If the patch "gcc-6" is not applied, the package at least compiles. It still fails to build with the following error though:
debian/rules override_dh_installdocs
make[1]: Entering directory '/build/speech-tools-2.4~release'
dh_installdocs -pspeech-tools -plibestools2.4 -plibestools-dev README
dh_installdocs -pspeech-tools-dbg -plibestools2.4-dbg -pspeech-tools-doc
dh_installdocs: Requested unknown package speech-tools-dbg via -p/--package, expected one of: libestools2.4 libestools-dev speech-tools speech-tools-doc
dh_installdocs: Requested unknown package libestools2.4-dbg via -p/--package, expected one of: libestools2.4 libestools-dev speech-tools speech-tools-doc
dh_installdocs: unknown option or error during option parsing; aborting
debian/rules:137: recipe for target 'override_dh_installdocs' failed
make[1]: *** [override_dh_installdocs] Error 25