A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

AMBIENCE Room acoustics or natural reverberation.

AMPLIFIER A device which enables an input signal to control power from a source independent of the signal and thus be capable of delivering an output which bears some relationship to, and is generally greater then, the input signal.

AMPLIFIER, POWER An amplifier which drives a utilisation device such as a loudspeaker.

AMPLIFY To strengthen a given electrical signal by increasing its amplitude, or raising its level - a sound term. The opposite of attenuate.

ATTENUATE To weaken a given electrical signal by reducing its level (usually by means of a volume or loudness control).

ATTENUATION A decrease in signal magnitude from one point to another, or the process causing this decrease.

ATTENUATOR An adjustable passive network which reduces the power level of a signal without introducing appreciable distortion.

AUDIBLE TONES, also AUDIBLE FREQUENCIES Sounds with wave frequencies which the average human can hear and which range from 15 to 15,000 Hertz.

AUDIO FREQUENCY Any frequency corresponding to a normally audible sound wave, usually 20 to 20,000 cycles per second.

AUDIO FREQUENCY OSCILLATOR (Audio Oscillator) A nonrotating device for producing an audio-frequency sinusoidal electric wave, whose frequency is determined by the characteristics of the device.

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BALANCED In communication practice, the term usually signifies: 1. electrically alike and symmetrical with respect to a common reference point, usually ground, OR 2. arranged to provide conjugacy between certain sets of terminals.

BAFFLE The panel upon which a loudspeaker is mounted, most commonly the front panel of an enclosure.

BASS BOOST An accentuation of the lower audio frequencies in the amplitude-frequency response of a system or transducer.

BASS REFLEX SPEAKER ENCLOSURE Type of extension loudspeaker cabinet frequently available as accessory item for tape recorders. Design employs a "port" or opening which greatly reinforces the bass, yet requires a relatively small cabinet.

BIAS An alternating current of high (beyond audibility) frequency, linearly added to the signal.

BIDIRECTIONAL MICROPHONE A microphone that picks up equally from two opposite directions. The angle of best rejection is 90 deg. from the front (or rear) of the microphone, that is directly at the sides.

BRIDGING The shunting of one signal circuit by one or more circuits usually for the purpose of driving one or more circuit branches.

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CARDIOID MICROPHONE An unidirectional microphone with moderately wide front pickup (131 deg.). Angle of best rejection is 180 deg. from the front of the microphone, that is, directly at the rear.

CARTRIDGE (Transducer) The element in a microphone that converts acoustical energy (sound) to electrical energy (the signal).

COMPRESSOR A transducer which, for a given input amplitude range, produces a smaller output range.

CONDENSOR MICROPHONE A microphone that generates an electrical signal when sound waves vary the spacing between two charged surfaces - the diaphragm and the backplate.

CROSSOVER NETWORK In multiple loudspeaker systems, a circuit employing electrical filters of frequency discriminating paths for routing high; low; and, in some elaborate systems, middle frequencies to the particular speakers designed to handle them.

CROSSTALK Undesired energy appearing in one signal path as a result of coupling from other signal paths.

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DECIBEL Abbreviated dB, it is a relative measure of sound intensity or volume. It expresses the ratio of one sound intensity to another. The dB is abut the smallest change in sound volume that the human ear can detect. Also used to express logarithmically voltage and power ratios. (A number used to express output sensitivity and sound pressure levels).

DISTORTION Any difference between the original sound and that reproduced by a recording machine. Distortion takes on many forms, and although it can never be completely eliminated, it can be reduced to a minimum in a good recording and reproducing system.

DISTORTION, HARMONIC Non-linear distortion of a system or transducer characterised by the appearance in the output of harmonics other than fundamental component when the input wave is sinusoidal.

DISTORTION, INTERMODULATION Non-linear distortion of a system or transducer characterised by the appearance in the output of frequencies equal to the sums and differences of integral multiples of the two or more component frequencies present in the input wave.

