You wonder why the band is bringing in speakers and amps, after all the club has its own sound system evidenced by a couple of big rectangular speakers on either side of the stage each atop other really big square speakers. Also there are what look like four smaller speakers facing backward on stage. A skinny guy, looking too old for the club but staying cool by sporting a ponytail and tattoos, is running around plugging things in and setting up mics. He puts about five mics around the drum kit, hangs one in front of a guitar amp, he sets up a couple of mics on stands toward the front of the stage and then plugs the keyboards and bass amp into the club’s system. This guy is the club’s “sound god”. If he’s good, he can make a really lousy band sound OK and an OK band sound great. If he’s not so good, he can make a great band sound really bad.

After the sound guy checks all the mics and lines he heads over to a rack of electronics off to the side of the stage and starts turning things on. Now he moves to the back of the room and takes up station behind the soundboard—this thing looks like the console on the Star Ship Enterprise, only with more knobs. Next, he puts on a set of earmuff type headphones, lights a cigarette and sits down. His show is about to begin.

He doesn’t wear the headphones over both ears. One pad covers his right ear, the other is pressing against his temple—this way he can simultaneously sample the sound directly from the board’s input lines and from the main speakers. He picks up a microphone and speaks, “OK, guys let’s start with the drums.” As he moves from drums to the other instruments and vocals, his goal is to use the tools offered by the sound board to accentuate each output’s timbre while eliminating any annoying sounds. Once he’s happy with what’s coming out of the main speakers he turns his attention to the backward facing speakers—the monitors.

The band has to hear itself and that’s what the monitors are for. This part can get tricky. It’s where feedback most often happens. Too much of the wrong pitch coming from a monitor and hitting one of the mics or causing guitar strings to vibrate can set up a vicious circle of sound; the quickly increasing high pitched screech of feedback.

In the next few articles I’m going to impart the knowledge necessary for anyone to become a skinny, slightly over-the-hill dude with a ponytail and tattoos. I’ll begin below covering the basics of “sound”; what it is, what we hear and why, and what makes a good sounding room. The next article will cover sound system equipment. In the final article we’ll put it all together; talking about the magic of EQ’ing, proper volume mixing and the pros and cons of running sound in an alcohol-serving environment.

Basic Sound

Sound is just a series of pressure changes, fluctuations or waves, traveling through the air. At room temperature (72 o Fahrenheit) “sound waves” travel at about 773 miles per hour which is 1132 feet per second. Being pretty close to 1,000 feet per second, it makes for an easy way to estimate how far away things like lightening strikes are—you see the flash, count the number of seconds until you hear the thunder and multiply by 1,000. The speed at which sound travels drops as the air temperature drops and speeds up as the temperature goes up.

There are two basic types of waves that we’re familiar with-- lateral waves and compression waves. In lateral waves “stuff” is displaced up and down as the wave moves along. Imagine one end of a rope affixed to a wall and then the rope pulled taught. If you give the loose end a flick a small section of the rope displaces up and another section displaces down, and these sections follow each other along the length of the rope. A compression wave is a bit different—the “stuff” bunches-up and spreads-out. Think of a slinky attached to the wall and pulled taught. If you give the free end a quick push-then-pull, a bunched-up followed by a spread-out section will move down the slinky. Sound is a type of compression wave where the “stuff” being bunched-up and spread-out are air molecules—pressure fluctuations.

Picturing Sound

You can get a good visual representation of sound by plotting the pressure fluctuations as either a function of time or distance; the speed of sound easily relates the two. We interpret the magnitude of the pressure fluctuations as loudness and their rapidity as tone. Loudness is usually measured in units of decibels (dB). For a pure tone, either plot will look like your High School Trigonometry Class' sine wave plot. On the time plot, the measure from one peak to the next is the wave’s period—the inverse of that is its frequency. The unit of frequency is the Hertz (Hz); 10 fluctuations are 10 Hz, 100 fluctuations are 100 Hz and so on. On the distance plot, the measure from one peak to the next is the wavelength.

Instruments don’t produce pure tones. Each produces a unique timbre that is the result of a combination of sound waves adding together. The major repeating peak in the instrument's sound plot identifies a particular note.

Two Sine Waves Adding Together
To Form A Complex Wave

What We Hear

Our anatomy and physiology determine what we hear. If the sound is too soft or too loud, we won’t hear it. In fact if it’s too loud it can damage our ears. Also, we can only hear a certain range of frequencies. An interesting phenomenon is that we can hear some frequencies within that range better than others. Most people are very sensitive to frequencies around 4,000 Hz with sensitivity dropping off more rappidly at higher frequencies than at lower ones. This is due to the shape of our heads and the placement of our ears.

Here are some "loudness" examples:

Below I list some common noise sorces, their sound wave frequencies and sound wavelengths:

A Good Sounding Room

We saw above that sound waves can add together to produce the unique timbre of an instrument. We also know that sound bounces off hard surfaces—who hasn’t heard an echo after yelling in a cave or tunnel? This is all good for instruments and for caves, but it’s not good for live music venues. A good music room or venue should be as acoustically neutral as possible. There shouldn’t be echoes or dead spots (caused by the combining of reflected and oncoming sound waves).

Making a room acoustically neutral isn’t too hard if the room has only one purpose like a recording studio. But live music venues are often multipurposed. Hard floors and brick walls work for a bar or restaurant because they’re easy to clean and low maintenance, but they’re a killer if you want good sound. The idea is to have floors, walls and ceiling in soft materials; carpet, fabrics--the types of materials that absorb rather than reflect sound.

Another consideration is the size and shape of the room. You can minimize dead spots by not facing speakers directly at walls and not placing them within whole multiples of your instrumnets' lowest note wavelengths. As an example, if you face a speakers at a wall 72ft away you'll create dead spots for your kick drum.

If a club isn’t sound friendly, there is one other thing that can be done. Only book bands that draw large crowds—bodies absorb sound real well.