We have placed transitional audio prompt phrase for 45 seconds. Application getting host response in 5 mins .Till 160 seconds we could hear the content of transitional prompt, after that we are hearing blurred noise for 140 seconds, then application behaving as expected.

even though we have tried with creating transitional audio prompt phrase for 300 seconds. after 160 seconds we are hearing blurred noise.

Any recommendation on this issue would be appreciated.

I wondering if setting the Minimum Play Seconds property to 300s would change the behavior. It sounds more like a platform issue. You would need to contact Avaya Support.