What's the function of a 'sound trap'?

[Sarah Crow]

Hello
I've been delving into the world of organ blowers, following my last query to expert organ builders on this forum. Thanks so much for your help - it's been invaluable!

I've been looking at the designs of blowers plus silencers from Meidinger. The silencing method looks very interesting and I'm wondering what the purpose of the 'sound trap' is? I'm assuming it's to reduce sound levels somehow. It looks to me like a resonant cavity of some sort that you can open or close.

I'm new to the world of organ building so if anyone can enlighten me to its exact function and the physics of how it works, I'd be very grateful.

Thanks!

Sarah

[Terpodion]

The sound trap works on the principal that any time a sound wave bounces off an object it loses something. In a sound trap the idea is to present the sound wave with a space which it can not escape without reflecting off surfaces multiple times, thus dissipating most (ideally all ) of its energy. The most famous use of this is by the innovative builder Robert Hope Jones. His expression shades had a "sound trap joint" along each opposing edge.

[VaPipeorgantuner]

the reason for a sound trap on a blower line is eliminate as much of the wind noise as possible that is generated by turbulence created by the fan blades. Usually this is in the form of a baffle box with several dividers internal to the box. These baffles are usually lined with thick felt. The felt itself acts as an acoustical damper and the several turns in the air path tends to smooth out the fan turbulence that is fed into the wind system of the organ. properly installed, these are pretty effective.

Rick in VA

[Sarah Crow]

Thanks so much both of you - this is really useful. Am now drawing out a soundtrap design!