Some bikes make a subtle clicking noise and some make a God awful noise in freewheel. Why?

A guy snuck up behind me a couple weeks ago a made me jump when he started gliding. I thought I was being run over by a weird sounding vehicle.

Why are some quiet and some unroost the birds?

They all generally work the same way, but different manufacturers use different numbers of pawls, different springs, etc. Shimano tries to make theirs quiet. My somewhat perverse rule-of-thumb is that the more expensive the hub or freewheel gets, the louder it is.

The freewheel on my trail bike is silent, while the Zipp 303s are really loud.

Chris King freehubs are ridiculously loud, so you may be on the right track.

Based on my experience your "somewhat perverse rule-of-thumb" is spot on.

Rick / OCRR

It used to be - many years ago - that 105's were pretty quiet and Dura Ace were loud. However, I am reaching far back.

Mine too. I wonder whassup with that?

My 3 Velocity (Chosen?) hubs: 1 quiet, 1 moderate and one a bit loud.
This Brit shows how to improve (!!!) the noise level of a Chris King freehub. (cut to near the end)
https://vimeo.com/5113301

The older Chris King Classic hub is very loud (my spare wheel set has these hubs). From what I read, the newer King hubs are not as loud. They use a "Ring Gear" instead of pawls.

When I do the routine maintenance on my Phil Wood freehub, if I put a bit of grease on the pawls per the manufacturer's recommendation they become extremely quiet. Right now they are deafening, but since the frame is going in to be painted soon, I'll take care of that while the bike is out of service.

Older Hugi hubs used ramped ring gears instead of pawls and were plenty loud.

Combination of design and lubrication. Put thick enough lube in the hub and it will quiet down.

Lightweight freehubs have fewer paws and deeper ramps, hence the load mechanical noise.

I have a White Industries T11 hub and a camp free hub body. It is quiet, very quiet. I have a set of Mavics on the other bike with a campy free hub body. It is loud.

Large-bore carbon fiber frames and deep rim wheels seem to amplify the ratchet noise.

I was pulling into a park last week to take a break, and a woman told me that my clicking was really loud and it was cool, she also said that at first she thought it was her young son riding before she was ready since he had a playing card in his spokes.

Personally I prefer quieter freewheels and free hubs.

A little grease will help a great deal in the freewheel and unfortunately carbon fiber frames and rims amplify the unpleasant noise!

There is silent freehubs made for the Cop's Bikes *, to sneak up on suspects..

*Probably un needed for the guy with the chalk on a Stick, marking your parked car's tires.

Modern bikes have hella noisy cassettes. That's just the way they are. Want the normal/old school sound? Get an older bike.

It depends on the number of pawls, the type of springs, the shaping of the pawls, and the grease used. Even the alloy used for the parts makes a difference. I agree with BP, also, probably related to the more expensive hubs being made of good, strong alloys, the springs being stronger and in most cases, more pawls for a stronger, faster engagement. The old style freewheels were a totally different sound to me, from the current hub and cassette set up.

Bill

The Dura Ace 7700 25th anniversary hubs on my Lemond are pretty much silent. By far the nicest of any wheels I've owned. They surprised me by being so silent when i picked up the bike.

Campagnola as a brand has always made a louder clicking freewheel sound then most other manufacterers. My 10 speed ultegra hubs are very quiet.

For a short while

My wife has a completely silent freehub. It creeps me out.

I think the sound is strictly a secondary aspect of the design. The design instructions given to the engineer probably say "the freewheel or freehub shall include a ratchet to ensure one-way drive" and say nothing about noise. Strictly a side effect.