Approach to acknowledging the user when he/she is speaking with mmhmm, ahh, ok etc.

Does anyone know any open source projects or effective approaches for adding acknowledgements throughout the conversation?

I have an app where the user converses with the AI using his/her voice. When the user is talking, I want the AI to acknowledge what he/she said with ahh, mmhmm, ok to make the conversation more human.

I was thinking the AI acknowledges after each sentence or part of a sentence.. I’m wondering if there’s a more realistic approach than this that’s actually modeled after human conversations.