Google Adds Custom Tones and Voices to NotebookLM Audio Overviews

What just changed

Google has updated NotebookLM’s Audio Overviews—its podcast-like, AI-hosted summaries of user-supplied documents—to let users control tone and length. The new options let you choose the format of the AI podcast: Deep Dive, Brief, Critique, or Debate, and you can also pick from additional synthetic voices.

What each format delivers

• Deep Dive — Two AI hosts hold a conversational, question-driven unpacking of the material for nuanced exploration.
• Brief — A compact, punchy summary designed to get you the core ideas quickly.
• Critique — A constructive review that highlights strengths, gaps, and suggestions to improve the source material.
• Debate — Two AI hosts present opposing perspectives, useful for surfacing trade-offs and framing decisions.

Beyond tone, Google added controls for audio length so teams can tailor outputs for a quick commute listen or a deep review session. New voice options respond to a frequent user request and make the overviews feel more like produced podcasts than robotic readouts.

This update follows recent NotebookLM additions: Video Overviews that convert messy notes and PDFs into visual presentations, featured notebooks curated by researchers and organizations, and dedicated iOS and Android apps. Google says the new audio formats are rolling out in all languages this week.

Who benefits and why it matters

Students can convert dense readings into a debate to test critical thinking or a brief for quick review. Law firms and policy teams can produce critique-style overviews to flag weaknesses in opposing briefs. Product and design teams can use Deep Dives for post-mortems and cross-functional knowledge transfer.

But organizations should also weigh accuracy, citation, and confidentiality. Podcast-style outputs may smooth over uncertainty; teams need verification workflows and governance to prevent misrepresentation of sources.

How organizations should respond

Start with narrow pilots tied to specific outcomes: reduce prep time for classes, compress legal briefings, or speed onboarding. Define tone and voice playbooks so outputs align with brand and compliance. Measure usefulness with engagement metrics and accuracy checks before scaling.

At QuarkyByte we take a pragmatic, data-driven view: map user personas, simulate tone and length trade-offs, and set evaluation gates for factual integrity and privacy. The goal is not just shinier audio, but repeatable workflows that turn NotebookLM’s creative outputs into reliable knowledge assets for teams and institutions.

NotebookLM’s new tone presets and voices push AI summaries closer to everyday tools like podcasts and workshops. For teams, the question is how to adopt these formats so they accelerate decision-making without trading away accuracy or control.