Since there are many goals and purposes for this project, there are many things that need to be done.
Fortunately, they don’t all have to be done at the same time.
So, if you don’t have the organizational support to download DCPs onto a USB drive and load them into the Media Player/Projector system, you can still download some audio and light measuring tools, and experiment with them until you can use them easily in a dark room.
Audio Tools for the iPhone – There are many…manymanymany, in fact. Some are extremely significant professional tools at great cost – not knocking them, since they are reasonable if you are a pro who needs the complexity. Some are too simple or have pop-ups that will annoy you in the dark room. Some have the tool that needs several keypunches to get through to, yet another annoyance. I use two that are free, and quick and simple to get good data from.
What we need is something that quickly tells us 2 numbers. The first number is called Peak, which measures the sharp blast of energy that a clap of lightning or a single hand clap might have. The other is more averaging of all the sounds for a window of time…a moving window of time, in fact. (The name goes by the abbreviation of “RMS”, which stands for a technical term that sounds like a rapper’s name: Root Mean Square. If you are thinking it sounds like math and must be ignored, you are right!)
Many of the tools will have a Peak and RMS number displayed quickly and at the same time. This is what you want.
Let’s look at a few of these for the iPhone and iPad. If you find one that you like, especially for a different tool, let me know what you think in the Comments. It may be added to this evolving article.
An app that I keep coming back to is from dspmobile.com, named dB Volume. A very simple interface gives all the details you need. We’ll talk about the choices in the Lesson on Audio (soon to be posted.) But generally, high and low pitched tones need to be measured in a different way to get a usable response. That is why there is slow and fast response and different weight choices.
Ultimate Ears has a free simple tool as well, simply called UE SPL. The weighting is behind the ‘i’ button, making it a little more complicated to use, but it is nice to see a bouncing needle of what is called a VU meter.
Either of these work fine for what we need. These may or may not be perfectly exact, but we don’t care. Unless your iPhone gets thrown into a pizza, making the microphone read differently than the days before, it will give a consistent reading. Which means that we can measure the speakers consistently, and tell if there is something very different from day to day. When the sounds come from speakers, we can see their levels, mark them down and compare the results from last week and last month…all the way back to the time when the room was set up by a technician.
This is our only goal. Finding differences. It does no good to tell a tech, “Hey, it’s only 80 dB in the room.” There is no reference~! But it does good to say, “The left surround was 85 dB last week and is only 80 dB this week.”
The same goes for light and color levels, but they are not as easy to measure as sound. We’ll look at those tools in another article: Do This First…An Evolving Story – Light and Color