Audio Terminology And Definitions Dictionary

 

PAL  PAL, or Phase Alternate Line, is the dominant global format for analog television broadcasting and video display. It is based on 625-line frames broadcast at 50 fields, or 25 frames per second, based on the 50 Hz AC supply in the countries that have adapted the system. As with NTSC broadcasts, the signal is interlaced into two fields of 312 lines each. Note: Brazil uses a variant of PAL (PAL-M) that uses 525 lines at 60 Hz.

 

Pan  In this case, a "pan" refers to a sound that moves from one speaker to another. Examples include the sound of a car as it races across the screen from left to right or a helicopter that suddenly flies into the center of the action from behind you.

 

Parallel/Series  All electrical components can be connected in series or in parallel. Their effect on signal may reverse depending on the type of connection. An inductor connected in series with a woofer will provide a simple low pass filter. A capacitor connected in series with a tweeter will provide a high pass filter. An inductor connected in parallel with a series capacitor will help create a 12dB/octave high pass filter for a tweeter. A capacitor connected in parallel with a series inductor will help create a 12dB/octave low pass filter for a woofer. Band pass filters can be created by means of a series capacitor and series inductor, or by a mixture of series and parallel capacitors and inductors. 

 

Passive  A component unconnected electrically to the signal source, such as an Auxiliary Bass Radiator. Or a component unconnected to a source of mains power, such as a passive pre-amplifier which acts purely as a source signal switching/routing device providing control functions for a power amplifier.

 

Parametric Equalizer  An equalizer with several user-accessed adjustments (usually amplitude and "Q," or the range of frequencies affected by one control).

 

Passive Radiator   In a loudspeaker, a diaphragm without a "motor" attached to it (hence "passive"). The speaker responds to pressure from inside the enclosure in such a way as to augment the system's bass response.

 

PCB   Printed Circuit Board.

 

PCM (Pulse Code Modulation)  Often called "multi-bit." A digital data structure composed of "words" made up of a (generally even) number of individual bits (either "0s" or "1s"). PCM completely defines the amplitude or strength of the sample it represents. Words follow each other at a very high rate, called the "sampling frequency." For example, the PCM data structure used by the CD is often referred to as 16/44.1.This means that each word is composed of 16 bits and that words follow each other at the rate of 44,100 per second (or 44.1 kHz). The most common PCM data structure for DVDs is 24/96, or 24-bit words at the rate of 96,000 per second (or 96 kHz).

 

Peak Output   Sudden bursts of power are required in response to certain types of music. Loud drum beats and percussive piano playing demands a high peak output power from an amplifier. Failure to do so causes signal compression, resulting in a squashed thick sound as if the drum sticks or piano hammers are made of sponge. 

 

Pentode  Commonly used valve type. Contains cathode, anode, grid and two further electrodes. 

 

Phase  The relative timing of two or more signals. Signals reproduced in time with each other are said to be "in phase" while signals reproduced out of sync with each other are said to be "out of phase" to one degree or another. Properly "phased" loudspeakers, where each loudspeaker system in an audio/video system emits a positive pulse when the amplifier delivers one, are necessary for proper spatial reproduction of music or movie soundtracks. In addition, phase is central to understanding how a matrix works.

 

Phonostage  The extra equalization and gain stage required to amplify signal from a pickup cartridge to line level. The RIAA equalization is necessary because bass signals are compressed to allow them to be cut onto vinyl records. There would be insufficient space otherwise. Moving magnet cartridges, which typically deliver output in mV (for 5cm/sec standard acceleration) require less amplification than most moving coil cartridges which deliver output typically in uV for the same acceleration standard.

 

Pilot Tone   The 19 kHz tone carrier tone on which stereo sum and difference signals are broadcast. It is removed by the stereo decoder of FM tuners. 

 

Pink Noise    A type of equalized random noise that contains equal amounts of energy in each of the ten audible octaves. Extensively used in audio testing, it resembles the energy distribution found in music.

 

Pixel A common informal term for "picture element." A pixel is the single smallest point on a screen or chip surface that is used to construct a video image. Pixels are arranged in rows and columns in order to produce a complete image.

 

Pixel Density Pixel density is the actual number of physical picture elements on a screen surface or an LCD/DLP projection chip. LCD and plasma screens as well as LCD/DLP projectors are called "fixed pixel" devices for this reason. The higher the pixel count, the higher the resolution capability of the video display device. Pixel density is sometimes referred to as a device's "native resolution." A pixel count of 1024 x 768 (1,024 pixels across by 768 pixels down, for a total of 786,432 pixels) is sufficient for DVD. However, 720p HDTV signals need a display with 921,600 pixels (1260 x 720) to show the signal's full resolution. A 1080i or 1080p signal for sources such as HDTV broadcasts and Blu-ray discs needs a native pixel count of 2,073,600 (1920 x 1080) for a one-to-one representation of the 1080i or 1080p signal.

