Rotate Robot head according to Sound level
A couple of years ago, I completed a MOOC on FUN called Binaural Hearing for Robots (it doesn't seem to have run since, but it may be worth keeping an eye on it to see if they open registration again. At least some of the resources seem to be archived here). Interestingly, localising sound turns out to be easier with three microphones than with two.

You scan the three inputs in sequence, and when the sound is directed to record the time-difference between the three sensors. The technique you're looking at to localise the source is called trilateration.

Once you have a direction relative to the robot head, you can use a simple servo to turn the robot head to that direction.

I did play around with this a little bit, using three KY-038 microphone modules like this that I picked up cheap on eBay:



Connect them to your Arduino something like this:





I can't find my code (it was pretty untidy anyway since I was just playing around while I was working on the course), but a lot of Arduino sound-localisation projects have been published online with examples easy to find on Instructables, Hackaday, and many other sites.