# All Science Fair Projects

## How does the size of a speaker affect its frequency response

### Materials

The materials required for this science fair project:

-    3 pieces of plywood measuring 1meter x 1meter
-    Hammer and nails (quantity as required)
-    Glue
-    Silicon filler
-    Three 8-inch speakers
-    Electric drill and drill bits
-    Saw
-    Decibel meter
-    CD player
-    Test CD with various audio frequencies

### Procedure

1.    For this experiment, the independent variable is the side of the enclosure and audio frequency played. The dependent variable is the decibel reading of the frequency. The reading is measured using a Decibel meter. The constants (control variables) are the materials used to construct the speaker, the size of the speaker and the distance of the decibel meter from the speaker.

2.    The plywood planks are cut and constructed according to the speaker enclosure sizes shown in figure 2. The speakers are marked A for 500mm depth, B for 400mm depth and C for 300mm depth. The plywood planks are constructed into the enclosure sizes using glue and nails.

3.    The areas where the two plywood pieces meet are sealed using silicon filler to make the enclosure air tight. Using a drill and  saw, an 8-inch hole is cut in the center of the enclosure to mount the driver.

4.    A small hole is made at the back of the enclosure using the drill. The wire from the speaker driver is taken out through this hole and connected to the CD player.

5.    The decibel meter is placed 1 meter in front of the speaker A. The speaker wire from enclosure A is connected to the CD player. The CD player is made to generate audio sounds at 30Hz, 50Hz, 80Hz, 150Hz, 300Hz and 600Hz. The reading on the decibel meter is recorded in the table below.

6.    The procedure above (Step 5) is repeated using speaker B and speaker C. The results are all recorded in the table below.

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Complexity level:
7
Project cost (\$):
90
Time required:
2 days to prepare, 1 day for experiment
Material availability:
Easily found. May be purchased at a hardware store (eg. Home Depot)
Safety concerns:

None