DISTORTION, PHASE DELAY Of a system or transducer, the difference between the phase delay at one frequency and the phase delay at a reference frequency.

DYNAMIC RANGE The difference, in decibels, between the overload level and the minimum acceptable signal level in a system or transducer.

DYNAMIC MICROPHONE High-quality electromagnetic-type pressure microphone which employs a moving coil in a magnetic field to convert sound pressure to electrical energy in a manner similar to that of an electric alternator or generator. Impedance and output are generally lower than those of the more common ceramic or crystal types. Low impedance permits the use of longer connecting cables.

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ECHO A wave which has been reflected or otherwise returned with sufficient magnitude and delay to be perceived in some manner as a wave distinct from that directly transmitted.

EQUALIZER The selective amplification or attenuation of certain frequency intervals to compensate for amplitude variations in an audio system. Also refers to recognised industry standards for recording and reproducing "characteristics", the proper use of which can assure uniform reproduction of prerecorded tapes and improvement of system signal-to-noise ratio.

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FEEDBACK (also ACOUSTIC FEEDBACK) The howling oscillation, or regeneration of sound caused by a system's microphonic pickup of the sound output from its own speakers. Negative electrical feedback in amplifier design is a singularly effective scheme used to improve stability and reduce distortion. In a PA system consisting of a microphone, amplifier, and loudspeaker, feedback is the ringing or howling sound caused by amplified sound from the loudspeaker entering the microphone and being re-amplified.

FIDELITY A measure of the degree of exactness with which sound is duplicated or reproduced.

FILTER (Wave Filter) A transducer for separating waves on the basis of their frequency.

FILTER, BAND-PASS A filter which has a single transmission band, neither of the cut-off frequencies being zero or infinite.

FILTER, HIGH-PASS A filter having a single transmission band extending from some cut-off frequency, not zero, up to infinite frequency.

FILTER, LOW-PASS A filter having a single transmission band extending from zero to some cut-off frequency, not infinite.

FILTER, SOUND EFFECTS A filter used to adjust the frequency response of a system for the purpose of achieving special aural effects.

FLAT RESPONSE A related but more definite term than simply Frequency Response. Implies a degree of excellence, but in order to be meaningful must be further defined in terms of dB variation from absolute flatness over a specified range (e.g. + 3db from 30 to 16,00 Hz.) An indication of a sound system's ability to reproduce all audible frequencies supplied to it, maintaining the original balance between low, middle, and high frequencies.

FREQUENCY (also TONE) The repetition rate of cyclic energy such as sound or alternating electrical current, expressed in Hertz (1 Hz = 1 cycle per second).

FREQUENCY RANGE The range between the highest and lowest pitched sounds which a tape recorder or other sound system component can reproduce at a usable output or volume level.

FREQUENCY RESPONSE A terms closely related to but more specific than Frequency Range. Calls for output versus frequency data over specified frequency range, usually in the form of a chart for transducers like microphones and speakers. Most commonly expressed for tape recorders as given in the example for Flat Response. A graph showing how a microphone responds to various sound frequencies. It is a plot of electrical output (in decibels) vs. frequency (in Hertz).

FREQUENCY RESPONSE TAILORING SWITCH A switch on a microphone that affects the tone quality reproduced by the microphone. (Similar to a bass or treble control on a hi-fi receiver).

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GAIN The voltage ratio of the output level to the input level for a system or component of a system. Usually in terms of dB.

GAIN CONTROL A device for adjusting the gain of a system or transducer.

GAUSS A measure of flux density, numerically equivalent to flux lines or Maxwell's per square centimetre.

GROUND A point in an electrical circuit used as the zero voltage reference and which is connected to the earth or a part of the circuit serving as earth.

GROUND LOOP The path in a ground circuit between two or more points intended to be at the same voltage (zero), but which are not because of ground resistance. It can result in hum and other undesirable disturbances in circuits where signal strength is low.

