ESOTERICA

"Designed for and understood by the specially initiated."

Lurking in the mind of all experienced audio-visual types are arcane pieces of information that while important at one moment in time, are generally not worth repeating.

Nevertheless, Gault & Associates, Inc. believes that this esoteric information may convince you we know what we are talking about. Thus we have complied a listing of such minutiae and present it here from your review.

What are the most used tools to deliver presentations?

Overhead projector
Prepared flip chart
Multimedia projector-data display device
35mm slide projector
Internet
Plasma display
Other

Survey results are from 3M's online survey. Full results are available from the 3M Meeting Network site.

What is the optimum distance between the monitor display and the farthest viewer?

It should be no more than 8 times the height of the viewable image. Example: A 27 inch TV with a normal aspect ratio has a display height of 16.2 inches. The monitor should be viewed by no one more than 10.8 feet away.

MONITOR VIEWING DISTANCE CALCULATOR
Enter the monitor display height in inches, then press the CALCULATE button:

Maximum Viewing Distance:	FEET

What size screen should I use?

Remember the 2 and 6 rule-
Screen width should equal and not exceed one-half the distance from the screen to the first row of seats. Screen width should equal or exceed the distance from the screen to the last row of seats divided by six. If a difference exists between the two guidelines, the one with the larger screen width should be used. For multi-image projection, double or triple the width, according to the number of side-by-side images.

Can you explain how the throw-to-width ratio works?

But of course. There is a direct relationship between the screen Width and the Throw distance required to achieve it, for a specific projector aperture and lens focal length. Once you know that relationship, you know everything you need to about the lens in order to calculate screen width/throw distance. That relationship is expressed as a ratio.

How do I use this great information?

It's a factor. Just multiply the known Width number by the factor to get the previously unknown Throw number. Example: If there Throw to Width ratio of a lens is 1.22 then a 10' wide image requires a 10' x 1.22=12.2 Throw to achieve it.

But what do I do if I need to calculate the screen Width and you know the Throw distance?

Just multipy the known Width number by the factor to get the previously unknown Throw number. That would be a Width to Throw ratio. Divide "1" by the Throw to Width ratio, and you have it as a factor.

Example: If the Throw to Width Ratio is 1.22 then the Width to Throw ratio is 1/1.22, so a 12.2' throw will result in a (1/1.22) x 12.2'= 10' wide image. Got it?

How do I find my computer's native resolution?

On a PC, go to the Control Panel, open the display folder, then click on the Settings tab. In the lower right third of the window the Desktop Area will be shown. Unless the last user adjusted it, it will show the native resolution. All laptops are now being shipped with XGA (1024 x 768) desktops or higher.

I want to play a CD on my laptop while my PowerPoint presentation is showing. I own the CD. Is this a violation of copyright law?

YES!

I want use a Dilbert cartoon that I've made into an overhead transparency during a presentation. Is this a violation of copyright law?

YES!

How long does copyright protection last?

It lasts for the lifetime of the creator, plus 70 years. Then it passes into public domain free to be used without permission. BUT there's a catch. An individual performance of, for example, Bach's music by a contemporary group is a different thing. That performance can be copyrighted and you'll need permission to play it.

I've read that all microphones aren't alike in the way they pick up sounds, but I don't know the differences. Can you clue me in?

There are OMNI DIRECTIONAL microphones, which pick up sound equally from ALL directions. This can be helpful to pick voices from several directions. This can be bad because it may pick up undesired background noises as well as greater amounts of room reverberation. This can produce a hollow, "inside a barrel" sound. But worst of all they tend to produce feedback easily.

There are UNIDIRECTIONAL microphones, which reject sound coming from behind the microphone while still picking up sound from the front. This helps reduce feedback and room reverberation. The most common of this type is the cardioid, so named because its polar pattern resembles a heart-shaped figure. Supercardioid and hyper-cardioid reject progressively more sound from the sides and pick up more sound from the rear.

Sometimes the wireless microphones I use work, sometimes they don't. Will you explain?

Such microphones are like small radio stations as they operate on specific frequencies regulated by the Federal Communications Commission (FCC). There are four (4) different sections of the frequency band:

Low-Band VHF (49-72 MHz)-Used by radio-controlled toys, cordless telephones, baby room monitors and other consumer products. Interference as you might imagine is likely to be picked up.

High-Band VHF-This is the most widely used for professional applications and quality systems. It shares the airways with VHF television stations (channel 7-13), so it is important to know what stations are in the area where the system will be used. We can tell you what channels should be used in what area. Generally if you are traveling, you should choose one of the so-called "traveling" frequencies. These are frequencies in the 169-172 MHz range that are just below channel 7 and not subject to interference. However in areas with navigation buoys or hydroelectric equipment (dams), these may interfere with your system.

Low-Band UHF (450-614 MHz) and High-Band UHF (806-952 MHz) Are becoming popular as congestion in the VHF band increases. UHF is much less crowded, but the equipment costs more to manufacture. Prices are coming down however, as manufacturers respond to the need for using these less clogged airway increases.

Once you decided on the frequency, you need to decide which type of receiver you need to use: single antenna or diversity.

The first type (guess what) uses a single antenna to receive the signal from the body-pack or handheld transmitter. This broadcast signal is radiated in all directions at the same time and is reflected off floors, walls, ceilings, etc. until it reaches the antenna. If two reflected signals reach the receiver at the same time, no sound is heard. This is called a "dropout".

Diversity receivers are much better with their two antennas. The strongest signal received is selected by the receiver and used. It is very unlikely that both antennas will be interrupted at the same moment. Gault & Associates, Inc. uses only diversity systems and you should as well.

When using wireless microphones, keep the distance from the transmitter to receiver under 100 feet, closer if the signal must travel around corners or through doorways). With belt-pack transmitters, make sure the antenna cable is hanging straight. If it's coiled up in a pocket, it transmission distance is much shorter than normal.

Two ground rules ALWAYS apply:

Always place the microphone as close as is practical to the sound source. Every time the source-to-mic distance increases by a factor of two, the sound pressure level reaching the mic decreases by a factor of four, making clear sound pickup progressively more difficult.

Use the lowest number of microphones necessary for the situation. Sometimes there is a tendency to "over-mike" a setting. Excess microphones mean more background noise pickup, greater chance of feedback and more levels for the operator to keep track of.