A bright red semitrailer truck lures children, who will have to supply their own sound effects when they pretend to drive the rig at the Children's Museum. The horn has been disconnected, to preserve the sanity of the museum staff and parents. The little ones don't seem to mind. Just ask Aubrey Ann Haliday, who checks it out with the museum's Richard Morris, above. Pretending is all part of the fun at the display which opened this week at the Children's Museum of Utah, 840 N. 300 West, Salt Lake City. Hours are 9:30 a.m. to 9 p.m. on Monday; 9:30 a.m. to 5 p.m., Tuesday through Saturday; noon to 5 p.m. on Sunday. Mr. and Mrs. J. E. Treadway of Kenilworth Sales donated the truck cab. Wayne Geary painted the mural behind it.