Category: Sound Quality

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.

What Means, New SMPTE Pink Noise…and How?

SMPTE ST-2095-1 is a new standard for Pink Noise. It took a great deal of work by a great number of clever people, a lot of listening and testing and tweaking. The cool thing is that it isn’t made with a lot of transiticators, but rather, with digits. This is THE Digital Pink Noise Standard.

Pink Noise has been one of those things that has always been around, and people don’t think much about it. Flick a switch, and there it is. But it took a sophisticated circuit to do right, and it wasn’t always implemented the same…or even well. That is much less likely now because with the standard is a python script that is very easy to implement. Continue reading “What Means, New SMPTE Pink Noise…and How?”

6) Measuring – Sound

Since there are many goals and purposes for this project, there are many things that need to be done. Training is high on the list. Practice should be high on the list…but who has the time!?!?
Perhaps you don’t have the a friendly tech or projectionist to

  • download DCPs onto a USB drive and
  • load them into the Media Player/Projector system and
  • make a nice playlist,

You can still download some audio and light measuring tools, and experiment and practice with them until you can use them easily in a dark room.  Continue reading “6) Measuring – Sound”

4b – Audio (Sound Basics): Part 2

Before we took a break from Part 1 of Audio (Sound Basics), we had some tasks.

Become more aware of sounds in the background,
Become aware of differences in the many kinds of sounds around us. And finally,
figure out what sounds are annoying to you.

Every good speaker designer has to learn these things too. Every good designer of auditoriums need to learn these things. Why? Because sound all by itself is complicated, but to make sound go through speakers and reflect of ceilings and walls (and people!), they can take classes and study angles and which magnets are the best to use in different speakers – all that science stuff. And, they also need to know the things that artists know. How to observe. What is pleasant, what is disturbing. Because: Acoustics, designing rooms for sound, is a science, but very importantly, it is an art.

They can design a perfect room. They can set it up with the best equipment to have perfect balance. But when they play their favorite movie scene or recording, they often listen find things that are annoying.

You do not need to know about the 10 or 20 parts for each speaker, or the details about each speaker in each speaker box, or the special wire that connects the speakers to the amplifiers in the best system. You don’t need to know details about the media player and the audio processor and the every part of those.

Putting together all the parts is an art and a science for others.

You should be aware that these things exist. You should be aware that these things can have problems. But mostly, you need to be aware of…to learn how to… listen.


We will work on

1) listening to sound. And we will also learn how to,

2) listen to audience members, and

3) how to listen well enough to fill in the audio questions of the Managers Walk Through Form.


And now, our first real technical word: Frequency.

Frequency is a term that is used when describing both sound and picture. So we will need to get a good idea of it. Let’s do a quick once over to remove a little mystery out from the subject.

Think of a song. Think of the beat. . . . . . . . . . Count that beat for 15 seconds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .For this exercise we are going to use the number 30…30 beats every 15 seconds. That is 2 beats every second. If we counted for 30 seconds we would have 60 beats for every 30 seconds. And, for 60 seconds, 120 beats. 120 beats per minute. 2 beats per second. You can clap your hands that fast. Imagine the beat being 4 times faster…8 times every second…that may be faster than you can clap your hands.

Beats every second is a frequency. Beats every minute is a frequency too. Beats every day is a frequency, but the number may be too huge to count…and your hands would be pretty tired! But, the planet has made 1 revolution around its axis in one day…1 revolution every day is a frequency. And the planet earth will go around the sun in 365 days…1 every 365 is a frequency.

People usually say the word “per” instead of “every” when we talk about frequency. 1 revolution per 365 days. And sometimes we have to be careful – does that mean 1 revolution around the axis or 1 revolution around the sun? But with music…that is, with sound…and color…that is, with light…people understand that we are using seconds.

And, instead of beats we use the word “cycles”. Cycles are a little more fun.

When you clap, your hands go toward each other, then away from each other. They wave at each other going one distance out and then back in.

Waves are like that. They repeat their sequence. You can start counting the wave when the hands hit…the bottom of the cycle, or you can start counting the wave when your hands are farthest apart. Or start someplace in the middle. The important part is the cycle of the wave and the time. Cycles per Second. Cycles per Year. Cycles per Decade.

Cycles. Time. Frequencies.

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 the low and rumbling sounds and and go all the way up to the twinkling high notes. If you look at the longest strings of the piano as they are hit, you can almost see the back and forth slow motion vibration as they move through the air – and they act on the air – creating those low notes that hit our ears. If we look at the strings a few notes higher, they move so fast that we cannot see them vibrating.

