To cite ipa in publications use:

  Alexander Rossell Hayes (2020). ipa: convert between phonetic
  alphabets. R package version 0.1.0.
  https://github.com/rossellhayes/ipa

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {ipa: convert between phonetic alphabets},
    author = {Rossell Hayes and {Alexander}},
    year = {2020},
    note = {R package version 0.1.0},
    url = {https://github.com/rossellhayes/ipa},
  }