Here's a round about possible source. On Kanopy.com there is a two part video on a recent study of H. Neanderthalensis; a part of which has a segment on Sapiens and Neanderthal speech by a noted researcher. The video is simply entitled "Neanderthal". That researcher's work may have more detailed data than was in the video which might suit your inquiry. So watch the video and contact the speech researcher. Note: In my area, Kanopy.com is free via a local library card. As I remember the video was a 2018 PBS production and may be readily available from other sources. Search on "Neanderthal"