Material density and the transmission of sound
science fair projectThe materials required for this science fair project:
- A decibel meter for measuring noise
- A battery operated siren
- A 300mm x 300mm x 300mm plywood box with slots carved into its side, for us to slide in a 250mm x 250mm board of thickness 5mm on one side only.
- A 250mm x 250mm sheet of plywood of 5mm thickness
- A 250mm x 250mm sheet of bakelite of 5mm thickness
- A 250mm x 250mm sheet of glass of 5mm thickness
- A 250mm x 250mm marble tile of 5mm thickness
- A ruler
1. For this science fair project, the independent variable is the type of medium used as a sound barrier. The dependent variable is the noise level outside the box, measured using a decibel meter. The constants (control variables) are the size of the plywood box, the sound source and the distance of the decibel meter from the box.
2. Have a carpenter assemble the plywood box for you. For this science project experiment, the size of 300mm x 300mm x 300mm is proposed but other alternative dimensions may be used. The top cover of the box should be removable, in order to allow you to place the sound source inside the box and to replace the sound barrier on the front side of the box as shown in figure 1 below.
3. The siren is turned on and the noise level is measured using the decibel meter placed 500mm away from the siren. The readings are recorded in the table below.
4. The siren is turned on again and placed inside the box with the plywood medium. The top of the box is covered and the decibel meter placed 500mm from the plywood board to measure the noise level. Record your readings.
5. Procedure 4 is repeated after replacing the plywood board with the bakelite board, glass and marble tile in turn.
Handle breakable/heavy materials carefully. Ensure that you wear protective gloves.