Talking into one end of an empty coffee can vibrates a small mirror that is cemented to a stretched rubber balloon over the opposite end of the coffee can. A laser pointer is mounted on a bent curtain rod section so its beam strikes the mirror and is reflected to a distant screen. Interesting and recognizable patterns of light can be generated on the screen in response to any loud sounds entering the coffee can.

Components

• 1 empty coffee can, top and bottom removed
• 1 flat telescoping curtain rod.
• 1 round rubber balloon, 5 to 10 cm diameter before inflation
• 1 piece of thin front-surface miror, approximately one square centimeter
• 3 rubber bands
• 1 laser pointer
• Rubber cement or a small piece of double-stick tape.

• 1. Cut off the neck of your balloon and stretch the rest of it over an end of your coffee can. Secure it with one or more rubber bands.
• 2. Separate the two sections of your flat telescoping curtain rod. With a hack saw, cut off a length of approximately 20 centimeters from one of the two sections. The remainder of the curtain rod may be discarded. Place the cut-off section over the edge of a table, flat side down. Position it so only half of its length rests on the table and the remainder extends beyond the table edge. Apply pressure to bend the free end down at an angle of approximately 45 degrees. Tape the bent curtain rod section to the outside of the coffee can as shown in the diagram.
• 3. Mount your laser pointer in the position shown in the diagram and secure it with rubber bands.
• 4.Turn on the laser pointer and cement the small piece of mirror over the point illuminated by the laser beam. This completes the apparatus assembly