Glossary – P
A network of resistors designed to introduce a fixed loss, or for impedance-matching purposes.
To shift a sound image as desired between the positions occupied by the loudspeakers in stereo or quadraphonic reproduction.
(Panoramic potentiometer.) Ganged volume control used in panning.
The output from spot microphones is mixed into the two stereo channels in proportion to their position. This produces amplitude but not phase differences. The stereo image is thus imperfect.
A light, rigid structure which reflects sounds to a focus at which a microphone is placed.
Frequency correction device which allows both the frequency and the bandwidth of the boost or cut to be selected.
Any one of the various frequencies contained in a complex wave form that corresponds to a musical tone.
Unit of pressure. Equals l Newton per square meter.
The band of frequencies that are not attenuated by a filter.
A network or circuit containing only passive components, such as resistors, capacitors and inductors.
To connect reserve equipment by means of flexible cords and plugs, so that the connections to the normal equipment are automatically broken by break-jacks.
A shielded cable utilized to connect one audio device to another.
Any socket in a jack bay.
The total point-to-point distance between a sound source and the listener.
An instrument designed to measure the volume of program in a sound channel in terms of the peaks averaged over a specified period.
The maximum absolute value of instantaneous sound pressure for any specified time interval. The most common unit is the microbar.
Of a varying quantity in a specific time interval. The maximum numerical value attained whether positive or negative.
The instantaneous high level transients of an audio signal.
A moving-conductor speaker in which the steady magnetic field is produced by a permanent magnet.
Abbreviation for picofarad.
An L + R signal formed in a mixer, used to drive a "hole-in-the-middle" speaker.
Method of sending DC supply to a capacitor microphone by connecting the positive side to both signal wires of a balanced line and the negative to the screen.
Position occupied at any instant in its cycle by a periodic wave; a part of a sound wave or signal with respect to its passage in time. One signal is said to be in phase with, or to lead, or to lag, another reference signal.
The attenuation that occurs when two waveforms of equal frequency and opposite polarity are combined. The attenuation may be total when the waveforms are also of equal amplitude.
Form of distortion in which wave-trains of different audio frequencies travel with different group velocities, owing to the characteristics of the medium (e.g. a landline).
An amplifier that provides an output which is 180 degrees out of phase with its input, or an amplifier that provides a pair of output voltages which are also 180 degrees out of phase with each other.
The displacement of a waveform in time. Some electrical components introduce phase shift into a signal, and the shift is of the same angle for all frequencies. This means that each frequency is displaced differently and distortion occurs. Electrical cancellation may occur when two equal signals are out of phase by 180 degrees.
The phase shift introduced by a crossover network.
The phase shift introduced in a signal path by the insertion of equalization.
The unit for measurement of the apparent (subjective) loudness level of a sound. At 1,000 Hz, the phon rating corresponds to the measured sound level. At all other frequencies, a sound level which - to the listener - seems to be of the same loudness as the 1,000 Hz tone, is given the same phon rating, regardless of the actual measured sound level.Phase shift, equalizer -- The phase shift introduced in a signal path by the insertion of equalization.
1. Sound effect obtained by splitting a signal to two tape machines or networks and introducing a time delay in one of them. Originally achieved by running the same signal on two recorders, one of which was intermittently slowed by an obstruction held against the tape spool. When combined there were alternate cancellations and reinforcements of the two signals. 2. A variable comb filter effect, created by mixing a direct signal with the same signal, passed through a phase shift network.
A device used with a turntable to convert mechanical variations into electrical impulses. There is a variety of ways whereby the motion of the stylus can be translated into an electrical signal. Most of these are grouped into the class known as magnetic, because they produce relative movement between a coil and magnetic field. They are velocity devices because the magnitude of the induced signal depends on the velocity of the stylus movement rather than its amplitude. But as tracing speed increases with amplitude so does the output signal. However, stylus velocity also increases with frequency, giving a rising treble response. This is the opposite of the recording cutter characteristic, but as that was modified by the RIAA curve, so also inversely must the response of the magnetic cartridge. At present the moving-magnet and moving-coil types are most in favour, but other types as well as non-magnetic varieties are in use.
The function of carrying the cartridge across the disc is complex. Lateral tracking error must be minimized by optimum offset angle and overhang. Various methods have been used to avoid tracking errors.
The principle is similar to that of the moving-magnet except that a stationary magnet induces a field into an armature which is moved by the cantilever. It was a useful alternative when a magnet could add appreciable mass to the cantilever. Lightweight magnetic materials have now overcome this snag, so the induced magnet is less attractive.
Two slices ofpiezo-electric materials such as barium titinate or lead zirconate titinate are set at angles, and stressed by stylus movement so producing a voltage. Output is proportional to the amplitude rather than velocity of the recording signal and is thus the approximate inverse of the RIAA recording characteristic. No equalisation is therefore required. A load of not less than 1 M~ is needed, lower values causing loss of bass. If used into a magnetic input socket with a 47 kOhm load, the RIAA equalisation will roughly compensate for the bass loss.
A pair of tiny coils are mounted so that they can rock about an axis between the pole pieces of a magnet. Each responds only to one plane of stylus movement. To minimize mass, the coils have few turns and so are low impedance and give low output; they thus need special pre-amps or transformers. Some have been produced using many turns of very fine wire, thereby giving higher impedance and output.
An armature actuated by the stylus, passes through the centre of a coil which is enclosed between the poles of a permanent magnet. Movement of the armature disturbs the magnetic field through the coil. All the early mono pickups used this principle.
Reluctance here is the resistance to a magnetic field offered by an air gap. One pole piece of a magnet is split through a pair of coils to twin faces, in proximity to which is a ferrous moving member linked to the stylus and connected to the other pole. Movement varies the air gap between the member and one face, hence also the magnetic flux through the circuit and coil.