 

Planar Driver A generic term for a comparatively large, flat driver that most often is as large as the height and width of the speaker itself. Planar drivers, when properly excited by an amplifier's signal, move air equally well from all points—front and rear—on their surface. (Dynamic drivers, in contrast, are small, radiate in only one direction, and are the only active elements on a speaker's baffle.)

 

Plasma Display  A plasma TV display is one type of "flat panel" technology. Plasma displays consist of very small cells, each containing two glass panels separated by a narrow gap in which neon-xenon gas is injected and sealed in plasma form. The gas is electrically charged at specific intervals to strike red, green, and blue phosphors in order to create an image. Each red, green, and blue phosphor element is called a sub-pixel. Combined, they form a pixel.

 

Polarity  The difference between positive and negative.

 

Polypropylene/Polystyrene Capacitors  These very  high-quality components are usually employed in the signal path where large-value capacitors are not required. Their advantage is that they have a very small "Miller Effect," or memory, compared to electrolytic capacitors. This means that each subsequent signal passing through them has greatly reduced coloration, resulting in better fidelity.

 

Port  An opening in a speaker enclosure that allows the back wave from a woofer to exit the cabinet and reinforce the woofer's front wave. (See also: bass reflex and vent.)  

 

Potentiometer   The device used to provide volume level setting. Ideally a potentiometer is a variable resistor. Often shortened colloquially to 'pot'.

 

Power Amplifier     An electronic circuit or component that increases the level of signal from a source or preamplifier until it is able to drive a loudspeaker.

 

Power Handling   A loudspeaker's ability to dissipate heat so that input from an amplifier does not damage the voice coils. Though typically specified in watts, there is no industry-wide standard for this specification.

 

Power Output   The amount of power, usually measured in watts per channel, delivered by a power amplifier or integrated amplifier to loudspeakers. The rated maximum rms or continuous sine wave power output is a less relevant indicator of the dynamic range capability of an amplifier than its peak output power capability or its peak current delivery measured in Amps. Amplifier power output is usually specified relative to an 8 Ohm resistive load. However the majority of loudspeakers present a load that varies according to audio frequency, rising at loudspeaker drive unit resonant frequency but often decreasing elsewhere across the bandwidth. Impedances lower than 4 Ohms require an amplifier to have considerable current drive capacity.

 

Power Response    A little understood but nonetheless important specification that defines the total radiated acoustic output of a loudspeaker. Power response is measured at several angles in the far (random-phase, or reverberant) field. It is a better indication of "real world" loudspeaker performance than more-common anechoic measurements.

 

Power Supply   Electronic components deriving their power from a mains source require a transformer, smoothing capacitors and rectifier to turn the mains AC into a stable DC rail voltage. Amplifiers in particular are heavily dependent on a stable rail voltage. However components as varied as CD players, DACs and turntables also benefit from well configured power supplies often as separate items. Power supplies can be a useful retrofit upgrade. 

 

Preamplifier An audio/video system's switching center, a preamplifier allows the user to choose a particular source component (CD or tuner, for example) and to adjust tonal quality and system volume.

 

Presence Band  The middle range of audio frequencies to which the ear is most sensitive. Typically taken to mean the 1-4kHz frequency range.

 

Precedence Effect  A phenomenon of human hearing that describes how we judge the origin of a sound coming from more than one direction by the location from which we first hear that sound. For example, if a car on your left honks its horn, the sound reaches your left ear before it reaches your right ear. Using this information, your brain concludes that the car is on your left. (Also known as the Haas Effect.)

 

Printed Circuit Board  (Abbr: pcb).  The board onto which a conducting track and solid state components - resistors, capacitors and the like - are mounted. pcbs may be single sided or double sided, fitted vertically or horizontally. 

 

Progressive Scan Progressive scan devices show an image by scanning in sequential order each line (or row of pixels) that make up a frame. In other words, in progressive scan, the image lines (or pixel rows) are scanned in numerical order (1,2,3) down the screen from top to bottom, instead of in an alternate order (lines or rows 1,3,5, etc., followed by lines or rows 2,4,6) as in interlaced scanning. Progressive scanning presents a smooth, detailed image that is virtually immune to a phenomenon called "interlace flicker."

 

Psycho-Acoustics  The overlapping branches of acoustics and psychology where research is conducted into human perception of sound.

 

PWM   Pulse Width Modulation. A form of digital recording which makes use of the width of a digital pulse.