David's Blog is a space where I hope to share some of the things I have learned over my 30 plus years in and around the audio business and my time training as an Audio Engineer and as a performing Musician and Composer. I will be including hints, tips and some tried and true methods that will help audio enthusiusts of all levels to get the most out of their investment. I am starting with a glossary of terms and jargon used in our industry. Check back for my first article entitled "What is good sound and how do I get it?".

David Jensen

Click Here to listen to my cover version of Pink Floyd's "Mother" taken from ny forth coming album entitled "The Dark Mirror"


Glossary Of Audio Terms


 A


AC Short for Alternating Current - Electrical current that alternates it's polarity or direction.


Absorption The tendency of sound waves to be soaked up by soft surfaces. Opposite: reflection.


Acoustic Feedback Feedback is the result of sound leaving a speaker and entering back into a microphone. Sounds like a sustained shriek - is a self-perpetuating cycle which can be stopped by decreasing the volume


Acoustics The properties of a room or environment that affect the qualities of sound.


Acoustic Suspension A type of speaker cabinet which is sealed to control the action of its woofer and prevent the leakage of air.


Ambient Noise Level "Background" noise - from any source - that affects the listener's ability to hear what is produced by a sound system. Machinery, hum from florescent lights, traffic, etc.


Amperes, Amperage (Amps) Units of electrical current.


Amplifier (Amp) An electronic device that increases the strength of a signal. also See preamp, power amplifier, Phono Preamp


Amplitude The strength of sound waves or an electrical signal.


Anechoic 1. The complete absence of reflected sound (echo). 2. An environment that prevents (through dissipation and absorption of sound waves) all reflected sound, as in an anechoic chamber.


Attenuate To make weaker.


B


Balanced Line A type of cable used when long lengths are needed. Balanced signals utilize a natural occuring cancelation effect that reduces the noise picked up by longer lengths of cables.


Basket The frame to which a driver's cone is mounted.


Bass The lower end of the frequency range, from about 20 Hz to about 300 Hz.


Bass Reflex A speaker that, as a means of enhancing the efficiency of the reproduction of bass frequencies, channels some of the sound pressure generated by its woofer(s) through an opening (port) in its cabinet.


Biamplification The use of separate amplifiers to power woofers and tweeters.


Board Control board or mixing console


C


CPS (Cycles Per Second) The number of plus/minus voltage swings or compressions/rarefactions of air molecules occurring each second in an electrical or audio signal; usually expressed as hertz (Hz).


Cardioid Heart shaped pattern exhibited by some microphones which reduces pick-up from the sides and back.


Clipping Audible distortion that occurs when an amplifier is pushed beyond it's limit. Clipping refers to the wave form of the sound having their tops and bottoms cut off. Clipping is one of the biggest causes of speaker damage.


Compression Driver A transducer, designed for use with a horn, which utilizes a diaphragm (rather than a cone) to reproduce mid and high frequencies. Laso see Horn


Compressor A device that squeezes the sound into a narrow band and reduces dynamic range. Most pop/rock recordings suffer from over use of compression making them sound lean and aggressive.


Condenser Microphone A mic that depends on an external power supply or battery to function.


Conductor A substance, usually a metal - that allows the free flow of electrons. ie copper, silver, gold.


Cone The vibrating diaphragm, employed in some speakers designs, that generates sound waves.


Console A large or elaborate mixer required to massage the ego of the band's sound man.


Critical Distance The distance from a sound source at which sound pressure levels emitted by the source equal those being reflected off of other surfaces.


Crossover A circuit that splits up an audio signal into sections suitable for woofers and tweeters etc. crossovers can be either passive (as found in most speakers) or active (as found in multi amplifier configurations).


Current The movement or flow of electrons. Also refered to as amperage.


D


dB (Decibel) 1. A relative unit of measure between two sound or audio signal levels. A difference 1 dB is considered to be the smallest that can be detected by the human ear. An increase of 6 dB equals twice the sound pressure. 2. As a measure of sound pressure levels, used to indicate loudness.


DC Short for Direct Current. Electrical current that flows in only one direction.


Delay 1. The postponement of an audio signal for a specific amount of time, usually measured in milliseconds. 2. A device designed to delay an audio signal.


Diaphragm 1. The radiating surface of a compression driver; its vibrations emit sound waves. 2. The moving element of a microphone.


Directivity The ability of a speaker or horn to direct sound to a given area which can be described by its directivity factor (Q).


Dispersion The area throughout which the sound produced by a speaker is distributed.


Distortion Any discrepancy between the source material and the output of a sound system.


Ducking The use of an electronic device to automatically reduce the volume of music or other background fill when an announcer begins speaking.


Dynamic Microphone A microphone that converts sound into electrical pulses by means of a moving electromagnetic coil.


