The Horn and Whistle Board

Hi all I have an interesting question about 4449's Hancock. Why does it sound so much different than all the other Hancock 3 chimes out there? Take for example the Union Pacific's 844 which also has a Hancock 3 chime they sound entirely different! the 4449's sounds much more melodious (to me anyway) anybody know why this is?

The sound and performance of a whistle are dependent on its working dimensions. Are the working dimensions of this Hancock different from others? That is the key. Is there a difference in the working lengths? Also, is the lip of the bell concentric with the slit? All of this would make an audible difference.

As far as I know both whistles are plumbed to superheaters and are blown at 300 psi. I have sampled recordings of those whistles dating back some time and they generally blow a major chord or close to it, but can sound a bit different each time they are blown, like due to some variation in temperature and flow. Steam whistles are fickle instruments. If the whistles are plumbed with a gate valve maybe the setting varies from run to run.

Here are some samples recorded on different occasions:
844:
256-315-385 Hz
246-302-378
251-310-380
256-315-380

4449:
256-304-364
256-326-380
251-310-358

Yes I am aware of the dimensions and lengths determining sound but I was unaware that Hancock offered the 3 chime in different sizes like some of the more common whistle companies.

Still another explanation could be that the whistles were not built to close tolerances and each was not an exact copy of the other. We see enough of this in air horns. Don't we? If the languid plate, for example, was not concentric with the bowl, it would result in a non uniform slit width. This would cause a difference, such as you mentioned if the different chambers of the bell were not aligned in the same way and if the slit width non uniformity was the same on both whistles. And all of this even assumes that the bells of both whistles are identical!!

For two whistles to sound alike they need to be identical copies built to close tolerances and operated on the same medium at the same pressure and temperature. This was rarely, if ever, the case.

Exactly. Here are two stock 4-inch diameter Buckeye chimes that I sampled blowing side by side at the same time on the same manifold:

391-450-535
403-463-546

Out of interest, here is the Hancock on NW 611 at 300 psi on saturated steam:
259-321-383

Very similar to the blow on the superheater. Superheated steam has higher temperature (which raises frequency) but the higher temperature reduces the flow rate of the steam to the whistle (which lowers frequency). The difference in flow rate can be calculated if you know the degree of superheating. But have to figure in radiant loss, reduced density (increased specific volume to the whistle) so it would be a tough calculation. In the comparison we have in this situation with these locomotives, there was little difference between saturated and superheated.

All I know is that 4449 has the best-sounding whistle out there.