Greetings from all of us at Thorburn Associates and welcome to our August eNewsletter. We hope the summer is treating you well and you have been able to balance a little summer fun with a healthy workload.

The fall trade-show season is just around the corner, and we’re making our plans now. If you happen to be at any of these shows, please look us up and say hello.

• AIA North Carolina - Asheville, NC, September 15 - 17
• SATE -Orlando, FL, September 30 - October 2
• EDUCAUSE - Anaheim, CA, October 12 - 15
• AIA South Carolina - Hilton Head Island, SC, October 21-24
• ArchEX East - Richmond, VA, November 3-5

As always, it is our goal to make sure that Thorburn Associates is your single point of contact for all your Technology and Acoustical Design services. If you have an idea, question, or suggestions, please drop us a note at enews@ta-inc.com.

When we work on a project to mitigate the impact of an environmental noise source (such as a nearby highway or outdoor cooling tower) on a residence or outside use space (such as a playground), someone always asks about putting in a line of trees or shrubs to lessen the offending noise. While there is a very real psycho-acoustical phenomenon that takes place when a sound source is no longer visible, the reality is trees and other plants do little to create sound buffers.

There are many factors that affect how noise travels over distance, such as wind speed and direction, temperature and humidity. However, as a rule of thumb, a sound is reduced by about 21 dB over an open distance of 100 feet. That is if there is an open area of 100 feet between a noise source and a listener the noise will be approximately 21 dB quieter than if the listener were directly adjacent to the noise source.

One would think that a forest of trees or shrubs would help to reduce even more of that sound. However, trees and shrubs do not reflect or diffuse sound like massive and rigid noise barriers do. Instead, they absorb some of that sound energy, and therefore the denser the tree and its foliage is, the more energy will be absorbed.

Consider sound the same as a wave on the ocean approaching a marina. A solid pier or breakwater reflects that wave back into the ocean, leaving areas behind it undisturbed. But a more porous barrier, such as a line of rocks, will only provide partial protection as it breaks up that wave and absorbs some of the wave’s energy. But some of that wave’s energy will still disturb the calm marina water. Trees and foliage act the same way.

Deciduous trees (ones that seasonally lose their leaves) have a greater area between leaves and are less dense, therefore providing a greater space for the sound energy to travel around the object. However, when deciduous trees lose their leaves every autumn, they lose nearly all beneficial noise reducing properties. Conifers (like pine trees) on the other hand, are quite dense in comparison and will trap the sound energy year round. Shrubs and other plants act in the same way as trees; the greater the density, the greater the reduction in decibels they will provide.

Still, the decibels saved might not be worth the effort. On average, 100 feet of dense pine trees will only provide an additional 5 dB of noise reduction. So while there is a helpful advantage to such natural barriers, it often requires a lot of real estate for it to be an effective solution.

Designing presentation facilities can be challenging, but the basic principles are not difficult. Each project and venue comes with its own set of variables and limitations that require some analysis to determine how to create the most optimal conditions.

The key visual element in a presentation facility is the screen. The size of the screen is tied to the size of the room, and changes to one can affect the other. In order to understand how the two are related, it’s important to understand some of the standard ratios involved in the creation of a facility.

The 468 Rule is the basic concept in determining image size in a presentation space. It sets the image size based on the furthest viewer from the image. The image height in a room should be at least 1/4, 1/6, or 1/8 the distance to the furthest viewer, depending on the type of content being viewed.

For example, in a facility where the furthest row of seats are set at 72 feet from the presentation / front wall, a screen being used primarily for general video content should be 1/8 that distance, or 9 feet tall. Detailed viewing requires 1/6 the distance, or 12 feet. Inspection viewing needs 1/4 the distance - in this case, a screen that is 18 feet tall.

Once the image height is determined the width is set by the aspect ratio of the image content. 4:3(1.33) is a traditional computer display but it is becoming more common for content to be provided in a widescreen format such as 16:9(1.78) or 16:10(1.6). By taking these fixed ratios of the projected content and multiplying by the image height the image width is determined. In the example of a 9-foot tall screen, a standard ratio (4:3) would suggest a 12 foot wide screen (4 x 9 = 36, 36 / 3 = 12). A widescreen ratio of 16:9 would suggest a 16-foot wide screen.

Of course the first compromises often start here. Usually the theoretical image size won’t fit a “standard” screen size from one of the projection screen manufacturers so there has to be an adjustment. Manufacturers do make custom size screens but it costs more and takes longer for delivery, so a “standard” size is often preferable if it does not seriously compromise a project.

Now that the properly sized screen has been found as the best fit for the space, it’s time to focus on where to position the screen in relation to the seats. In the next newsletter we will explore the angles and standards used in creating optimal presentation facility viewing.

The North Carolina Central University (NCCU) Pearson Cafeteria Renovation and Expansion project includes a modern cafeteria with a seating capacity of 1,750 students, dining facilities for staff and various conference rooms. Since the project’s inception in 2003, the project budget grew from $1.3 million to $13 million while the square footage increased from 27,000 sq. ft. to 56,000 sq. ft.

The facility also includes a special Teaching Kitchen. The Project Requirements called for a space designed for classes on cooking and food preparation where a chef/instructor could move freely from one food preparation station to the next and still allow the students to see and hear what was going on from their desks. Additionally, each food preparation station needed to be recorded on video and/or transmitted over a video conferencing system for distance learning.

For incoming distance learning video, a wall mounted flat panel display is located on the central column facing the student seating area. Two motorized video projection screens roll down at the front of the class to the left and right sides of the food prep stations for viewing the lesson/meal in progress.

The following cameras are necessary to cover all of the areas, all controlled remotely. A wall-mounted camera is located on the back wall for a view of the instructor. Ceiling mounted cameras over the food prep tables look down on preparation surfaces for a bird’s eye view. Behind the food prep tables are the various hot cooking surfaces, fryers and soup kettle. Remote cameras are also located under the vent hood over the “hot” preparation area. These cameras are mounted in an air-tight protective housing behind a glass dome in order to keep hot steam and grease from compromising the camera optics and electronics. The instructor chooses which camera feed to display by way of a remote control panel or a push button located near each camera.

A wireless head-worn microphone, kept less than an inch from the instructor’s mouth, picks up their voice. This type of microphone was chosen because of the high level of fan noise coming from the fan hood.

The completed kitchen allows the chef / instructor to teach a large number of students both in the classroom and at distance learning centers.

The latest short-focus projector from Sanyo (PLC-WL2500) combines the limited maintenance features of their traditional models with the benefits of a short-focus projector. An 80-inch wide projection is possible with a mounting position only 34 inches from the screen. This allows the projector to be placed on a desk or be mounted on the ceiling without fear of shining in the presenter’s eyes.

While other models (such as the PLC-XL51) project an 80-inch image from a distance of 3 inches, (yes inches) the PLC-WL2500 benefits from an average 4,000 hour bulb and filter lifespan, requiring less maintenance. The projector also boasts an output of 2,500 lumens and a 10-watt loudspeaker.