The Best Archiver

[ZiNgA BuRgA]

For WinRAR, just choose Best RAR, and tick the Solid compression checkbox.  Solid compression only is used if you're compressing more than one file though, so in your above case, it won't make a difference enabled or disabled.

32-bit (single precision float?) WAV is a bit unusual as a file you'd distribute - usually they'll be 16-bit, or in some not-so-often cases, 8-bit or 24-bit.

PPMd is designed for text compression, so I'm surprised how well it did with your WAV sample.  UHARC usually beats 7-Zip, but of course, at the expense of speed.  I'm also unsure if the algorithm is really optimised since it doesn't seem to have undergone as much development as LZMA, so maybe there's more speed potential in it.
RAR generally beats LZMA at media compression (see also this guy's comparison) - this probably also includes images, as well as already compressed data (LZMA doesn't seem to handle compressed data well - this issue was fixed in LZMA2 which can store uncompressed blocks).  I guess your example shows where RAR doesn't beat 7-Zip.