| Complexity level: | 7 |
| Project cost ($): | 80 |
| Time required: | 2 days to prepare, 1 hour for observation |
| Material availability: | Easily found. |
| Safety concerns: | None |
Hypothesis
Overview
Scientific Terms
Materials
Procedure
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.
Results
The higher density materials of glass and marble tile had the lowest noise level and plywood the lowest density material had the highest noise level recorded by the decibel meter.
Source of sound |
Density (kg/m3) |
Noise level (dB) of siren measured outside the box |
Noise outside box with the siren inside the box |
Plywood |
600 |
72 |
62 |
Bakelite |
1250 |
72 |
54 |
Glass |
2690 |
72 |
42 |
Marble tile |
2560 |
72 |
44 |
The graph below represents the results of our science project experiment.
