To cite package ‘signal’ in publications use:

  signal developers (2023). _signal: Signal processing_.
  <https://r-forge.r-project.org/projects/signal/>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {{signal}: Signal processing},
    author = {{signal developers}},
    year = {2023},
    url = {https://r-forge.r-project.org/projects/signal/},
  }