My recently acquired 1950 Elgin 571 in the picture below has very little wear to it, keeps excellent time, but ticks very loudly in comparison to my 1952 Vanguard shown, or any Hamilton 992B I have bought.

My wife noticed the ticking sound coming from my pocket from 4 feet away. I can imagine other people noticing it too, in a quiet room.

My question: What makes a particular model tick louder than other watches?

I have three of these (each version) and I don't think they are super loud but I have had some watches that even with my hearing I thought it was a bit loud. Your appears to be the first version, marked 8 adjustments, no BWR marking on the movement and only the dP logo on the dial (dura-power)and everything else looks correct from what I see in the picture.

I think the 571 gets a bad rap because people comment that the setting mechanism was suspect but I think many were damaged because people did not know how to remove the stem properly or tried to set the hands by pulling on the crown.

Claude, here is a picture of the movement to help the identification. While we are at it, Claude, can you tell if the center wheel is solid or plated?

The center wheel is solid brass.

The "Tick" sound in a watch is caused by the pallet fork striking the banking pins as it oscillates back and forth to engage and add force to continue propelling the balance wheel through its full arc of rotation between each escapement cycle.

These banking pins are normally screwed or pressed into the dial plate. The dial plate WILL act as a "sounding board" for the sound of the pallet fork strike which can vary in amplitude for many reasons.

If you put a stethoscope to the watch you can also hear other sounds that reflect the other mechanical ringing and clunking of various components.

My "guess" for the 571 being louder than the Waltham is two-fold;

A; The Vanguard has a safety (motor) barrel that imparts a lower torque thrust to the escape wheel, reducing the strike intensity of the pallet fork that is absorbed by the banking pin.

B; The placement of the banking pins on the Vanguard are closer to the pallet fork pivot making the "strike" a quieter event. Kind of like when a batter hits a baseball ("Thump") near the grip end of the baseball bat so you do not hear that resounding "Crack" that comes from a home run hit off the long end of the bat.