TRACY: I did a quick calculation on your test. The first mode resonant frequencies for two configurations and materials are listed below. The length is the length extending out past the clamped end.
MATERIAL LENGTH (INCHES) RESONANT FREQUENCY (Hz)
ALUMINUM 2 49168
ALUMINUM 1.5 87410
STEEL 2 47207
STEEL 1.5 83923
If I did the math correctly we see that the 170 Hz is well below the resonant frequency of the beams. Your method of computing the "Q" is incorrect. I suggest that you use a much longer beam, say somewhere around 24 to 36 inches, you will be in the 200 - 300 Hz range for the resonant frequency.
See any vibrations text on how to compute Q.
Hope this helps