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HARMONIC DISTORTION Distortion characterised by the appearance in the output of harmonics of the fundamental frequency when the input wave is sinusoidal. Usually expressed in per cent, numerically equal to one hundred times the ratio of the root-means-square voltages of each of the individual harmonic frequencies, to the root-mean-square voltage of the fundamental.

HARMONICS Overtones which are integral multiples of the fundamental frequency.

HERTZ (abbreviated Hz) A unit measuring frequency and equal to one cycle per second.

HISS Audio-frequency noise having subjective characteristics analogous to prolonged sibilant sounds.

HUM (Power Supply Hum) Interference from a power system characterised by the presence of undesired energy at power supply frequency or harmonics thereof.

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IMPEDANCE In an electrical circuit, opposition to alternating current, measured in ohms. A high impedance microphone has an impedance of 30,000 ohms or higher. A low impedance microphone has an impedance of 38 to 300 ohms. High impedance microphones should be connected to high impedance inputs and low impedance microphones should be connected to low impedance inputs except when an impedance matching transformer is used. The resistance to the flow of alternating current in an electr5ical circuit, generally categorised as either high or low, but sometimes given in ohms or millions of ohms (megohms). Commonly used to characterise the input or output termination of components so that proper match can be made when interconnecting two or more devices.

IMPEDANCE, LOAD The impedance presented by the load.

INSERTION LOSS The ratio of the power delivered to that part of a transmission system which will follow a transducer, to the power delivered to that same part of the system after the insertion of the transducer.

INPUT SIGNAL An electrical voltage presented to the input of an amplifier, head, or other electronic component.

INTERMODULATION DISTORTION Distortion which results when two or more pure tones are nonlinearly combined to produce new tones with frequencies representing the sums and differences of the original tones and their harmonics.

ISOLATION

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kHz Abbreviation for kilohertz (Thousands of cycles per second).

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LEAKAGE Pickup of an instrument by a microphone intended to pick up another instrument. Creative leakage is artistically favourable leakage that adds a "loose", "live" feel to a recording.

LOAD 1. A device which receives power. 2. The power delivered to such a device.

LOUDNESS Sound level as detected by the average human ear. The ear is more sensitive to middle frequencies than to low or high extremes, especially at low levels.

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MICROPHONE A sound transducer or device for converting sound waves into electrical energy of the same frequency.

MICROPHONICS The noise caused by mechanical shock or vibration of elements in a system.

MIXER Device by which signals from two or more sources can be blended and fed simultaneously into power amplifier at the proper level and balance.

MOTORBOATING An undesired oscillation in an amplifying system or transducer, usually of a pulse type, occurring at a subaudio or low audio frequency.

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NETWORK A combination of elements.

NOISE, AUDIO-FREQUENCY Any unwanted disturbance in the audio-frequency range.

NOISE LEVEL 1. The noise power density spectrum in the frequency range on interest, 2. The average noise power in the frequency range of interest, or 3. The indication on a specified instrument

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OCTAVE In communication, the interval between two frequencies having a ratio of 2:1

OMNIDIRECTIONAL MICROPHONE A microphone that picks up sound equally well from all directions.

OUTPUT POWER The power delivered by a system or transducer to its load.

OVERLOAD LEVEL Of a system or component, is that level above which operation ceases to be satisfactory as a result of signal distortion, overheating or damage.

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PAD A non-adjustable passive network which reduces the power level of a signal without introducing appreciable distortion.

PA. SOURCE That which supplies signal power to a transducer.

PEAK LIMITER A device which automatically limits the magnitude of its output signal to approximate a preset maximum value by reducing its amplification when the instantaneous signal magnitude exceeds a preset value.

POLAR PATTERN (DIRECTIONAL PATTERN,POLAR RESPONSE) A graph showing how the sensitivity of a microphone varies with the angle of the sound source, at a particular frequency. Examples of polar patterns are unidirectional and omnidirectional.

