Ive been listening to this sound clip too and just a few observations that are JMO. I may be wrong about these. Its just what I think I am hearing from this very short clip.
*I believe we are hearing footsteps spashing in shallow water
*I believe we are hearing wind too in the background
*to me it sure sounds like he has a mild accent of some kind. At the end of the word "there" is when it seems most noticeable to me.
I think he has a slight accent and the only thing that it resembles to me is maybe a slight british accent or possibly a slight canadian accent. I may be totally wrong and no offense to anyone. Its just what I think I am hearing from this very short clip. Below is the link to just the audio clip
http://www.in.gov/isp/files/Delphi_male_voice_loop.mp3
The last interesting thing to me is I believe we can hear slightly more in very front of the first part of the sound clip and its more noticeable when we hear it from the original news conference. If you listen to the sound clip when watching the video of the news conference there is a very brief 1/2 second of sound right before he says the first infamous "down there" and i think in the original news video it seems to come out better for some reason. The news video is in below news link.
At 00:30 is where they begin to play the sound clip in the video.
http://www.foxnews.com/us/2017/02/22/down-hill-indiana-girl-recorded-killer-in-chilling-audio-police-say.html
ETA I see where some and even the news story thinks he is saying "the hill" . I seem like I hear "down there". It just goes to show that I could very well be wrong. LOL
We need another bread crumb released to help with this case. Its so frustrating having so little to go on.