Sentence:  These results deserve a brief discussion, because they contain the first indications about the "<WSD>unacoustic</WSD>" effects in shock reflection : That is, the deviations which shocks of finite strength present from the "acoustic" laws, which hold asymptotically for shocks of infinitesimal strength. 
Meaning of the word marked with <WSD> tags:  Having a frequency outside the range of audible sounds.