|MadSci Network: Other|
Dear Sarah, I'm not surprised your K-3 students are a bit confused by pitch. The definition of pitch is quite hotly debated among scientists who study hearing. In general though, pitch varies with frequency. When one blows across the top of a pop bottle partially filled with water, pressure waves of air are created inside the bottle. The pressure waves vibrate at a certain frequency (i.e., they go through cycles of high and low pressure a particular number of times per second -- high frequencies cycle faster than low). The frequency depends upon the shape of the bottle, which can be varied by changing the water level. In general, for longer bottles and for less water, the air pressure waves will vibrate at higher frequencies. The frequency of air pressure vibration is a physical occurrence that can be measured. Pitch, however, is a psychological term for how our ears and brain interprets those frequencies. Pitch is not exactly the same thing as frequency. However, generally speaking, higher frequencies are heard as higher-pitched than lower frequencies. The relationship between the frequency and pitch isn't perfect (which gives scientists lots to argue about), but it is close enough to be taught in general terms. If I can answer more question you might have, please feel free to email me directly email@example.com. Lori Holt Administrator's note: If my memory is correct, the volume of a bottle is the key factor in the frequency that it will produce. You might want to do an experiment to see if a long thin bottle will sound the same as a fat bottle of the same length. Experiments are good for the growing scientific mind. David Winsemius
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