Does the Americans with Disabilities Act (ADA) require the city to use "certified" signers/interpreters?

Abstract: MTAS was asked whether the Americans with Disabilities Act (ADA) requires a city to use "certified" signers/interpreters. The response from MTAS was that the ADA requires interpreters to be "qualified," i.e., able to sign to the individual who is deaf those things that are being said by the hearing person and who can voice to the hearing person what is being signed by the individual who is deaf.