/usr/include/speech_tools/ling_class/ is in libestools2.1-dev 1:2.1~release-6.
This file is owned by root:root, with mode 0o755.
..
/usr/include/speech_tools/ling_class/EST_FeatureFunctionPackage.h
/usr/include/speech_tools/ling_class/EST_Item.h
/usr/include/speech_tools/ling_class/EST_Item_Content.h
/usr/include/speech_tools/ling_class/EST_Relation.h
/usr/include/speech_tools/ling_class/EST_Relation_list.h
/usr/include/speech_tools/ling_class/EST_Relation_mls.h
/usr/include/speech_tools/ling_class/EST_Relation_tree.h
/usr/include/speech_tools/ling_class/EST_Utterance.h
/usr/include/speech_tools/ling_class/EST_item_aux.h
/usr/include/speech_tools/ling_class/EST_item_content_aux.h
/usr/include/speech_tools/ling_class/EST_relation_aux.h
/usr/include/speech_tools/ling_class/EST_relation_compare.h
/usr/include/speech_tools/ling_class/EST_utterance_aux.h
/usr/include/speech_tools/ling_class/EST_utterance_xml.h