At one time there were several tuning forks that were paired with hollow, cylindrical brass resonating chambers, as in figure 3. These beautiful forks seem to have been the reference standards for the musical scale. The only surviving member of the collection of such forks is a “middle” C 256 Hz fork, though there is another such chamber that is meant specifically for a 64 Hz driven fork. Figure 3 shows the standard A of 440 Hz. The tuning fork is mounted by its threaded end to the stand so that the tines are very close to but do not touch the end of the chamber. The chamber has a vertical rectangular opening in its end which is about 20% wider than the distance between the tines of the tuning fork. The author found that if the fork is mounted so that the one can see into the brass chamber (as in figure 3), the tone when the fork is struck has a higher volume, while if the fork is turned 90°, the tone will be audible for a longer time because the standing wave that the fork generates inside the resonance chamber will act to preserve the fork’s motion.
tuning spoons, forks and knives