When no contrast is employed, harmonics are generated by tissue itself as a result of nonlinearpropagation.
当不使用造影剂时，谐波是由非线性传播产生的。
2
A novel audio beam loudspeaker is fabricated by utilizing the nonlinearpropagation effects of ultrasonic in the air to generate audible high directivity sound.
一种新颖的声束扬声器是捏造的利用超声波在空气中的非线性传播效应，产生声音的高指向性的声音。
3
A novel audio beam loudspeaker which based on nonlinearpropagation effects of ultrasonic in the air to generate audible sound with high directivity is presented.