Category: Entertainment Technology

Catchall Category

4c – Audio (Sound Basics): Part 3

Hi again. This is a work-in-progress…do not read yet.

At the very end of Audio (Sound Basics), Part 2 we introduced the concept of Frequency when discussing waves. We also mentioned some basic information about the speakers in the room, which create the waves that we eventually hear. This article will build from there. You can skip all of this and you can still talk to a technician, but it is really simple. It just looks long because there are a lot of examples.<!–more–>

It was said that we can think of sound like the waves made by a falling pebble on the surface of a pond. This isn’t exactly true, but that is the trouble with analogies – they are similar by not exact. At least you can see a wave in water. A sound wave, not so much. So, we’ll proceed with this analogy as far as we can and explain the difference later. Because we have to learn about sound, and sound is made of waves that are created by the speakers.

So, the experiment is dropping a marble in a pond from the same height each time. If we look closely at the expanding waves, we will notice that the first wave is always taller. As the wave moves away from the source point it gets shorter and shorter. But, while we can see it, the distance from the peak of one wave to the peak of the next stays the same.

What we are seeing is that the power is getting distributed around the water in the circle, so the height goes down. But while it was happening, the number of waves going past the place you were looking at was constant. If we could look while also measuring time, we would notice that the number of waves that go past in the first 5 seconds is the same number of waves that go past in the next 5 seconds.

The distance between the peaks of the waves is called the Wavelength. The number of waves every minute or waves per second is called the Frequency. These two are completely related – as the number of one goes higher, the number of the other goes lower. The higher the Frequency – that is, the number of waves going past per second or minute – the shorter the peak-to-peak Wavelength. And, the opposite; the lower the frequency, the wave length is longer.

An easier example of these opposites is waves at the beach. If we see them crashing to the shore at 15 a minute, we can probably look into the distance and see several waves coming in. (High frequency, short wavelength.) But if you see the surfer who has to stand on her board to see the next wave – that is, the peaks are very distant, that means they have a long wavelength, and sure enough, there is a low frequency – you will see that there are only a few waves per minute crashing on the shore.

You can almost see this with a piano or guitar or harp string. When the low note is hit or picked, the string travels back and forth so slowly that you can practically see it (although, no matter how fast I can count, I can’t keep up.) But the actual sound wave that it is generating is very long. For example, the low note on the piano moves back and forth 27.5 times every second – we say 27.5 cycles per second. The wavelength – and you’ll just have to believe the science people on this – is over 10 meters long…over 33 feet!

And, here is the important part – you can pound on that note hard or soft, but the frequency of the strings and the sound will be the same…and the wavelength will be the same! And the same is true of a high frequency note, which might have a wavelength of only 6 inches (.15 meter), and a frequency of 2,500 cycles per second.

So, let’d end Part 2 here. Just one more silly thing.

Mr. and Mr. Hertz raised a very clever son who figured out that the theories of a very clever guy from Scotland named Maxwell were probable. The theories were about electricity and magnetism in a time when they were both considered spooky actions at a distance. It was a classic example of what Issac Asimov meant when he said “Any sufficiently advanced technology is indistinguishable from magic.” Anyway, his work was all about understanding waves and you will hear (or read) “cycles per second” called Hertz (abbreviated ‘Hz’), or kilohertz (kHz is the formal abbreviation, but the slang abbreviation is just ‘k’ – so you’ll hear, “The explosion had no sound above 1k”, meaning, there were no high frequencies above 1,000 Hz (kilo- means ‘thousand’)

Next we will tie these all together, add a little power and figure out what these terms have to do with your auditorium.

 

 

 


If we hit a bell with a hammer, it goes ‘bong’ or rings with a high pitch, depending on how it was made. If we feel the bell while it rings we can feel it vibrating back and forth just like the guitar string.

 

In and out, not up and down.

The height of is not the frequency of the wave. The height shows the power of the wave – the force of the energy that is expanding outward from the source point. The frequency is the number of waves that go by a certain point in a particular length of time. The frequency can be the same even if the waves are taller or shortLike the piano strings or a guitar string being struck, we measure sound in wave cycles per second. In this case it is like the water wave, a cycle is measured from the when that top of a wave passes a point until the next top of the wave. If our eyes were able to see the string move as it goes back and forth, it would be a complete cycle from left to right to left again.

When we talk about sound waves, we talk about power as intensity or volume – how loud something is. And that is where we start talking about the son of Mr. and Mrs. Bell.

Basics: Audio (Sound). It is good to have a basic understanding of frequencies and speakers and surround and amplifiers and level and Loudness.

Frequency is a term used when describing both sound and light, so we will need to get a good idea of it. Sound frequencies are very easy to think of when we consider a musical instrument like the piano. From left to right, the notes start with bass and

There are two reasons for this: power and clarity.

Power is simple. The auditorium is large and the sound must get to all of the audience without being too soft for some and without being too loud for others.

The Other-Abled, and You

There’s a funny thing on the internet that lets people in public service jobs know how to deal with those who are disabled – those poor disabled people who have no ability to use Braille or sign language in this case!

What to Do when You Meet a Sighted Person

Sighted people tend to be very proud and will not ask directly for assistance. Be gentle, yet firm.”

Calmly alert the sighted person to his or her surroundings by speaking slowly, in a normal tone of voice. There is no need to raise your voice when addressing a sighted person.”

OK;  jokes aside. We are in a service business, and we get a lot of practice dealing with people who can walk strait to the proper line without assistance, but we don’t get a lot of practice dealing with people who need different kinds of assistance.

Does that blind person get a benefit from using Closed Caption equipment? Uhm…probably not. Audio Description equipment? Yes! Probably, yes. Should you ask? Good idea.  Continue reading “The Other-Abled, and You”

DCP TIFFs

Intention: Provide materials which can help a technical or non-technical person judge changes in picture and sound quality without the use of meters.

