Training for Non-Technical Cinema Employees

Audio (Sound Basics): Part 2

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

  1. Become aware of sounds in the background,
  2. Become aware of differences in the many kinds of sounds around us.
  3. To figure out what sounds are annoying to you, and try to figure out the “why”.

Every good speaker designer has to learn these things. 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 off ceilings and walls (and people!), they will have taken classes in physics and design, and study angles. They may have experience with which magnets are the best to use in different speakers for certain frequencies – all that science stuff. And, they also need to know the things that artists know. How to observe.

How to decide what is pleasant, what is disturbing. Because: Acoustics, designing rooms for sound, is a science, but very importantly, it is also an art.

What we have discovered is that someone 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 through the system and into the room, they often 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. You don’t need to know the special wire that connects the speakers to the amplifiers in the best system. You don’t need to know the technical details about the media player and the audio processor. 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. And mostly, you need to be aware of sound …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 of the planet 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”. Musicians use beats, of course. But when we talk about sound science, and when we talk about light science and color science, we talk about cycles – and cycles per second.

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! The technical term is wave length.

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.

It is always opposite – high frequency notes have tiny little wave lengths. And low frequency notes can have wave lengths as big as the room.

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 see 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 piano 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 one of the speakers in the the Low Frequency Effects unit is cracked. 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.

And, as a matter of fun, play with the tools on this site:

Chrome Music Lab Experiments

In particular, spend some time learning relationships of ‘seeing’ sound at:

Chrome Music Lab – Spectrum

That’s a lot to do; don’t come back to re-read this Part 2 or start on Part 3 for a few days. Really, notice things with sounds, play with it – have fun. And let us know what you dug into in the Comments please.

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

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