Feel free to suggest additions to this page. I will add terms every now and then, but if there are specific terms you would like to see, I will make an effort to post those quickly.

Amplifier: A device that takes an audio signal and boosts it. These come in many forms, whether as “outboard” rack units that connect to speakers, preamplifiers within guitar amps, or one of many other articulations.

Attenuation: The act of reducing a signal level at a set amount rather than in a curve, as with a fader or a trim pot. This is often done in order to prevent “clipping,” which is a form of distortion caused by electronic overload of the circuits in audio equipment. Any sort of clipping and overload like this will damage equipment over time, though the severity and regularity may damage equipment very quickly rather than gradually.

Cable: A strand of metal fibers wound and bound in a non-conductive casing. This serve as the pathway for the voltage output of a source to reach the amplifier. Cables come in different types for different applications, with the most common being XLR cables (usually for microphones or speakers) and 1/4″ cables (usually for instruments or speakers). It is important to care for your cables properly, otherwise the metal fibers will degrade, causing many issues with the signal passing through, either introducing unwanted noise or stopping the signal altogether.

Equalizer: A device that can cut or boost specific frequency ranges so they are heard more prominently or less easily. Equalizers come in many forms, such as the parametric EQ (the Lo, Mid, and Hi knobs on a mixer are a type of parametric EQ) and the graphic EQ (seen as a series of faders each labeled with a different frequency. EQs are used to modify the timbre of a source, often with the goal of eliminating problem noises or carving out a personal niche in the overall mix. EQs often work better at cutting than boosting, and the less EQ used the more natural the sound will be to the human ear.

Frequency: The rate at which an object vibrates, measured in cycles per second, “hertz,” or “Hz.” The human ear is generally considered to be able to pick up vibrations from 20Hz to 20MHz (20,000HZ).

Fundamental Frequency: The loudest frequency of a sound. This is the pitch discerned by the ear as opposed to the overtones ringing simultaneously with the fundamental frequency. The fundamental frequency is the measured Hz, not the overtones.

Gate: Also known as an “Expander,” a gate is designed to eliminate excess noise and bleed from secondary sources, such as cymbals on a snare mic. The way it works is that it “closes” (lowers the volume) and “opens” (returns volume to normal) as the signal strength decreases and increases. For example, if the gate is set to close when the level drops below -10dB, the signal will be cut on a curve much as a signal is cut on a curve when a compressor reins in an especially loud passage in a song. In the case of a drum set, the snare mic may be picking up the hi-hat while it is being played, since the two kit pieces are so close together. If someone turned down the snare channel fader whenever it is not being played, there would be that much less noise in the system. A gate does this automatically, just as a compressor automatically lowers the level on a transgressing signal peak.

Ground Loop: A ground loop is manifested in an audio system as a hum, and it is caused by grounding issues in the electrical system in a facility. The grounding of a given piece of equipment in an audio system should each have only one, single pathway to the earth. If a piece of equipment has multiple paths, the different paths cause a loop of sorts (imagine four points: audio device, ground path, earth, and ground path, all linked in an electrical circle) and cause hum in a system, traceable to particular “offending” equipment. There are different methods of fixing a ground loop, probably the most common of which is a “ground lift” switch. A simpler method is by using a three-to two-prong adapter, but this is considered extremely dangerous since it eliminates the safety granted by grounding in the first place. Ground paths can be found not only through a power outlet but through the chassis of a rack unit (from one unit to the next), through the shielding of an audio cable, and other places. Eliminate all but one ground path per device and it will be gone. Ideally, your entire audio system will have a dedicated AC circuit and thus a single path to ground, but that is rarely the case in real life situations.

Mic/Microphone: A device that transforms physical vibrations into an electrical current and sends it out to be mixed and amplified. They come in different styles, such as dynamic, condenser, and ribbon microphones. Each has its own pros and cons, whether in price, function, or durability. Mics can be handheld or clip onto the source, such as a lapel mic or the mic on a trumpet bell. They are used for capturing sounds from the human voice, guitars, percussion instruments, nature, and many other places. They are as specialized as a driver’s license stamp and can cost anywhere from $50 to $5,000. The style and type of microphone varies greatly from one application to the next, and there are plenty of guides on selecting the correct mic for the job.

Mixer: Also known as a Sound Board, this is a device that adjusts the levels and otherwise tweaks various signals before sending them on to amplifiers in order to be heard by the intended audience. They come in many forms, including digital vs. analog, pots (knobs) and/or faders (aka “sliders”), small (2 channels) or large (96 channels), etc.

Overtone: A frequency that vibrates alongside the “fundamental frequency” of a sound. Overtones are virtually indiscernible in most cases, leaving the fundamental frequency that which is recognized by the ear. Overtones come in a series above the fundamental frequency in a set pattern, depending on what type the source is. Overtones are what give a sound its unique timbre, what makes it sound different than everything else — trumpets sound different than dog barks, etc. Overtones may be boosted or hindered by any number of things, such as the type of materials used in the construction of an instrument, the nasal passageways in the head, the room in which the source is located, or an equalizer.

PA System: “Public Address System,” also known as a “Sound System.” A collection of devices that, working together, provide a means for an individual or group to communicate with a large group of people. Music, sermons, and speeches are a few uses of a PA System.

Pad: An internal component in many audio devices such as DIs and mixers that attenuates the signal to a preset degree, often initiated by a button or switch and with varying standard dB attenuation based on the unit in question (e.g. -4 or -10 dB).

Phantom Power: Phantom power is a simple yet ingenious system of delivering power to items on stage without the need to run power cables or use batteries. Certain microphones, DIs, etc. require a certain amount of electricity in order to operate, unlike the typical dynamic microphone. Some mixers have a single button, but many have individual buttons per channel. What happens is the mixer sends a low voltage (48v, to be exact) out through the audio line to power the equipment on stage, which are then able to send the signal back through those same cables. No extra wiring, no extra batteries to change.

 Phase: The position in a recurring cycle in the sine wave of an audio signal. When phase cancellation occurs, two copies of the same signal are “out of phase” with one another — that is, when one copy is at the peak of the sine wave, the other copy is in the valley. The result is in opposite sine waves cancelling each other out, with the brain interpreting silence instead of noise.

Signal: The voltage coming from a source that is then manipulated and amplified. If it is loud, it is sometimes called “high” or “hot,” while quiet signals are often called “low.”

Sound Board: See Mixer.

Sound System: See PA System.

Speaker: Usually a cone made of paper, plastic, or other stiff materials, this is the device that takes the signal from an amplifier and transforms it into physical vibrations. In general, a magnet moves forward and backward in the rear, causing the cone to move in and out. This creates vibrations in the air according to the speed and intensity of the magnet’s movement, thus creating a broad range of frequencies that, when heard together, ideally make a sound recognizable as a guitar, a voice, or whatever the source is sending as a signal to the system.