The same is true for the guitar, which is easier to make a video of. Here is a video showing the strings moving in slow motion. Longer and shorter waves for each string…Cool! Longest waves for the bass, the low notes, the low frequencies. Shorter waves for the higher frequencies…but notice, there are more waves on the 3rd string than on the 1st string. Almost 4 waves on the 3rd in the same distance as 2 waves on the 1st. 4 waves per …something, compared to 2 waves per …something. Higher frequency, shorter wave length.

Hmmm…there is something here to study later…some reverse relationship between wave length and frequency. Let’s put that aside for later. It is just interesting, but not important right now.

So, a quick review. Frequency is the number of times that something happens, associated with a unit of time.

I saw my friend quite frequently…about once a week (for example.)

Once per second I am able to type a word…the frequency of my typing is one word per second.

The strings on the lowest note on the piano – the one on the far left – goes back and forth 27 and a half times every second. We say that it has a frequency of 27.5 cycles per second. Some of the notes in the middle of the piano go back and forth over 400 times per second – the ‘A’ note above middle ‘C’ is 440 cycles per second. The very highest strings vibrate at over 4,000 cycles per second.

Now. Why do we need to know about frequency?

Because customers will come to you and say, “The low frequency notes are buzzing.” And you can say, “Ah. Help me to understand more. Do you mean the low frequency, like the rumble of the explosions, or the low frequencies like the man’s voice?”

And your customer will think, “This person is interested and capable of getting this problem fixed – I’ll come back here!~”

Then you can tell the tech – “Yeah, like, the low frequency hits are causing some buzzing in auditorium 7. A customer told me, then I listened and it seemed like the LFE has a cracked speaker. It only breaks up on certain notes.”

The tech can now come into the auditorium with the right equipment, then find and repair the problem in a few minutes.

What was the alternative?

The customer says, “Hey. I’m watching Galaxy 9. Low Frequencies are busting up in auditorium 7.” Your new and uneducated employee falls asleep when the word “frequency” is used and forgets the customer even said an auditorium number. The tech gets a note that says, “Customer says sounds is messed up in one of the auditoriums that Galaxy 9 is playing in.” Tech comes in, has to play a bunch of stuff before hearing which sounds and what speakers are messed up. Spends more time going to get the speaker. Schedules a whole morning 3 days from now to get it fixed. Customers are unhappy.

Part 3 of Sound Basics will follow. But take a few days before you attack that. Listen to sounds again. Judge the difference between low and mid and high frequencies. Listen how most male voices are low, but not as low as many other low sounds. Be aware of your sensation of touch – how often you can feel low frequency tones on the arm of the chair for example.

Take a look at the Managers Walk Through Form. Notice the other sound questions. Get comfortable with the idea of listening for those things, at different places in the environment.

Sound Section of Managers Walk Through Form
Sound Section of Managers Walk Through Form

If you are really brave, dive into the Lesson: So Now You Want To Measure Sound. Go ahead. It is a good idea to get some physical experience instead of all these theory lessons every time. (Theory lessons per week…frequency.)

And, remember these two things: No one was born with this info. Everyone had to learn it, to experience it, to mess up, to learn again, to get better then mess something else up…don’t get discouraged.

And two, keep it fun. On this path are rocks and sand and dust and great distances between knowledge. Scientists still discover things about sound and hearing, just like they do with light and pictures and vision.

Don’t forget to write questions or thoughts in the Comments or in the Contact Form. Let us know what we could explain better, or didn’t explain at all.

Thanks…and until next time (Part 3 of Audio, Sound Basics ), keep a steady beat.

6) So Now You Want To Measure Sound Level

Hopefully you have read through the post named Basics: Audio (Sound), Part 1 and Part 2. It is good to have a basic understanding of frequencies and speakers and surround and amplifiers and level and Loudness. Hopefully you’ve noticed some of the many ways that the human hearing system has made things “interesting” in normal life, and while you have walked around your cinema theaters since learning more about these things. Continue reading “6) So Now You Want To Measure Sound Level”

4 – Audio (Sound Basics): Part 1

Sound is all around us. We don’t need any particular talent to use it. Doctors tell us that we can hear sounds in the womb.

Using sound well is a different story. Being able to judge sound, to know if it is the best possible for your clients – or at least acceptable – is another different story.

For a simple definition, “Sound” is what we hear. But actually every sound involves hundreds of steps. These steps begin with a motion that takes place at one point. We can’t see it, but you can visualize it by thinking about it like a pebble that is thrown into a pond.
Continue reading “4 – Audio (Sound Basics): Part 1”

9) What’s It Mean? Distortion??

