In stage magic, what is often concealed to make objects seemingly appear from nowhere?

Which of these is a term used for a sudden, loud noise, linking 'boo' and 'boom' in effect?

What is a common association people have with the sound 'boom' in the context of film or video games?

Complete the phrase that is frequently associated with children's hide and seek games: 'Boo!' followed by...

What is a likely outcome if one mixes the ingredients meant to cause a 'boo' with that of a 'boom'?