It’s time to pull out an album from your record collection or pick up one from a thrift store! Grab a partner and some simple supplies and you can make a turntable to listen to a vinyl LP without electricity. This activity teaches aspects of engineering and technology, and the physics behind sound waves. Thank you Eli and Kate Carlson for submitting your project and being this week’s Arts Quincy STEAM Stars!
How Does It Work?
A record is a sculpture of sound. Every record has grooves in it that have tiny bumps and bends that correspond to the recorded music. As the record turns, the tip of the pin follows within the spiraling groove, following the bumps and bends which makes the pin (and the paper cone) pulsate up and down and side to side. The vibrations inside the cone cause the air to vibrate which then radiates out of the cone into your ear so you can hear the music!
A sharpened pencil
A narrow sewing pin
Sheet of paper
Make the turntable
Place the pencil through the middle of the record so that it stands upright and can spin as if it were on a normal turntable.
Wrap tape around the pencil just below the record so the pencil doesn’t slip back through the center hole.
Test the assembly by twirling the pencil. The record should turn with it. If not, apply more tape as needed to secure the pencil and each piece doesn’t turn by itself.
Make the needle arm and sound cone
Take one corner of the piece of paper and roll it diagonally to form a cone shape. The tip of the cone should be completely closed. Tape the paper in place to keep the cone from unrolling.
Push the pin through both sides of the paper about half an inch from the tip of the cone so it sticks out at a 45-degree angle. Use tape to secure the pin if you need to.
Set up the turntable
Two people are required for this activity to work correctly. One person will rotate the turntable and the other will hold the needle arm and sound cone.
Set up the turntable by holding the pencil and record assembly point-side down (like a spinning top) on a table or sturdy surface. The pencil will act as the axle. Keep the record as horizontal as possible. Gently twirl the pencil and turn the record clockwise. Try to spin the record at 33.3 revolutions per minute (RPM), good luck!
To set up the needle arm, hold the wider end of the sound cone and bring the pointed end of the cone, with the pin hanging down, close to the record. The needle arm should be parallel to the groove (see picture above). To get a consistent sound, the pin needs to rest comfortably in the groove as the record rotates beneath it.
Now you’re ready to listen!
Lower the pin so that it rests in a groove of the spinning LP. Gently hold the top of the cone with the weight of the cone being supported by the pin which will allow it to move along with the motion of the spinning record. Listen to the sound that comes out of the open end of the paper cone. With the right speed, you should hear the music!
STEAM activity credit: exploratorium.edu.