MadSci Network: Other

Re: I am looking for a good working definition for pitch.

Date: Sat Feb 7 16:50:37 1998
Posted By: Lori Holt, Graduate (Ph.D.) Student, Psychology, Ph.D., University of Wisconsin
Area of science: Other
ID: 886450183.Ot

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 

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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