acoustic(pertaining to hearing or the science of sounds) adjective [UK: əˈk.uː.stɪk] [US: əˈk.uː.stɪk]He plays the acoustic guitar with great mastery. = Toca la guitarra acústica con gran maestría.
acoustical(of or pertaining to hearing or acoustics) adjective [UK: əˈk.uː.stɪkəl] [US: əˈk.uː.stɪkəl]