If you pay attention to sound at all, you love to hear a great echo. Think about standing next to someone at the edge of a large canyon, listening to them shout and waiting to hear the reflection off the other side of the canyon. As we stand beside him, we will first hear the sound of his voice on a path directly to our ears.

Moments later, we will hear his voice repeated after the sound wave has traveled across the canyon and back to our ears.

There is a delay to the arrival of that reflected sound caused by the time it takes for the sound to travel (at roughly 1,130 ft/sec) out to the canyon wall and back to our ears. It's fun listening to a train come through my home town.

On a quiet night you can hear the train horn off in the distance, followed by multiple reflections of the sound spread way out in time. As the sound bounces off large buildings, the echo can trail on literally for a couple of seconds. Way cool! This same type of delayed echo of a sound occurs in a room as well, and is caused by the sound reflecting off of surfaces in the room and finding its way back to our ears.

We will hear the original sound as a reference, and that is followed quickly by the early reflections or echoes. How apparent those echoes sound is relative to how loud they are and their arrival time.

The loudness is a function of the material it happens to reflect off of. This can also alter the frequency content of the sound, since that material may reflect certain frequencies quite well and yet absorb others. The arrival time back at the listener's ears is a function of how far the sound had to travel through its reflected path to arrive at our ears, and is of course, relative to the arrival of the direct sound.

Some reflections may not even be able to be heard, even though they can be measured and proven to be quite loud by comparison. If the sound is delayed in time by less than about thirty milliseconds, our brain will not perceive it as a discrete echo.

So, reflections arriving less than thirty milliseconds after the direct sound arrives might be considered early reflections. Reflections that arrive thirty milliseconds or so after the direct sound arrival will generally be heard as discrete echoes. This effect is typically more noticeable with sounds that have a percussive attack, and this is why clapping your hands is an acceptable method of examining your situation.

When you clap your hands in a large enough auditorium, you may notice a smoothly decaying sound that lingers for a moment. This is know as reverberation, and is made up of many hundreds of reflections arriving at the listener's ears, so closely spaced in time that he cannot perceive them as separate echoes, but rather as a homogeneous mixture of all of them.

Each room has its own reverberation sound character, determined by the acoustics of the room. That is to say, the manner in which the room is constructed - how large it is, if the surfaces are hard or soft, reflective or absorbent, even whether they are painted or not, and so forth - gives the room its acoustic signature.

Part of that character is the sound of the reverb. For example, a large room with a great deal of thin, soft absorbent material may attenuate the lingering high frequencies of the reverberant field rather quickly while the lower frequencies of that reverberant field carry on longer.

Proper design would present a reverberant field that is quite diffuse, with all frequencies decaying smoothly together, and no one frequency louder than another. Today, any of these acoustic properties of rooms, big or small, reverberant or not, and even those of the canyon wall, can jump into the sanctuary at the touch of a button.

The ever-diminishing price of digital technology has brought forth a plethora of affordable digital effects processors. Offered by a host of different manufacturers, digital effects processors are typically multi-talented, in that they may be capable of simulating literally any of the effects described above along with a long list of other, more imaginative or not-exactly-natural-on-the-planet-I-know-and-love effects.

Quite literally, whenever I'm mixing an album I imagine a place where this performance is taking place, and then use the effects processors to help shape or define that place.

Similarly, doing a sound reinforcement mix to me is really just mixing the album in front of an audience instead of in a small control room. As long as the room is large enough and relatively well behaved acoustically, I approach the use of digital effects processors in exactly the same way as during a mixdown session.

Remember, a little bit goes a long way. Don't overdo it! One secret to learning how to use effects tastefully is to listen very closely to your favorite albums and model how they are used. What effects are used, on what sound sources, and how loud are the effects in the mix?

A good model for your live worship music mix can be found in your favorite contemporary Christian music and live worship recordings. You'll hear very tasteful use of effects. Carefully analyze how the engineer achieved that sound, and then simply emulate and incorporate those ideas into your own services. It's helpful to set up your reverb device so that you can easily adjust the reverb time for each song.

Who says your effects settings need to stay the same throughout the service? I'm a strong believer in manipulating the effects to suit the song, even if that means making changes between every song. Let's say that you've set the reverb time for a long decay that sounds great for a slow, worshipful song. But if the next song happens to be an up-tempo praise song, that long decay is going to make your mix sound muddy.

By comparison, if you have the decay set fairly short so it works great for a fast moving song, that reverb sound will seem unnatural and out of place during a slow moving song. The idea is to let the reverb decay get out of the way before the next beat. In other words, count along or pat your leg with the tempo of the song, and find a reverb time setting that will decay in one beat.

Or grab a mic and click your tongue in tempo with the song to excite the reverb, and make sure that the decay isn't spilling too far into the next beat. This process is clearly entertaining for your friends and relatives. Do this during rehearsal for each song, and mark the reverb time settings on your song set list. Then you'll easily be able to make the appropriate adjustments throughout the worship set.

It's not worth getting too detailed about this. If two or three songs have roughly the same tempo, I'll leave the reverb time setting alone. But I will change it if the tempo changes substantially. If the song has already started and you didn't get to do this during rehearsal, use the beat of the snare drum or even the worship leader's vocal to help you set the reverb time.

I love to add a delay on occasion to individual elements like the lead vocal, a saxophone or guitar solo, or sometimes to the backing vocals. Carefully used, it can add tremendous depth to the mix. Here again, pay attention to the tempo of the song, and set the repeat time of the delay to match the tempo of the song.

