For me the best way to put plastic cups or boxes (thin-walled) in your ultrasonic bath. fill them with same liquid  and up to same level liquid as into bath. Put ice cube inside cups or box. So you will divide the water from ice and liquid into bath. a thin wall is not an obstacle for ultrasonic waves.... 

Hi Oleg, thanks for the answer.

Will the ultrasonic bath generate abnormal sound or spoil if I place ice cubes directly into the ultrasonicator water bath?

Thank you. 

Hi, Chingyeh Ong

We use only this method for prevention any contamination (usual procedure is part cleaning ) . Possible you can see my attached picture

Best regards