# beginner looking for articles

#### miriam

##### Active Member
Hi all,
I am taking a course in sound but it is not in English. Do you know of any articles I can read to supplement the class, just so I can make sure I understand?
We just started, so it is properties of waves--
frequency, amplitude, velocity, wavelength, shape, phase, delay, harmonics, "envelope" (that's as close as I can get to an English translation. Attack, decay, sustain, release together make the "envelope"), and decibels.
Does anyone know of any articles on the above as they relate to the stage? Or any webites that have very beginner articles would also be helpful.
Thank you so much!
Miriam

#### icewolf08

##### CBMod
CB Mods
What language is the class in?

In any event, I would look into finding a copy of: The Physics of Sound (3rd Edition) by Richard E Berg and David G Stork. It is a fairly good beginners guide to sound in general. It covers everything you asked about and touches on how sound is created and travels, instruments, amplification, etc.

If you then want to get into more theatre related reading Sound Design in The Theatre by Dr. John Bracewell is a good book, but hard to find and expensive. I hear that Doc Bracewell is working on the second edition now that he has retired from teaching, but I am not sure what the timetable is for it's release.

You can also feel free to ask us, we love answering questions! Also, stop by the new members area and tell us a little about yourself. Welcome back to CB! (as i see you had one other post from last year)

#### Eboy87

##### Well-Known Member
Pick up a copy of the Yamaha Sound Reinforcement Handbook. There's a lot of good information in it about the basics. Also, check out the Study Hall over at Pro Sound Web. Study Hall More information for beginners.

#### miriam

##### Active Member
Thanks for the feedback. I am in Israel, so the course is in Hebrew. Some things are obvious, like amplitude is amplituda and harmonics is harmonica. But a wave is gal and frequency is teder. So I need to pay close attention.
English books on this subject are not found in the bookstores I have tried. Used bookstores sometimes have something useful, but their stock changes all the time. I will definitely hunt around, though, for the titles you mentioned. I hope to get to the point where I am designing the sound.
I looked up the study hall and it seems a fabulous resource, thank you!
I think the next class will be all about mics, so I may have more questions on that.

#### icewolf08

##### CBMod
CB Mods
If you have a hard time getting english books in Israel, I am sure there are people here (myself included) that could help get literature to you. I know that amazon carries The Physics of Sound and they ship international, so you can probably import that. Let us know.

Fight Leukemia

#### miriam

##### Active Member
Thank you for all the replies. I really appreciate it.

This is a bit off topic, but why do I care about the velocity of sound waves? In practise am I really going to be doing math problems?

#### derekleffew

##### Resident Curmudgeon
Senior Team
Well, if you have delay speakers, you're going to need to set a delay time, so that the sound from the mains and the delays arrive at the listener at approximately the same time. Otherwise there'll be an "echo" and intelligibility will suffer. To calculate how many milliseconds of delay is needed, you're going to need to know: a) the distance of the main speaker to the listener, b) the distance of the delay speaker to the listener, c) the speed of sound, d) the speed of electrons through wire [approx. the speed of light, and generally considered zero time, i.e. instantaneous, in audio calculations]. So the formula would be [noise boys, correct me if I am wrong, I'm a lighting guy]

[a-b]/[c(=1100 ft/sec)] = # of milliseconds delay time required.

Just one example of "why you need to care about the velocity of sound waves."

#### museav

##### CBMod
CB Mods
Departed Member
If you end up designing or laying out sound systems you will be doing a lot of math and the speed of sound (which varies with temperature and humidity) will be a major factor. Not just in delays as dereklefflew noted, but also in looking at how speakers interact, why you may be getting a null or a peak at a certain frequency (which may be due to in and out of phase reflections off a nearby surface), how to setup directional subwoofer arrays, etc. Even a basic system design often involves logarithms and trigonometry.

Rane has a very good list of books on their web site and NSCA (www.nsca.org) has a technical bookstore with several audio related books.

#### miriam

##### Active Member
Okay, so let's say I have a room 100 meters by 150 meters (I don't know the real measurements). There are ten collumns (I think). The stage/dressing rooms/proproom are usually built against one of the 100m walls. The audience goes to around 2/3 of the room, then we put up partitions.

What sorts of info do I need, and what sorts of info do I figure out, for me to have the best placement of everything (I mean for mics, speakers)?

Many times there are song/dance routines, sometimes drama, sometimes skits. Sometimes it is blistering hot, sometimes it's very cold and rainy. Very rarely is it freezing.

Thanks!

#### gafftaper

##### Senior Team
Senior Team
Fight Leukemia
I seem to have accidentally posted several answers to your original question about looking for articles and books in your new member thread. Also I tossed up a thought for Derek or anyone who's worked in a road house environment to expand on over there.