The stylus cantilever is joined to the free end of a lightweight cylindrical magnet made of material such as samarium cobalt. It is pivoted at the far end, and surrounded by four yoke pieces spaced at 90 degree intervals. Each opposite pair of yokes forms a magnetic circuit through one of two coils. Movement of the magnet in one direction induces a field in the appropriate pair of yokes and from there to the coil.
A speaker that employs a piezoelectric substance as a driver or motor.
A unit equal to 1 micromicrofarad.
A capstan idler.
A signal wave, usually a single frequency, transmitted over the system to indicate or control its characteristics.
1. That attribute of auditory sensation in terms of which sound may be ordered on a scale related primarily to frequency. 2. Number of grooves per inch.
Random noise signal having the same amount of energy in each octave. Therefore, the amount of energy between 100 Hz and 200 Hz, a 100-cycle-wide segment, is the same as the energy between 10 kHz and 20 kHz.
A graph of a transducer's directional sensitivity, measured over a 3600 circumference drawn around the transducer. See Polar Pattern, Loudspeaker, and Polar Pattern, Microphone.
A wave in which successive wavefronts are parallel planes.
A uni-directional polar pattern, with the axis of minimum sensitivity at 180 degrees. The pattern is so-called because of its characteristic shape.
A polar pattern with axes of maximum sensitivity at 00 and 180 degrees, and minimum sensitivity at 90 degrees and 270 degrees.
A uni-directional polar pattern, slightly narrower than a regular cardioid pattern, and with a lobe in the rear.
A bi-directional polar pattern, so-called because of its characteristic shape.
A graph of a microphone's relative output level for sound sources originating at various points on a 360 degrees circumference drawn around the transducer.
A graph of a loudspeaker's measured output level at various points on a 360 degrees circumference drawn around the speaker.
A uni-directional polar pattern, slightly narrower than a regular cardioid pattern, with a lobe in the rear that is somewhat wider than the one on a hypercardioid pattern. The axes of minimum sensitivity are at about 125 degrees and 235 degrees.
A circular polar pattern, indicating equal sensitivity (or measured output level) at all angles on a 360 degrees circumference drawn around the transducer.
A plot of the variation in radiated energy with angle relative to the axis of the radiator. Similarly used for receivers and microphones.
A polar pattern of a microphone that is most sensitive to sounds originating directly in front of it.
The charging voltage applied to the capacitor/diaphragm of a condenser (capacitor) microphone.
Referring to the positive or negative direction of an electrical or magnetic force.
A wind screen.
A plastic film, used as a base material in the production of magnetic recording tape.
Openings to the rear and side of a uni-directional microphone, allowing sound waves to reach the rear of the diaphragm.
An opening in the front baffle of a loudspeaker cabinet.
Recording of music, effects or dialogue to synchronize with a previously filmed picture.
Rate of flow of energy, developed by an acoustical or electrical system.
Potential divider or variable attenuator used, for example, to control the volume of a program.
The electrical energy produced or dissipated in a circuit.
The sound energy produced by a sound source.
A circuit supplying d.c. power to a condenser (capacitor) microphone.
A circuit supplying d.c. power to an amplifier or other electronic system.
The undesired transfer of a recorded signal from one groove to another. N.B. Post-echo can also occur.
A circuit that supplies d.c. powering to condenser microphones, using the same conductors as the audio signal.
A system of complementary filtering at the recording and reproducing stages which serves to improve the overall signal-to-noise ratio and reduce breathing and other audible unpleasant consequences of location recording and noise reduction.
A deliberate change in the frequency response of a recording system for the purpose of improvement in signal-to-noise ratio, or the reduction of distortion (see also De-emphasis).
Listening to a program before it is faded up for transmission or recording; technical facilities provided for this purpose.
Device that boosts extremely weak signal voltages, such as those from microphones or mag heads, to a level that is usable by power amplifiers, and at the same time accomplishes the necessary equalization for industry standards.
Molding of thermoplastic material produced from the stamper by the application of heat and pressure and subsequent cooling. Two stampers, one for each side of the disc, are steam heated in the press as the pressure is applied to the plastic material, which is then cooled before removal. Too short a heating/cooling cycle can cause minute discontinuities and pits. On removal, the flash is trimmed from the pressing which is then labeled and sleeved. The next step is Testing.
Degree of forwardness in a voice or instrument achieved by boosting in the frequency region 2-8 kHz.
The acoustic pressure, expressed in decibels. The sound pressure level at the threshold of hearing is O dB SPL.
Method of responding to sound signals in which the sound wave has access to both sides of a microphone diaphragm.
The acoustic pressure of a sound wave. The sound pressure at the threshold of hearing is 2 x 10-5 newtons/m2
Method of responding to sound signals in which the sound wave has access to only one side of a microphone diaphragm.
An equalized or otherwise modified copy of the original master for production purposes.
The undesired transfer of recorded signal from one layer to another of the recording medium when these layers are stored on spools.
Increase in low frequency response which occurs at distances less than about 1 meter from pressure gradient operated microphones.
A copy of a master tape, generally filed as a protection against the damage or loss of the master tape.
Arrangements of microphones, amplifiers and loudspeakers used to reinforce speech or music over a large audience area.
The study of the brain's perception of, and reaction to, all aspects of sound. (i.e., intensity, time of arrival differences, reverberation', et al.)
The practice of recording a track, or tracks, in small segments, say one phrase at a time. So-called because the engineer spends so much time "punching" the record button.
Modulation in accordance with a pulse code.
A single frequency sine wave, with no harmonics present.
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