acousticofacial

The story

1. Proto-Indo-European*h₂eḱ-
2. Proto-Indo-European*h₂ew-
3. Proto-Indo-European*h₂ṓws
4. Proto-Indo-European*h₂ḱh₂owsyéti
5. Proto-Hellenic*akóuhō
6. Ancient Greekἀκούω (akoúō)
7. Ancient Greekᾰ̓κουστῐκός (ăkoustĭkós)
8. Medieval Latinacousticus
9. Englishacoustic
10. Proto-Indo-European*dʰeh₁-
11. Proto-Indo-European*dʰeh₁k-
12. Proto-Indo-European*dʰh₁kyéti
13. Proto-Italic*θakjō
14. Proto-Italic*fakjō
15. Latinfaciō
16. Latinfaciēs
17. Proto-Indo-European*h₂el-
18. Proto-Indo-European*h₂élisder.?
19. Medieval Latinfaciālis
20. Englishfacial
21. English todayacousticofacial

From acoustic + -o- + facial.