#### derekleffew

##### Resident Curmudgeon
Senior Team
Hopefully, you'll learn everything to answer your own questions later in the class, but for starters, you'll need to know:
1) The exact dimensions of the space
2) The height of the ceiling
3) The absorption/reflectance coefficient of every surface in the room: walls, floor, ceiling, seats, drapery, "partitions" as you call them, scenery, big fluffy costumes
4) The number of audience members [humans and their clothing absorb a lot of sound, thus a room always sounds better (looks better too!) with a full audience than when empty.]
5) The possible hanging positions of your speakers.
6) What the purpose of the sound system(s) is: speech reinforcement, orchestra reinforcement, sound effects, music playback, etc.

Once you know all of the above, it is possible to input all that data, as well as a CAD drawing of the space, into an audio modeling software program such as EASE™ (and there are many others) which will let you "demo" different speakers, quantities, and locations, to give you a pretty good idea about how the system will sound. Once you have decided where the speakers should be, then you can move to microphone selection: wired or wireless, stationary or worn by actor, etc. Cost for a sound system for a room 100m by 150m can range from $500US (2 speakers and one mic) to$100,000US (maybe even more if you have 20 of the best wireless mics at $3000 each, and a$50,000 digital console.) Obviously, your only limitation is budget.

The books and internet resources already listed will give you a good start, and every show you do in the space should sound better than the previous, as you experiment and learn more.

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#### miriam

##### Active Member
I think I have an issue with wanting to know everything, like yesterday. People here are so giving of themselves. Is that a trait specfic to technicians, do you think?

Why do things that absorb sound make the sound better? Is it because there are fewer waves bouncing back? There's a word for those waves, correct? The instructor calls them mukdamim.

I would have thought the bouncing waves after the initial sound would just make it that much more effective, hearing whatever it is from all sides.

Or do the bouncing waves interfere with whatever direct sound happens next, so the next direct sound is indistinct?

And yeah, I am working my way through the fabulous suggestions you all have posted, starting with the prosoundweb study hall page. Thanks a bunch!

#### gafftaper

##### Senior Team
Senior Team
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It all depends on the type of performance, the number of reflections, how and where they reflect... there is no simple answer. Some examples. My new theater is designed for acting and they have acoustically removed every reflection possible because you don't want to here a lot of resonance or echoes after a person speaks. In a classical or acoustical instrumental performance you want a lot of carefully designed reflections that will help the sound of the instrument expand, last a long time, and generally sound large and full. Rock concerts are somewhere in the middle with a lot of the sound being altered electronically you don't need a carefully designed space.

As for this community, while many theater technicians are helpful to new people just starting out, this group is an especially nice group. We are glad you are here.

#### museav

##### CBMod
CB Mods
Departed Member
This is starting to cover very large subject areas and could take pages and pages to even scratch the surface. Hopefully you will learn some ithings n school, including a lot of the theory and basics behind audio and acoustics, but much of itthe practical application may have to be learned through experience and other education.

For example, for reflections a simplified answer is that as gafftaper noted, it depends upon the application. Where you are relying heavily on the sound system for all audio, you typically want to eliminate reflections and reduce reverberation as much as possible, effectively removing the room and relying solely on teh sound system. For speech intelligibility the same may apply, however some natural reinforcement through specifc reflections and a slightly 'liver' space may be desired as well. For music performances, the environment becomes part of the performance and you start looking at aspects like Early Decay Times, Initial Time Delay Gap, Direct/Reflected energy ratios, Early/Late energy ratios, Clarity, Loudness, Spaciousness, Sound Strength and so on. What is really the issue is both the 'liveness' of the room in general and how a sound from the stage arrives at the listeners. In general, you do not want any very early arriving reflections and want a gap of maybe 10-20ms between the direct sound and the first reflected sound arrivals, this helps reinforce the direct sound and where it originated. For music you typically then want strong, diffuse and well distributed reflections, with a strong lateral component, for a certain time period with the levels of the reflections then decreasing over time. This gives the room warmth and spaciousness and is where the good halls really excel. The specific time periods may vary, but 50-80ms is typical. You almost always want to avoid and discrete, higher level late reflections as these are perceived as discrete echoes. Some of the same type of factors enter into churches and other spaces where audience interaction is desired, except in that case you are looking at reflections among the audience. And sometimes determining the goals for reflections is based simply perception, for example the lobby that people want to have perceived as being larger and grander than it really is may even want many late reflections and echoes.

Early reflections off surfaces can also affect the sound from the speakers. A speaker reproducing low frequency sounds located a few feet from a surface may result in reflections that cancel with the direct sound at some frequencies and sum at others.

