Geluid (Sounds) is a Sesamstraat episode that first aired in September 20, 1989, during the 13th season.
After hearing an airplane in the sky, Lex plays a guessing game with Tommie and Ieniemienie, and has them guess the different sounds he makes (including a vacuum, a toilet, and a teacup). During the game, Paula stops by with a jar of cookies, but not after Lex also has the kids guess her surprise as well.
Frank is blindfolded by a group of schoolchildren, who challenge him to the same guessing game on sounds.
Grover: Grover has a box that can make the sound "ding-ding". However Grover can't make it to sound right so he attempts to fix it. When it's fixed and says "ding-ding", Cookie Monster comes because he thinks he heard the dinner bell ring and eats the box.