To me this sounds exactly like Kari received a call while at home, and put him on speakerphone while recording the call with a separate device sitting on her desk. His voice has a speaker quality, and reverbs around the room as it was turned up loud. Her voice is clear and direct to the recording device in her natural speaking volume. If a call recording app was used you'd hear clearer voices on both ends without the room reverb.

Edit: Now I've heard the recording that sounds like they are both in the same room, perhaps a reflective kitchen area. The recording device is clearly closer to Kari.