Designing a sound system gets into first considering factors such as the intended use, the environment (the room), practical considerations such as where you can or cannot locate speakers and in the real world budget is almost always a factor. Only then can you start determining the appropriate performance requirements including frequency response, coverage, levels and so on. For spoken word you have to consider intelligibility. The requirements for a sound system to support rap or hip/hop may differ from those required for live acoustic performances even for the same room. A system that has to cover both as well as speech may need to have capabilities that exceed any single application. And this has just gotten you to where you are ready to start laying out the system and selecting devices.

Someone with experience may be able to look at a space and know what will or won't work, but it takes many good and bad experiences to get to that point. In fact, one of the biggest problems with all the acoustics and audio design tools out there is that while they are very powerful, many people using them have no idea what they really are doing and do not recognize when they get questionable results.

As long as this post is, it is just touching on a few of the basics. This is not in any way meant to scare anyone off, but simply to show just how complex it really can be.

#### icewolf08

##### CBMod
CB Mods
I think I have an issue with wanting to know everything, like yesterday. People here are so giving of themselves. Is that a trait specfic to technicians, do you think?
Why do things that absorb sound make the sound better? Is it because there are fewer waves bouncing back? There's a word for those waves, correct? The instructor calls them mukdamim.
I would have thought the bouncing waves after the initial sound would just make it that much more effective, hearing whatever it is from all sides.
Or do the bouncing waves interfere with whatever direct sound happens next, so the next direct sound is indistinct?
And yeah, I am working my way through the fabulous suggestions you all have posted, starting with the prosoundweb study hall page. Thanks a bunch!
I would venture to guess that mukdamim are either reflections or reverberations.

In addition to what gaff said, reflections can also cause distortion and make the sound muddy. Reflections can interfere with the original sound wave and make the sound unintelligible to the listener. Thus as gaff said, fewer reflections give a cleaner product.

There is nothing wrong with wanting to know everything. It is always good to know that there are people who really want to learn, and they usually make very good technicians. You will probably find that many technicians (not all) are willing to give as much as they can, especially here on CB. This is an ever evolving field, and we have to help eachother get a long.

#### miriam

##### Active Member
So lets see.

1 What type of performance, what are the sound needs
2 What is the space like, acoustics
3 What is the space like, dimensions (for placement)
4 How much am I willing to spend
5 Choose equipment
6 Set up
7 Make sure everything works
8 Make the kind of noise the show will have and play around with the reverberations

Or does #8 happen during the actual show? Is that what the mixing part is all about?

Should I start a new post now that we are so off topic?

#### mixmaster

##### Active Member
I have heard often that mixing a show is both an art and a science. The science is in designing a sound system (lots of math, algebra and geometry). If done correctly, this should give you a solid system that becomes the foundation of your mix. The art of mixing is bringing together all of the things that affect what people hear and making sense of it. You can use math to determine delay times, predict room reflections, set gain structures, and coordinate equipment. All the math in the world isn't going to help you know when something "seems too loud" or "doesn't sound right". At that point it's an art. It's all about your ears. People may tell you that a poorly designed system will never sound good but I have heard some real good engineers make bands sound good on "bad" systems. I have also heard terrible mixes on what should have been "good" rigs. The best I can say is that you need a good ear to be able mix and a good math background to be able to understand what is going on.

As to learning resources, In addition to PSW studyhall and Yamaha's books, I would recommend checking some manufacturer's websites. Often times they will have tech articles or "white papers" on subjects relevent to their products. I have found interesting articles about amps and speakers on the JBL website, and I think Soundcraft has some stuff on their webpages about mixing. The best education you will get is getting out and doing it. Find someone who you can hang out with and watch and ask questions. Most people are willing to share what they know. Read everything. Even if you don't understand what you read, you may hear that being discussed elsewhere and you can ask for clarification then.

Best of luck

#### museav

##### CBMod
CB Mods
Departed Member
I would say that the system design and mixing are both best approached as art and science. I have seen system designs and products that were technically correct and measured well, but simply did not sound good. I have to disagree a bit in that while knowing when something is too loud or doesn't sound good may not be perceived as math and physics, they do often help you understand why it is too loud, why it doesn't sound good and what you have to do to fix it. When you have two mics catching the same sound you may not actually think that to address the resulting summation you need to reduce each by 10log(2), but you may know that you should turn them down by around 3dB.

I do agree that it can be either the system or the use of it that are the limiting factor. You can't blame the equipment or the system for a poor mix and you can't blame the mixer for problems inherent in the system (or for the fact that guitarist turned up his stage amp to 11). In the end, the manufacturer and system designer have no control over the mix and all they can really do is provide a good foundation for the mixer to work from. The reality is also that many/most/all mixers have to work with less than ideal systems and environments. This is where a mixer having a solid understanding of acoustics and system design, and understanding how to work with the system's limitations rather than to fight them, can be a distinct benefit.