The Helmholtz Resonator

As some of you know, good German engineering is something that really excites me, and I’m happy to say that for the major project for the MBR National Park, I’ve been able to riff on the acoustic design of a fascinating late 19th century German engineer named Hermann von Helmholtz. Helmholtz invented the ‘Helmholtz resonator’ (drawing above) to identify the various frequencies or pitches of the pure sine wave components of complex sounds containing multiple tones. Here is an example of how a series of various size resonators would be arranged for acoustic analysis, your ear would go into the small tube at the front:

For those of you who are interested in the physics of this concept here is an explanation:
http://www.phys.unsw.edu.au/jw/Helmholtz.html

and an online calculator to determine the resonant frequency based on the size of the sphere and hole:
http://www.vk2zay.net/calculators/helmholtz.php

The basic concept of the Helmholtz resonator, a resonant chamber with a hole, is used in many if not all musical instruments, with variously sized chambers adding to the complexity of the sound. For example, the combination of four primary resonant chambers and specially shaped ‘f’ holes in a violin body contribute to the beauty and complexity of the resultant sound of the instrument.

Other contemporary uses of the resonator are in dampening or reducing certain frequencies of sound in architecture and vehicles like motorcycles. This is sometimes also called a bass trap. One of the weirdest Helmholtz resonator stories I found is one that claimed the head of a Chihuahua formed a resonator.

Since many of the historical resonators were made of glass, I became interested in creating a series of fanciful Helmholtz resonators as a way to connect the well-established glass blowing art and industry in this area of Vermont to the soundscape. Simon Pearce is the largest glass manufacturer here, but I also discovered many incredible small glass blowing studios.

Michael Egan and Topher Kerr-Ayers

To fabricate these fanciful resonators, I was lucky to find and work with Granville-based glass artist Michael Egan and his talented right-hand man Topher Kerr-Ayers. In my opinion Michael is the most skilled and creative glassblower in this area, and a great pleasure to work with. In two days, we designed and created over 10 resonators of various shapes and sizes!

Topher at the Glory Hole

Placing what we decided to call a ‘blobe’ (pronounced like ‘globe’ meaning a blown blob of glass) on the top of a resonator in progress.

Design sketches

Some completed resonators (or ‘sound vessels’)

We will be hanging these vessels along the trails at the MBR park for a reception on July 15th from 3-6PM, then they will be placed in an installation in the Pony Barn.