Friday, March 24, 2006

Flow with Me: The Basics of Sound and Sound Systems Part 1

Flow with Me: The Basics of Sound and Sound Systems

What is Sound??

Sound is acoustical energy that is created by vibrations in a medium (substance), and they travel in waves or rays. Without movement or vibrations, there is no sound! That’s why it is possible to hear underwater. In fact you can hear through cement if the vibrations are strong enough. We hear sound through the movement of the atmosphere or air. Sound moves at about 1,130 feet per second. Light moves at about 186,000 miles per second. That’s why you see lightning long before you hear it!

Here are a few things we need to know about sound so we can understand each other better.

Tech Terms

Sound waves have both frequency and amplitude that are measured in what we call Hertz.(or cycles per second)

Volume or Sound Pressure Levels or SPLs are measured in dB

We will talk more about sound waves later in the seminar. Right now we will talk about how sound systems work on an elementary level.

Simply, a sound system does 3 things:

1. It changes acoustic energy into electrical energy (microphones, DI boxes)
2. It manipulates the electrical energy (mixers, EQ, compressors, amplifiers).
3. It changes electrical energy back into acoustic energy (speakers, headphones etc.)

The different pieces of equipment that handle these tasks vary. Let’s talk about them.

Input Devices

Microphones convert acoustical energy into electrical energy.
All microphones do the same thing but in different ways.

1. Dynamic- converts to electrical energy by using magnets and a coil. (SM58)

2. Condenser- converts to electrical energy by using two externally charged plates. (C414, phantom power)

3. Electret- converts to electrical energy by using two permanently charged plates

4. Ribbon- converts to electrical energy by using magnets and a metal ribbon

5. Wireless- can be any of the above, but add a transmitter and receiver into the picture. We’ll talk about them in more detail later.

Electronic instruments (e.g. keyboards and electric guitars), CD and tape players, etc all generate electrical energy on their own. They output line level signals which are higher in signal strength than microphone level. In order to use them you may need a Direct Box which bumps the signal level down .

Signal Processors

There are many devices grouped into this category because they all have one thing in common. They all can alter the signals that go through them. Here are a few of the most common pieces of equipment:

1.Mixers- (from 4-8 channels up to 64-96 channels) ** I include mixers in
this category, most other people don’t. I will explain later**

2.Equalizers- (graphic and parametric)


4.Multi Effects like reverb, chorus etc...

5.Amplifiers( I include amps here because they in fact boost the signal level in oder to drive the speakers they are attached to. Many newer amps have digital processing built into them.)

All of these devices can be either analog or digital.

Output Devices

I can only think of one type of output device, but there are many different incarnations:

Speakers change electrical energy back into acoustical energy. Headphones, in ear monitors etc. are all forms of speakers. More on these in a second.

What is Signal Flow???

Signal flow is the way that the electrical signals move through your sound equipment.
I like to use water as a symbolism for sound. Imagine a system of water pipes. Our audio/electrical signal is the water flowing through them. The water can flow through small thin pipes, or big pipes. It can flow into tanks, ponds, etc. You can add colors to it to change the way it appears and then you can make it flow out into a glass. All these things can be though of as manipulating the water/signal.

Next post will get more detailed! Tell me if this info was helpful to you!!

Remember "Faith comes by hearing!"

Tuesday, March 21, 2006


Welcome to the Sound Doctrine Seminar blog!!

My name is Steve Croom. I am an audio engineer from Cleveland, Ohio. I have been in the business for over 15 years and have gotten a lot of experience in that time. I will post my resume for you to check out at a later time). The goal of this blog (and future podcasts) is for me to share my knowledge of audio with you. Although my target audience is the "church sound volunteer", I am sure that the information I will share will help just about anyone who is starting out in the field of live sound or studio recording.

I also offer training seminars periodically in the Cleveland area, and hopefully other cities soon. If you would like more information, please feel free to email me at or I would be glad to assist you if I can.

My next blog entry will be entitled "Flow with Me!". I will discuss some of the basics of sound and sound systems.

Stay "tuned" for more!!