Use \refmodule when we say "use the XXX module instead".
For the whatsound module, point to sndhdr.
diff --git a/Doc/lib/libundoc.tex b/Doc/lib/libundoc.tex
index 5d1b3ca..4420468 100644
--- a/Doc/lib/libundoc.tex
+++ b/Doc/lib/libundoc.tex
@@ -220,14 +220,14 @@
\item[tb.py]
--- Print tracebacks, with a dump of local variables (use
-\function{pdb.pm()} or \module{traceback} instead)
+\function{pdb.pm()} or \refmodule{traceback} instead)
\item[timingmodule]
--- Measure time intervals to high resolution (use
\function{time.clock()} instead). (This is an extension module.)
\item[whatsound.py]
---- recognizing sound files
+--- Recognize sound files; use \refmodule{sndhdr} instead.
\item[zmod.py]
--- Compute properties of mathematical "fields"