The delay effect can be a powerful enhancement to the song, or a chaotic distraction. A seasoned mixer will set the timing of the repeat to the tempo of the song, and adjust the number of repeats to the level of the effect to blend with the song. Too loud and/or too many repeats and it's in the way, too soft and it won't be appreciated. Your mix will be cleaner if you keep the repeats back to one or two.

Look for a delay device that has a tap feature, preferably a unit that allows you to set the tap using a footswitch. Tapping the switch once sets the counter to zero, tapping it a second time starts a clock counting in milliseconds, and tapping it a third time stops the clock and sets the delay time between repeats to the value on the clock.

If I can tap my foot three times to the beat of a song - something my degree in music and eighteen years of playing in bands has allowed me to master - then I can quickly and accurately set the delay time for the song. Phasing, flanging, and chorusing are various examples of time modulation.

The signal is messed with in the time domain, and then mixed with the original to produce the result. The most powerful effect of the three is flanging. The term came from how the effect was originally created. As the story goes, on a Jimi Hendrix recording project, it was discovered that a powerful phase shifting effect could be created by listening to the output of two tape decks simultaneously.

You start by recording the output of the multi-track mix simultaneously onto two reel-to-reel stereo recording decks, known as 2-tracks. Then set the monitoring switches so you listen to both of those 2-tracks together - something that wouldn't ordinarily make sense to do. They discovered that by having someone rest their thumb on the flange of the supply reel on one of the two decks, it would delay the playback signal of that source.

With the delayed signal arriving slightly out of phase with the other, God's laws of physics says that phase cancellations will occur. That is, some frequencies will cancel, while others will be increased. If you were only listening to the deck that you were messing with in time, you wouldn't notice much of a change.

The impact comes when you hear both of them together. Phasing is similar in nature to flanging, but not as strong of an effect. If you think about it, both are created by varying the delayed side of the signal with a very low frequency oscillator, cyclically slowing down the signal and then bringing it back to normal speed.

Chorusing is basically the same circuit, but instead of modulating the time domain of the signal with a low frequency oscillator, it's modulated with pink noise.

Something I haven't mentioned up to now is the dry-to-wet ratio, sometimes labeled mix on the front panel of an effects device. A totally reverberant sound might be cool for a special effect, but not for your general reverb use. And the output of a digital delay unit wouldn't make much sense without the listener hearing the original sound source.

The power of these effects is in how they are mixed with the original sound. So we need some way to control that blend. In most cases, you'll connect the effects device so that it is fed from a postfade auxiliary send on your console. The output of the effects device comes back into the console at the auxiliary return input, or on a spare channel. In this application, you want to set the mix knob on the unit all the way to the wet position.

That ensures that only the effect is being heard at the aux return. You'll establish your dry-to-wet ratio by adjusting the aux send knob on each channel. If these effects devices were only being used with consoles in the manner I've just described, there would be no need for the mix knob.

But a guitar player, for example, might want to use it just with his rig. With the mix knob in the dry position, he'll hear only the direct sound from his guitar. With the knob in the wet position, he'll hear only the effect. The mix knob allows him to control the balance between those two sounds to achieve the blend he's looking for.
When All Else Fails

The only way you will ever become adept at using these devices is to read the operator's manual - y'know, that book that's still in the box somewhere - and then experiment. Now, I'm guilty too. I often operate by the motto - when all else fails, read the directions. So learn from my shortcomings and do what I teach. The time to experiment is first on your own, then during rehearsals. Then apply what you've learned in a deliberate, creative effort during a service, maybe during the midweek service first, to get used to it. The unspoken caution here is, don't experiment with the effects during a service, at least not until you are very comfortable with the device and know what you are doing with it.

Even then, approach its use with care. One good way to force yourself to learn the unit is working with a singer and accompaniment tapes. Whenever I'm in this situation, I listen to what the original track is doing with regard to the lead vocalist's effects. Then I listen to the accompaniment track by itself to see what delays and reverb sounds are still there.

And finally, during rehearsal I'll try to enhance the singer's voice very much like the original recording did. With those effects happening, and with the track loud enough over the system to be realistic, the end result is quite believable. One more comment regarding the use of these effects.

When the song is over, be certain that the aux returns receiving the signal from the delays and reverb are off before the pastor or anyone, including the vocalists, begins to speak. It's terribly embarrassing to hear a long, repeating delay of the pastor's voice thanking the vocalists for their musical offering.

Of course, that's never happened to meS¹. Well, hopefully this has helped. Don't be afraid to use effects in your service. Tastefully applied, they can bring new depth and dimension to the sound of your music. And most importantly, have fun!
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Summary of Acoustic Effects

* Reverberation - many repetitions, becoming more densely spaced with time.
* Echo - one or a few discrete repetitions of an audio signal.
* Delay - the time interval between a direct signal and its echo.
* Decay - the time it takes for echoes or reverberation to fade away. And we can summarize the different techniques available for simulating these techniques this way:
* Echo Chamber - In effect an acoustic means of creating an artificial reverb by setting speakers in a large room and picking up the resulting sound with microphones.
* Plate Reverb - constructed of a large sheet of metal or foil which is suspended from its corners. It has a small speaker mounted on the sheet, which makes it vibrate, after which two widely spaced contact microphones pickup the resulting vibrations. In its day, this was the brightest-sounding and most popular type.
* Spring Reverb - A cost-effective unit. Less expensive types are often characterized by a twangy sound when driven too hard. Analog Effects Devices - Electronic devices which use an analog bucket-brigade circuitry to provide signal delays and reverb sounds.
* Digital Effects Processors - Because of their flexibility, variety of sounds, and control over individual parameters, digital effects processors have replaced the majority of other reverb types. Kudos to the engineers and DSP software engineers who have developed and written the algorithms that make these units so spectacular.