depositions and witness examinations. It allows lawyers to review previous testimonies, identify key statements, and establish the credibility or consistency of witnesses' statements based on their past contributions. This helps in cross-examinations, presenting evidence, and strengthening legal strategies.
  • Legal discovery and case review: Speaker diarization assists in the review and analysis of large volumes of audio or video data during legal discovery. By organizing and indexing the content based on speakers, it enables efficient search, retrieval, and analysis of specific interactions or statements relevant to the case. This helps lawyers in identifying critical evidence, understanding case dynamics, and preparing legal arguments.
  • Forensic analysis and voice identification: Speaker diarization is used in forensic voice analysis and voice identification. It helps in identifying individual speakers within recorded evidence, comparing voice samples, and determining the consistency or similarity of voices across different recordings. This is valuable for establishing the identity of speakers, addressing voice-related disputes, or providing expert testimony in voice-related legal matters.


Speaker diarization has several applications in the realm of sales, aiding in various aspects of sales processes and customer interactions:

  • Sales call analysis: Speaker diarization is employed to analyze sales calls or meetings. It helps in segmenting the conversation into distinct speaker segments, allowing sales teams to review and evaluate specific interactions between salespeople and prospects or clients. By identifying individual speakers, sales managers can assess communication effectiveness, identify areas for improvement, and provide targeted coaching and feedback.
  • Training and onboarding: Speaker diarization can be utilized in sales training and onboarding programs. By separating the voice of trainers or sales experts from trainees or new hires, it enables focused analysis and feedback. This helps in evaluating trainee progress, identifying areas of improvement, and providing targeted guidance for skill development.
  • Customer insights and relationship management: Speaker diarization aids in extracting valuable insights from customer interactions. By attributing specific statements or questions to individual speakers, sales teams can gain a deeper understanding of customer needs, preferences, and pain points. This helps in developing personalized approaches, tailoring sales strategies, and nurturing stronger customer relationships.
a woman with curly hair and glasses talking to her phone and a woman with long straight hair talking on her laptop using headphones
  • Sales performance evaluation: Speaker diarization allows for objective evaluation of sales performance. By separating the voice of salespeople from customers or prospects, it becomes easier to assess sales techniques, pitch effectiveness, objection handling, and closing strategies. This information can be used to provide constructive feedback, identify top-performing salespeople, and share best practices across the sales team.
  • Sales meeting review and action items: Speaker diarization helps in sales meeting review and action item identification. By distinguishing speakers, it enables sales managers to identify who said what during team meetings, ensuring accurate attribution of action items or commitments. This aids in follow-up activities, tracking progress, and ensuring accountability within the sales team.
  • Sales analytics and reporting: Speaker diarization contributes to sales analytics and reporting by providing insights into sales conversations. By analyzing segmented speaker interactions, sales managers can identify patterns, trends, and successful strategies. This information can be leveraged to improve sales processes, refine sales approaches, and drive data-informed decision-making.


Speaker diarization finds applications in the healthcare industry, contributing to various aspects of patient care, medical research, and healthcare operations. Some popular examples include:

  • Medical transcription: Speaker diarization plays a role in accurate medical transcription. By separating the voices of healthcare professionals, patients, and other individuals involved in medical encounters, it helps in producing clear and organized transcripts of doctor-patient conversations, medical interviews, or surgical procedures. This aids in maintaining comprehensive and accurate medical records.
  • Clinical documentation and EHRs: Speaker diarization assists in documenting clinical encounters and updating electronic health records (EHRs). By attributing statements to individual speakers, it ensures that the correct information is recorded under the respective healthcare provider or patient. This contributes to the accuracy and completeness of medical documentation, supporting continuity of care and effective healthcare communication.
  • Telemedicine and remote consultations: Speaker diarization facilitates telemedicine and remote consultations. By separating the voices of healthcare professionals and patients, it helps in analyzing and documenting virtual visits or telehealth sessions. This allows for proper documentation, accurate diagnosis, and appropriate treatment planning in remote healthcare settings.
  • Medical research and clinical studies: Speaker diarization aids in medical research and clinical studies that involve audio data. By segmenting audio recordings and attributing statements to specific speakers, it enables efficient analysis and extraction of relevant information for research purposes. This can include identifying patient-reported outcomes, analyzing physician-patient communication, or evaluating the effectiveness of healthcare interventions.
  • Medical education and training: Speaker diarization is utilized in medical education and training programs. By separating the voices of instructors, clinicians, and learners, it allows for targeted feedback and assessment of learner performance. This facilitates the evaluation of communication skills, clinical reasoning, and adherence to protocols, contributing to the development of competent healthcare professionals.
  • Patient monitoring and compliance: Speaker diarization assists in patient monitoring and compliance efforts. By separating patient voices from healthcare provider voices, it helps in identifying patient-reported symptoms, treatment adherence, and compliance with care plans. This supports remote monitoring, medication adherence programs, and patient engagement initiatives.


Speaker diarization is also used in the field of education, enhancing various aspects of classroom instruction, online learning, and educational research:

  • Classroom transcription: Speaker diarization aids in transcribing classroom lectures and discussions. By segmenting the audio based on different speakers, it helps in producing accurate transcripts that attribute statements to specific individuals, such as teachers, students, or guest speakers. This supports accessibility, note-taking, and content review for students.
  • Interactive learning analysis: Speaker diarization allows for the analysis of interactive learning environments. By distinguishing between teachers and students, it enables the examination of participation patterns, turn-taking dynamics, or speaking time distribution. This provides insights into classroom engagement, instructional effectiveness, and student involvement in the learning process.
  • Online learning and captioning: Speaker diarization is valuable in online learning environments. It helps in generating captions or subtitles for educational videos, attributing spoken content to respective speakers. This aids in accessibility, comprehension, and language learning for students in asynchronous or distance learning settings.
  • Assessment and feedback: Speaker diarization supports assessment and feedback processes. By identifying individual speakers in oral assessments, presentations, or group discussions, it allows for targeted evaluation and feedback. Teachers can provide specific guidance, assess communication skills, and track student progress more effectively.
  • Research and education studies: Speaker diarization is utilized in educational research and studies. By segmenting audio recordings and attributing statements to different speakers, it facilitates data analysis, discourse analysis, or linguistic research. This supports the examination of teacher-student interactions, language acquisition, instructional strategies, or educational interventions.
  • Language learning and pronunciation practice: Speaker diarization aids in language learning and pronunciation practice. By separating the voices of native speakers and learners, it enables targeted analysis, comparison, and feedback on pronunciation, intonation, or speaking patterns. This helps learners improve their language skills and pronunciation accuracy.

Now you should have some ideas about speaker diarization’s definition, benefits, and use cases. Learn more about it in our next blog post that continues to explore more into speaker diarization.

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If you’d like to find out more about how StageZero works with speaker diarization or try out our annotation tool for free, contact us.

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