Dynamic Range The difference between the softest and loudest extremes within an audio signal.


Dynamics Processing The use of electronic devices to control the levels of audio signals and compress or expand their dynamic range.


E


Effects Loop inputs and outputs that allow the sending of an audio signal to and from a signal processor such as a reverb unit, delay, gate or limiter.


Efficiency The ratio of a device's energy output to its energy intake.


Electret Microphone A condenser microphone which, instead of employing an external high voltage power source, relies on permanently polarized plates, a low voltage power supply, and internal preamp.


Equalization (EQ) The electronic manipulation of specific frequencies.


Equalizer (EQ) A device that permits the precise control of specific frequency ranges. Examples are: Graphic, Parametric, Notch Filter, Cut only.


Expander an electronic device that increases dynamic range by reducing a signal's level any time it falls below a specific threshold.


F


Fader another way of saying level control. Typically refers to level controls on a mixer.


Feedback See Acoustic Feedback


FerroFluid An emulsion containing metal particles, used to conduct heat away from a speaker's voice coil.


Filter A device that removes unwanted frequencies or noise from a signal.


Flat The state of an audio signal or tone whose frequency is unaltered by equalization. On most mixers and equalizers flat is indicated by the tone controls being at dead center.


Fletcher Munson Curve A graphic representation of average hearing responses of carbon based units at particular sound pressure levels.


Foldback an output, that by splitting an input signal (independently of the mixer controls), allows that signal to be sent a separate device. Foldback makes it possible for a performer to create his/her own monitor mix without affecting the front of house mix.


Frequency 1. The number of sound waves that pass a given point in one second. 2. The determiner of pitch.


Frequency Response The range of frequencies that are reproducible by a speaker or electronic component.


Front of House (FOH) the components of a PA that are directed toward the audience, as opposed to the back of the house or monitor system.


G


Gain Refers to the amount an amplifier increases the strength of the signal


Gate An electronic device that increases dynamic range by cutting off a signal when its level falls below a specific threshold. Used to control leakage of sound source into adjacent mics (ie drums).


H


Hz (Hertz) A unit of measure that equals one cycle per second.


High Pass Filter A circuit that allows only the high frequencies to pass.


Horn An acoustical transformer which, when coupled to a driver, provides directivity and increases the driver's loudness.


Hpercardioid A narrower heart-shaped pick-up pattern than that of cardioid microphones.


I


Impedance The measure of total resistance to the current flow in an alternating current circuit; expressed in ohms, as a characteristic of electrical devices (particularly speakers and microphones). Most speakers are rated at 8 ohms. Microphones are usually classified as being either high impedance (10,000 ohms or greater) or low impedance (50 to 250 ohms).


Inductance A circuit's opposition to a change in current flow.


Input Overload Distortion Distortion caused by too great an input signal being directed to an amplifier or preamplifier. Input overload distortion is not affected by volume control settings and most frequently occurs when mics are positioned too close to the sound source. Input overload distortion is controllable through the use of an attenuator.


Inverse Square Law The law that states that in the absence of reflective surfaces, sound pressure falls off at a rate inverse to the square of the distance from its source. In other words, every time you double your distance from the sound source, the sound pressure level is reduced by 6 dB.


J


Jack A female input or output connector


K


L


Limiter A device that electronically controls or "limits" the peak levels of program material.


Line Level A signal whose voltage is between approximately 0.310 volts and 10 volts across a load of 600 ohms or greater.


Load Any device to which power is delivered ie a speaker


Low Pass Filter A circuit that allows only the low frequencies to pass.


M


Microphone Processor A device that, when installed between a mic and an amp or preamp, allows the manipulation of the signal originating at the mic.


Mixer An electronic device that permits the combining of a number of inputs into one or more outputs.


Monitor A speaker or earphone dedicated to making it possible for a performer to hear - or monitor - his/her own performance. Examples are: floor wedges, sidefills, or mini-monitor.


Motor The magnet structure of a speaker


N


Noise Gate A device that shuts off a signal when the level falls below a preset threshold.


O


Ohm The basic unit of measurement of resistance.


OHM'S Law The law that states the relationship between current, resistance and voltage in an electrical circuit: Amperage times resistance equals applied voltage.


Omnidirectional Capable of picking-up sound or radiating sound equally from all directions; as with an unidirectional microphone or subwoofer.


Oscilloscope An electronic device that displays, on a video screen, a representation of an electrical signal.


P


PA Abbreviation of public address system: one or more speakers connected to an amplifier; may include a mixer and any combination of sound reinforcement devices.


Pad An attenuator


Patch Cord A short electrical cable used to connect individual components of a sound system


Piezo Tweeter A driver which is dedicated to the reproduction of very high frequencies and operated by means of a crystal rather than an electromagnet.


