Welcome all. Many of you already know about the Sweetwater Communications Group (some of you have even been our customers). To others, the Communications Group may be something new. This column is designed to familarize you with who we are and what we do — most specifically, what we can do for you! This forum will be used to discuss “system” issues (acoustical, electrical, electronic, etc.) in relationship to new design, renovation, and upgrading of existing facilities.
But you may ask what the Communications Group does. Well, in essence, the Group designs spaces — literally from the ground up — used for performing arts, sports and worship, as well as the systems that go into them (Pro Sound, Recording, Voice / Video / Data) to provide true integrated communications functionality.
Some of the topics I will be covering in upcoming issues include: Basic acoustics including sound isolation and absorption coefficients, AC technical, grounding, surge protection for electronic devices, sound coverage (for live PA), equipment interconnections, sound pressure levels, ADA and OSHA requirements, real world live speaker applications (and misapplications), AC power requirements for amplifiers, engineering standards, rigging, stage lighting, proper system installation methods and unique project profiles and solutions. Hmm, that should keep us busy well into the Millennium. Please note that if you have other topics relating to sound, communications and acoustics for live sound or recording that you would like to see discussed here, we can address those as well.
As an acoustical consultant with over ten years of in-the- field design experience, I will be providing informational “Factoids” which may appear to be somewhat obscure but are actually important information. I will also provide real answers to many questions, separating the “specmanship” from reality.
The first Factoid relates to the Sound Transmission Loss (TL) of walls: Light-weight double walls provide good isolation. Here’s the scoop: When two lightweight walls are separated by an air gap, the transmission loss (TL) increases as the space of the wall increases, up to about 15cm. With sound absorptive material in between (rockwool is great — pink is pretty — sprayed Celbar TM is wonderful), the TL further increases with larger spacings. Note that an air gap is always beneficial, even with absorptive material in the cavity. Lightweight double stud walls can provide the same TL as single walls that are five to ten times as heavy (ie: masonry).
Here’s an example: A wall constructed of 13mm plasterboard on both sides and staggered studs in a 5cm cavity, will provide an average TL of 37dB. Increase the spacing of this same wall structure to 15cm and the average TL increases to 47dB. Add 30mm of insulation to one side of the wall assembly and the average TL increases to 55dB. Increasing the mass by using thicker plasterboard will increase the low frequency attenuation. Special note: Very low frequency (< 100Hz) attenuation requires a very thick wall assembly or one with very high mass.
Well, that should give you an example of what we will be discussing. As always, your input is welcomed. We want this column to be useful, providing real world solutions to common (or even not-so-common) problems. So please let us know if there is anything you’d like to see discussed in upcoming issues.