Material density and sound transmission
The 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 to slide in 250mm x 250mm boards of thickness 5mm on one side only.
- A 250mm x 250mm piece of plywood of 5mm thickness
- A 250mm x 250mm 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 experiment, the independent variable is the type of medium used as 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 source of the sound and the distance of the decibel meter from the box.
2. One plywood box is made in the workshop or ordered from the local carpenter. For this experiment the size of 300mm x 300mm x 300mm is proposed but other dimensions can also be used. The top cover of the box should be removable to place the source of the sound inside the box and to replace the sound barrier medium on the front side of the box as shown in figure 1 below.
3. The siren is set to ring 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 set to ring again and placed inside the box with the plywood medium. The top cover of the box is closed and the decibel meter is placed 500mm from the plywood board to measure the noise. The measurement is recorded in the table.
5. Procedure 4 is repeated after replacing the plywood board with the bakelite board, glass and marble tile in turn.