Phantom Power Operating voltage supplied to a condenser mic by a mixer or external power source.


Phase The relationship of an audio signal or sound wave to a specific time reference.


Phase shift The phase relationship of two signals at a given time, or the phase change of a signal over an interval of time.


Pitch Tone: A function of frequency.


Polarity A condition which has two states (in or out) and is usually described in one of three ways: 1. Acoustical to electrical (microphone): Positive pressure at diaphragm produces positive voltage at pin 2 of XLR or at the tip of a 1/4-inch phone plug. 2. Electrical to acoustic: Positive voltage into the "plus" terminal of a speaker causes the speaker's diaphragm to move forward (produces positive pressure). 3. Electrical to electrical: Positive voltage into pin 2 of an XLR plug or at the tip of a 1/4-inch phone plug produces positive voltage at the output (pin 2 of XLR jack, the tip of a 1/4-inch phone plug, or the red (plus) connector of a binding post (banana terminal)).


Potentiometer (Pot) A variable resistor (rotary or linear) used to control volume, tone, or other functions of an electronic device.


Power AmplifierAn electronic device that increases the volume of a signal. A basic unit of all sound systems. Power amps are typically connected to a preamp which provides controls for individual functions: level, tone, etc.


Preamplifier Also refered to as control amplifier. Adjusts volume, switches inputs etc.


Phono Preamplifier Does two jobs. 1. Increases the signal level of a phono cartridge so that it is strong enough to drive a standard preamp or integrated amp. 2. Re-equalizes the bass and treble levels back to original as per RIAA specs.


Proximity Effect An increase in the bass response of some mics as the distance between the mic and its sound source is decreased


Q


Q A ratio obtained by complex mathematical calculations involving the relationship of a speaker's direct radiated energy to its total radiated energy (directivity index). When measured on-axis, Q (which is dependent on frequency) is used to determine a speaker's suitability for a particular application.


R


Radio Frequency Interference (RFI) Radio signals from external sources that invade and can be heard through, sound systems.


Reflection A term that describes the amount of sound "bouncing" off of hard surfaces.


Rejection A microphone's ability to selectively exclude sounds coming from outside it's pickup pattern.


Resistance Opposition measured in ohms to the flow of electrical current.


Reverberation sound waves that continue to bounce around a space after the sound source has ended.


RIAA RIAA equalization is a form of pre-emphasis on recording and de-emphasis on playback. A vinyl LP is made with the low frequencies reduced and the high frequencies boosted, and on playback the phono preamp reverses the process. The net result is a flat frequency response, but with a reduction in noise such as hiss and clicks that arise from the recording medium.


S


SPL (Sound Pressure Level) A measurement of the volume of sound, expressed in decibels (dB): a function of amplitude.


Sensitivity The amount a volume a speaker can produce with 1 watt at a distance of 1 meter.


Shield A metal enclosure that prevents electronic components from being affected by unwanted interference. Shielded speakers may be placed near a TV, for instance, because their magnets cannot affect the picture tube.

Shelving The setting of the on-axis output of complementary drivers (woofers, mid-range, tweeters) to provide the desired frequency response.

Sibilance A hissing sound produced when pronouncing S and Z. Sibilance is undesirable and is often caused by poor setup of a turntable's tone arm or a stereo component with phase problems.


Signal An electrical wave.


Signal-To-Noise-Ratio The ratio the reproduced sound and background noise.


Sound Level Meter A device that measures, in dB, the volume level of sound.


Sound Pressure Level (SPL) The measurement of loudness, or amplitude, of sound, expressed in dB.


Spider An internal speaker component whose function is to precisely position the voice coil in relation to the magnet.


T


Toe-in Refers to the angle which speakers are angled toward each other.


Transducer A device which converts sound into electrical energy (a phono cartridge, microphone), or electrical energy into sound (a speaker).


Transformer A device that either reduces or increase voltage or impedance.


Tweeter A speaker (driver) that reproduces only frequencies above a certain range, usually about 2 kHz.


U


Unbalanced Cable that consists of one conductor and a shield. Also refered toas an RCA cable


Unidirectional A mic that picks up sound primarily from one direction.


V


Voice Coil Wire, usually copper, wrapped around a former (tubular core). When attached to a cone or diaphragm, surrounded by a magnetic field, and set into vibration by an alternating current, a voice coil causes a speaker to emit sound waves.


Voltag The electrical pressure (electromotive force) of a current within a circuit.


W


Watt 1. A unit of measurement that represents the amount of power an amplifier can produce. Watts are derived by the following equation Volts x Current / Impedance.


Woofer A speaker (driver) that reproduces only frequencies below a certain range, usually about 2500 Hz.


X


XLR Connector A three pin connector widely used in the audio industry.


Y


Z