POP A thump of explosive breath sound produced when a puff of air from the mouth strikes the microphone diaphragm. Occurs most often with "p", "t' and "b" sounds.

POP FILTER An acoustically transparent shield around a microphone cartridge that reduces popping sound. Usually a ball-shaped grille.

PREAMPLIFIER An amplifier connected to a low-level signal source to present suitable input and output impedances and provide gain so that the signal may be further processed without appreciable degradation in the signal-to-noise ratio.

PRESENCE PEAK An increase in microphone output in the "presence" frequency range of 2,000 Hz to 10,000 Hz. A presence peak increases clarity, articulation, apparent closeness, and "punch".

PROXIMITY EFFECT The increase in bass occurring with most cardioid microphones when they are placed close to an instrument or vocalist (within 6 inches). Does not occur with omnidirectional microphones.

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REFERENCE VOLUME The volume which gives a reading of 0vu on a standard volume indicator.

ROLL-OFF A gradually increasing loss or attenuation with increase or decrease of frequency beyond the substantially flat portion of the amplitude-frequency response characteristic of a system of transducer.

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SENSITIVITY The electrical output that a microphone produces for a given sound pressure level.

SINGLE-ENDED PUSH-PULL AMPLIFIER CIRCUIT An amplifier circuit having two transmission paths designed to operate in a complementary manner and connected so as to provide a single unbalanced output without the use of an output transformer.

SOUND CHAIN The series o f interconnected audio equipment used for recording or

SUBHARMONIC A sinusoidal quantity having a frequency which is an integral submultiple of the fundamental frequency of a periodic quantity from which it is derived.

SEPARATION The degree in which two stereo signals are kept apart. Stereo realism is dependent on the successful prevention of their mixture before reaching the output terminals of the power amplifier.

SIGNAL-TO-NOISE RATIO The voltage ratio, usually in dB, between the loudest undistorted tone recorded and reproduced by a recorder, and the noise re-produced when the signal (but not the bias) is reduced to zero.

STEREOPHONIC SOUND Dimensional or directional sound reproduction achieved through the use of two or more sound tracks, or channels, heard simultaneously through loudspeakers arranged in the same relative positions as were the microphones during recording.

SUPERCARDIOID MICROPHONE A unidirectional microphone with tighter front pickup than a cardioid (115 deg.), but with some rear pickup. Angle of best rejection is 126 deg. from the front of the microphone, that is 54 deg. from the rear.

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THUMP A low-frequency transient disturbance in a system or transducer characterised audibly by the onomatopoeic connotation of the word.

TRANSDUCER A device capable of being actuated by signals from one or more systems or media and of supplying related signals to one or more other systems or media. It converts one form of energy to another. A microphone transducer (cartridge) converts acoustical energy (sound) to electrical energy (the signal).

TRANSFORMER, LINE A transformer connecting a transmission line to terminal equipment used for such purposes as isolation, line balance, impedance matching, or additional circuit connections.

TREBLE BOOST An accentuation of the higher audio frequencies in amplitude-frequency response of a system or transducer.

TWEETER A loudspeaker designed to reproduce only the treble or high frequencies of the audible spectrum.

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UNBALANCED Not balanced.

UNIDIRECTIONAL MICROPHONE A microphone that is most sensitive to sound coming from a single direction - in front of the microphone. A cardioid microphone is an example of a unidirectional microphone.

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VOLUME In an electric circuit, the magnitude of a complex audio-frequency wave as measured on a standard volume indicator. Note 1: Volume is expressed in v. Note 2: The term volume is used loosely to signify either the intensity of a sound or the magnitude of an audio-frequency wave.

VU The unit of volume in which the standard volume indicator is calibrated.

VU METER A volume unit meter which indicates audio-frequency power levels in decibels relative to a fixed reference level. The meter movement differs from those of ordinary voltmeters in that it has a specified ballistic response adapted to monitoring speech and music.