IPA: /əˈkuːstɪkəl/
KK: /əˈkuːstɪkəl/
Related to sound or the science of sound, especially how it is heard or produced.
The acoustical design of the concert hall enhances the sound quality of performances.
Acoustical is formed from "acoustics" (from Greek "akoustikos", meaning of or for hearing) and the suffix "-al" (meaning pertaining to). The word "acoustical" refers to something that pertains to sound or hearing.
Think of 'hearing' ('akoustikos') when you remember that 'acoustical' relates to sound.