# Module 4: Voice, Language & Quality

**URL:** https://community.retellai.com/c/retell-university/module-4-voice-language-quality/49.md

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## [About the Module 4: Voice, Language & Quality category](https://community.retellai.com/t/about-the-module-4-voice-language-quality-category/2916)

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**Author:** [@system](https://community.retellai.com/u/system)\
**Replies:** 0

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## [Lesson 16: Guardrails & Safety](https://community.retellai.com/t/lesson-16-guardrails-safety/2934)

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**Author:** [@system](https://community.retellai.com/u/system)\
**Replies:** 0\
**Last updated:** [May 31, 2026, 1:52am UTC](https://community.retellai.com/t/lesson-16-guardrails-safety/2934 "2026-05-31T01:52:41Z")

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Guardrails & Safety Why Guardrails Matter AI agents can sometimes say things you don’t want them to In regulated industries (healthcare, finance), mistakes have real consequences Guardrails prevent the agent from going …

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## [Lesson 15: Knowledge Base Setup](https://community.retellai.com/t/lesson-15-knowledge-base-setup/2933)

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**Author:** [@system](https://community.retellai.com/u/system)\
**Replies:** 0\
**Last updated:** [May 31, 2026, 1:52am UTC](https://community.retellai.com/t/lesson-15-knowledge-base-setup/2933 "2026-05-31T01:52:40Z")

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Knowledge Base Setup A Knowledge Base gives your agent access to reference information it can use during conversations. What Is It? A collection of documents, URLs, or text that the agent can search during a call When …

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## [Lesson 14: Multilingual & Pronunciation](https://community.retellai.com/t/lesson-14-multilingual-pronunciation/2932)

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**Author:** [@system](https://community.retellai.com/u/system)\
**Replies:** 0\
**Last updated:** [May 31, 2026, 1:52am UTC](https://community.retellai.com/t/lesson-14-multilingual-pronunciation/2932 "2026-05-31T01:52:38Z")

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Multilingual & Pronunciation Multilingual Agents Retell supports multiple languages in a single agent Configure the primary language and allowed secondary languages Agent can detect the caller’s language and switch auto…

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## [Lesson 13: Voice Selection & Customization](https://community.retellai.com/t/lesson-13-voice-selection-customization/2931)

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**Author:** [@system](https://community.retellai.com/u/system)\
**Replies:** 0\
**Last updated:** [May 31, 2026, 1:52am UTC](https://community.retellai.com/t/lesson-13-voice-selection-customization/2931 "2026-05-31T01:52:37Z")

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Voice Selection & Customization Platform Voices Retell offers a library of pre-built voices with different: Gender — male, female, neutral Accent — American, British, Australian, Indian, and more Tone — professional, f…