how to do an instrument that can show soundwaves?

Question

we need this for our physics project. we need to design one. thank you

Answer 1

Try this:

Cut a balloon open, and stretch the rubber over the mouth of an empty glass jar. Secure the balloon with some strong rubber bands or tight string.

Find a small piece of a mirror (maybe 1/2-inch square). If you can't find an actual mirror that small, use a shiny metallic square of some other material. Glue the mirror to the middle of the stretched balloon.

Shine a bright light onto the mirror, so that the reflection falls onto the ceiling or a wall. Make sure the light is bright enough so that you can easily see the reflection as a small dot or square. If you have a laser pointer, that will work great; otherwise use a flashlight or a lamp. IMPORTANT: You need to secure the light in a fixed position; it's not good enough just to hold it with your hand. You need to secure the light so that the reflection doesn't move around on the wall.

Now your instrument is complete. To test it out, bend down near the face of the jar (don't block the light) and speak clearly directly to the balloon. This should make the balloon skin vibrate, and you should see the mirror's reflection "dance around" on the wall in response to the sound waves.

Answer 2

You might be able to hook up the output of a stereo to an ocilliscope, that should reflect the frequencies of the sound waves.