Study Hall

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Whistle While You Work: Using Your Body As An Ultra-Low-Tech Test & Measurement Instrument

A guide to your "on-board kit" and how it can make your work a little quicker and easier...

One Step At A Time

Do you know the length of your stride? Between two and a half and three feet (30 to 36 inches) is common for most adults. It’s a good idea to learn your stride length so you can walk off a room’s dimensions, or the distance between the mains and delay loudspeakers, with some reasonable accuracy.

There’s little you can do to cross check your delay-finder results if you don’t have a reasonably quick way to measure the distance between two loudspeakers. If you have a delay loudspeaker that’s 50 feet from the mains, know that the delay setting must fall somewhere around 50 milliseconds (ms).

Yes, I realize 50 ms doesn’t translate perfectly to 50 feet, but that’s not the point. The point is that if the loudspeakers are 50 feet apart, and the delay-finder shows you 150 ms, or 15 ms, it’s important to quickly be able to recognize there is a problem.

Tip To Tip

Do you know your wing span? Just like your stride distance, it’s another measurement tool that goes everywhere with you. My tip-to-tip wing span is almost exactly 6 feet, and when not wearing shoes, I can stand flat footed and just brush an 8-foot ceiling when my middle finger is fully extended.

Knowing these two dimensions allows me to estimate a variety of dimensional variables. Examples: What is the ceiling height in the room? What is the height or width of a door opening?

Estimating ceiling height becomes fairly easy too. If it’s an 8-foot ceiling, I can tell in a second or two. If it’s a little more or less, that becomes instantly obvious. Do I need more detail for a final design? Of course, but on day one, I know what ballpark I’m working in.

For a door’s height, it’s pretty much the same as reaching up to touch the ceiling. A common 7-foot door opening falls about 4 inches below my wrist. For door width, the tip of my nose to the tip of my middle finger is 36 inches. A double-wide door is often 6 feet in width. Again, I don’t need these numbers to be perfect – I need to know if more exact measurements are needed before proceeding with something that has a significant impact on time and money.

Example: As a former integration designer, sales engineer and estimator, it was common to call out the appropriate scissor or boom lift(s) to help with an install. On the initial job walk, I could estimate room size, ceiling height, door size, and floor access in just a couple of minutes.

If everything lined up, based on my knowledge of available lifts and their most compact and extended dimensions, I could move on with confidence. If not, I could make a note for the project manager to verify sizes and dims before budgeting or calling a lift on site.

For ceilings that are well above 8 feet, it’s a little more involved, but not much. The trick is to use proportional scaling. Here’s how: If you know your vertical reach, find a place on the wall that matches your reach. It can be anything physical that you can easily see from a distance. If necessary, even a sticky note or a piece of blue painters tape will work.

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Now, step far enough away from your wall mark that the space between the floor and your mark shrinks down to match the width of your hand (all fingers touching), when your arm is fully extended in front of you. Turn your hand sideways so your fingers are parallel with the floor (Figure 1). Just use four fingers, your thumb is not needed.

Figure 1: Proportional scaling using your hands and a known vertical dimension on the wall.

When the outside edge of your index and little fingers match the vertical distance between the floor and the mark on the wall, you’re standing in the right place. Now, simply place the edge of one hand above the other and count how many hands it takes to reach the ceiling. If you’re using an 8-foot scale, four full hand widths will equal approximately 32 feet. Further, each finger also represents about 2 feet. If you can’t get far enough away from the wall use something larger than your hand, like a book or a sheet of printer paper.

To finish the list of body-as-a-tape-measure tips, I offer the following:

1) How wide is you hand from the tip of your thumb to the tip of your little finger when your fingers are spread out as much as possible? (Mine is 9 inches.)
2) What’s the distance between your index- and pinky-finger tips? (Mine is 6 inches.)
3) What’s the distance from the floor to the top of your kneecap or navel? (Mine are 24 and 42 inches, respectively.)
I’m sure with a little effort and investigation you’ll find many ways to take advantage of these simple, dimensional properties, that you carry around every day.

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