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Overview

English phoneme control uses CMU Arpabet, the pronunciation format used by CMUdict. Wrap the pronunciation for one word in <|phoneme_start|> and <|phoneme_end|>, and keep surrounding punctuation outside the tag. 
I am an <|phoneme_start|>EH1 N JH AH0 N IH1 R<|phoneme_end|>.
IPA is not supported for English phoneme tags. Convert IPA pronunciations to CMU Arpabet before using phoneme control.

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CMU Arpabet

CMU Arpabet is written as space-separated uppercase symbols. Vowels can include stress digits:
  • 0 for unstressed vowels.
  • 1 for primary stress.
  • 2 for secondary stress.
For the full symbol inventory, see the CMUdict cmudict.symbols list. You can also look up words on the CMU Pronouncing Dictionary page. Example: 
Standard: I am an engineer.
With phoneme control: I am an <|phoneme_start|>EH1 N JH AH0 N IH1 R<|phoneme_end|>.
You can omit stress digits when you only need a rough pronunciation, but CMUdict-style output with stress digits usually gives the model the clearest signal.

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Common Examples

Use phoneme control when spelling alone is ambiguous: 
The <|phoneme_start|>R IY1 D<|phoneme_end|> endpoint returns the current state.
The book was <|phoneme_start|>R EH1 D<|phoneme_end|> yesterday.

The <|phoneme_start|>B EY1 S<|phoneme_end|> line is too loud.
The <|phoneme_start|>B AE1 S<|phoneme_end|> swam upstream.

The <|phoneme_start|>P OW1 L IH0 SH<|phoneme_end|> team joined the call.
Please <|phoneme_start|>P AA1 L IH0 SH<|phoneme_end|> the final mix.
Use it for product names, acronyms, and technical terms: 
Deploy with <|phoneme_start|>K UW2 B ER0 N EH1 T IY0 Z<|phoneme_end|>.
The query uses <|phoneme_start|>EH1 S K Y UW1 EH1 L<|phoneme_end|>.

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Generate CMU Arpabet

The training pipeline uses CMUdict-style pronunciations. You can generate the same format with the cmudict package: 
pip install cmudict

import cmudict


entries = cmudict.dict()


def cmu_pronunciation(word: str) -> str | None:
    phones = entries.get(word.lower())
    if not phones:
        return None
    return " ".join(phones[0])


print(cmu_pronunciation("engineer"))
# EH1 N JH AH0 N IH1 R
CMUdict may contain multiple pronunciations for the same word. Listen to the result and choose the variant that matches your intended accent or context.

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Practical Tips

  • Replace only the word whose pronunciation needs control.
  • Strip punctuation before dictionary lookup, then place punctuation after the tag.
  • Use CMU Arpabet for English phoneme tags.
  • For names and brands, write the pronunciation that you want the listener to hear, not necessarily the spelling.