1. (a) Powered air-purifying respirators must be designed to allow for proper communication while worn.
2. (b) A Modified Rhyme Test ⁷ will be used to test the wearer's ability to communicate efficiently.
3. (c) The communications requirement is met if the overall performance rating is greater than or equal to 70 percent.

⁷ The Modified Rhyme Test is used in speech intelligibility experiments. See https://www.nist.gov/ctl/pscr/modified-rhyme-test-audio-library.