Here is a clever thing to do. Get some call abandon data from your system and plot a call abandon curve. This starts with 100% of callers at 0 seconds of queueing and goes down over time.
You may find that you get large numbers of callers after certain messages are played.
One contact centre that I spoke with was able to reduce its abandoned percentage from 7% down to 2.9% simply by changing one of the IVR messages. (It tends to be the second one that is the culprit.)