Let’s do this again. We will go through a term that everybody uses but which has a different meaning depending on who you talk to. Which meaning do we care about? The meaning that will correctly get an idea across to the Tech Team. We must describe a problem so it can solved quickly and well.

Distortion – For our purpose, distortion is the term that describes the imperfect recreation of the original sound of the motion picture. There are other definitions and uses, including the use with picture details such as ‘brightness and contrast problems’ or ‘focus problems’ or different kinds of color and screen problems. Continue reading “9) What’s It Mean? Distortion??”

5) Artistic Intent…Protecting the Dream

Let’s go back to a very basic concept – the very idea behind “Why We Care” quality of the picture and quality of the sound that our customers experience.

Someone had an idea for a story to tell, and somehow that story met a producer and director who found the money to be able to tell that story as a movie. That is the intention – to tell the story to a bunch of people. Maybe, actually, to tell the story to a bunch of people in a room with a bunch of other people.

How this story gets told is sometimes called Artistic Intent. Because it is the Director who is hired to carry the vision and purpose forward, often this is called the Director’s Intent.

The Director and Producer hire the Cinematographer team. They are the people who can cleverly make a camera capture the light reflecting off the scenes and reflecting off the actors into the lenses. Audio people and many others are hired to capture the sounds and make the scenery and perform clever stunts. They hire Post Production teams to manipulate and edit and balance the sound and pictures. After much labor, a distribution group puts the finished movie onto hard disks or satellites. And after all that work, the finished product somehow gets it into the equipment of the cinema facility.


In a different Lesson, we explained how Engineering is the Art of Compromise. It is the same with movie creation. The Art of Compromise is everywhere. There is only so much time and money, the technology can only do so much, and eventually the release has to meet a delivery date.

After all that work, there it is, the final lens. Just in front of that little piece of glass in the back wall of the theater – the Port Window. The movie shines through them both, and into the room and onto the screen and through the speakers.

The Director’s Intent wasn’t to spend money for technique and tools at a clever production set or post-production room. The Director’s Intent wasn’t to keep a lot of people employed or to make the camera sales people happy. The Director’s Intent wasn’t to sell a lot of popcorn, even though all these things may happen and are important to a lot of people.

The Director’s Intent is to create an effect upon your mutual audience.

It your job is to help create that effect. You participate in the Artistic Intent by making certain that your tools are operating at the optimum level possible.


Of course, the bubble of the Art of Compromise also surrounds the cinema sound and picture projection equipment. It surrounds the auditoriums with their screens and seats. Movies want to be shown in a perfectly dark room, but safety requires that there are exit lights and illumination on the stairs and walkways. Movies want the screen and speakers to be perfect, but speaker parts get older and less flexible every day, and screens get a little darker. How often are they changed, or adjusted? Speakers and screens (and seats and air conditioning and, and, and…) all cost money, so they get replaced when they reach some compromise level…not perfect, not horrible.

Nobody ever says, “I think I am going to present ‘Horrible’ today.” The opposite, “I think I will present ‘Perfect’ today,” is not going to happen either. Perhaps the best description might be, “Appropriate Compromise.” I’ll project the best I can with what is available.

Who decides what “Appropriate” is? Some might say, it is the big boss of the cinema who balances the requirements and dreams and ability of the audience to pay. Some might say it is the audience who is the boss, who the big boss has to respond to, but most will agree that the audience can’t define perfect or acceptable. They expect us to be the experts, to know what to look and listen for. The audience just knows what is irritating. If you’re lucky, they may know how to describe a problem.

Either way, it is your responsibility to deliver the best you can with the assets and policies that the big boss has given you. Some might say “Deliver more than you promise”. What you certainly want to do is remember – You are part of the Artistic Intent.


The purpose of all these lessons is to help you find problems before the audience finds irritation. In addition, if an audience member does find a problem, who want to know enough so when they describe it to you, that you can understand it well enough to give good information to the tech who has to repair it.

And that is our job, to give you tools and information so you can do that easily and well. Let us know what we can do for you, so when that magic day arrives when a director or cinematographer or sound editor comes up to you and says, “Thanks, that was just right”, you know that you did something to make it that way.

Now, when someone asks what your job is, what do you say?

I help create a better experience of audience members.

I am the last person in the chain that delivers the Director’s Intent.

Maybe we need a t-shirt contest for this.

Where Artistic Intent Meets Your Life in the Cinema