That phrase means what it says – if the test equipment isn’t scheduled for the auditorium for another 6 months, is there a way to tell if the the contrast and color display is degrading. These TIFF slides are experiements to answer this question, and supply tools if it is possible.

All these TIFF plates are 4096 x 2160, 2020 color space with 16 bits of depthiness, unless otherwise mentioned. Sound files from the DCPs will get their own page, but don’t go looking for it now…

If you have some ideas for changes, to fix mistakes or add nuance, let us know…likely we can change the master for the better or post another version. Creative Commons License
This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.
If you create something and would like it hosted on this site, please let us know. Read what the link says on the Creative Commons site. Generally, use them in your works, change as required. But please, 1) give attribution when use them either in commercial or non-commercial work, 2) provide a link to the original material and, 3) send a note to let us know what you changed.

Primary and Secondary Square Cones

Striking, and only useful if you are looking for striking. But a lot of time was spent on it, so only say nice things, please.

conical gradients Blk to white primaries and secondaries

 


Primary and Secondary Trumpets

Each of these components will be made available in a kit, but for right now, here they are I one chart.

LensTesting for DCinema!

 


Mach Band Effect Testing Plates

There is a whole series to download here. These were developed to learn whether the black of the masking curtains and the typical vignette of the picture cause the illusion of luminance shift.
Variation 1 on Mach Band Effect Testing

 


Horizontal and Vertical Lines – Black, against backgrounds, 2020, 4K

Black lines at every other position on the grid…and a variety of different primary and secondary backgrounds.

Black lines against primary and secondary backgrounds 2020 16 bit

 


Horizontal and Vertical Lines – Colored Lines, 2020, 4K

What is the difference to a projector or a LED wall between drawn black lines and backgrounds of colors…which actually fill in the alternate lines, right? …and drawing the colors as the lines and letting the editing program put in the background…or no background at all. You too can find out with these plates.

colored lines, horizontal and vertical

 


Color Plates, 2020, 4K

Primary and secondary color plates – Don’t need pictures of those here, do you? Just get them at the download site.

 


2 Percent

Hmmm – What shall we call this? It is derived from the CST chart that marks off 2% rectangles to begin with, and a bunch of circles drawn at the proper 10% points…then it got botched up with moving the color wheels to align with the corner to corner lines which actually serve no purpose…ok, toss in some focus squares …that’ll distract them. (This png is 709…get the real thing in 2020 and tell us how to make it better please.

Colors on a black background that also checks the sides in a colorful manner.

 


2 Percent, Black and White

Hmmm – What shall we call this? It was inspired by/is derived from, the CST chart that marks off 2% rectangles to begin with, and a bunch of circles drawn at the proper 10% points…then it got botched up with moving the color wheels to align with the corner to corner lines which actually serve no purpose…ok, toss in some focus squares …that’ll distract them. (This png is 709…get the real thing in 2020 and tell us how to make it better please.

Black and white Siemens Stars with several 2% rectangles.

 


CJ’s Favorite Distraction

Several variations with several colors going from full saturation to dark or white …and grey level tests too. A distraction because I keep refining it. Now with MTF marks – hope they work…haven’t tested them yet.

Black background with sharp lines and green cones
Green Cones with MTF lines and other designs

 


Vertical Meters 2.5 and 5% RGBGrey
This mission, if you choose to accept it, deals with “Where does the color end and only black exist?” Is 5% a usable meters for each color or is 2.5% needed for the brighter ones? The theory is that one can look at the meter and make a substantially objective judgement, record it on one of the checklists, and use the test again a week or month later to note if there are changes. (Wow! This PNG only begins to show a usable scale…download the TIFF file.)

Vertical meter of each primary color and black at 2 different luminance.

 


Dials for Contrast: 6%, 4.5%, 3%, 1.5% RGB and Greys, with and without tic marks.

This idea is similar, but with the gradient from 6% to 0% (as well as 4.5% and 3% and 1.5% to 0) on a dial. There is a version with a set of tic marks to note where the last point of seeable color is…and a version without. Why? Because it may be that one needs to spot the postition without the influence of the dial markings, then get the markings later. Experiment and report please.

RGB and Greys. 2020. 4K and 16 bits of depth for each color. All to see if we can get a subjective objective.

A dial with tic marks to find contrast...in this case, green

 


Trumpets

8 TIFFs of Trumpets. The ability to watch as lines get closer together. There are many variations…there are numbers in there somewhere. Experiment and report please.

RGB and Black. 2020. 4K and 16 bits of depth for each color. All to see if we can get a subjective objective.

trumpets on a scope screen

 


Circles and Stars

Circles and Stars and a few other things to stare at. And some fun while making the primaries turn into secondaries. Ya gotta love bluey yellow, no? The alternative TIFF uses outlines of the Siemens Stars for the center position, just to see what detail they hold. No idea if a 4K system can hold 48 spokes…let us know what you find please.

RGB and Black. 2020. 4K and 16 bits of depth for each color.

A number of testing ideas on one chart

 


Coming….Colors, Stripes, Dials, MoreMTF –
A crafted circle in a triangle in a rectangle with 3 primary colors all around

Monday CleanUp

Do this to make sure things don’t get out of hand…

Monday Clean Up – 15 Minutes

Grab the dusting feather thing, and while you make certain that nothing is on top of any rack or projector, give a quick pass to keep the dust down.

Don't clean the port glass, but note down which ones are dirty.

The same with the lenses – should a task force be sent to clean them or the 3D equipment?

Dust on the port window and lens can cut down the light level on the screen by 10%. Wasted electricity, and sad customers.

I did these things. I dusted and noted what areas need more attention.
Things that need attention