Hold the ruler horizontally and 1 inch from your ear. It should be sticking out long-ways, 1 inch from your ear. Now scratch the far end of the ruler with your fingernail. Listen to the sound and note how loud it is. Then move the ruler 13 inches away from your ear and scratch the end closest to you. (This way both scratches will be the same distance from your ear both times.) Note the difference in your journal with a dated entry. Include an explanation of your observation.

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