Audio Terminology And Definitions Dictionary

 

R  Symbol for resistance or resistor.

 

Reactance  A frequency selective resistance. Inductance and capacitance are the two forms of reactance. The combination of resistance and  reactance is impedance.

 

Radiation Pattern   The area over which a loudspeaker radiates most of its energy and the evenness with which this energy is distributed within that area. Speakers may be omnidirectional and radiate freely in all directions or directional with specifically designed radiation patterns. Directional speakers can be broken down further into three main groups: direct radiators (energy distributed primarily to the front of the speaker), bipolar (equal energy radiation to the front and rear of the enclosure with matching polarity), and dipolar (equal energy radiation to the front and rear of the enclosure but phased differently).

 

Rainbow Effect     An artifact of single-chip DLP display devices that results from the interaction between the light source, the color wheel needed in a single-chip device, and the chip itself. The "rainbow effect" presents itself as brief color flashes when the viewer looks rapidly from side to side on the screen or from the screen to a point in a room. Fortunately, not everyone is sensitive to rainbow effects.

 

RAW  An image file of minimally processed data received from a digital camera. Most camera manufacturers have their own proprietary version of the RAW image format and their own file suffixes. Canon, for example, uses .crw or .cr2 for their version of RAW. Nikon's RAW files end in .nef, while Sony uses .arw and .srf suffixes. Professionals prefer shooting in RAW because the additional information these large files contain allows greater flexibility in post-production editing. Because the image is basically unprocessed (as compared to a JPEG image), RAW files can retain very subtle color variations and fine detail. Color changes, contrast adjustments, and other manipulations of a RAW image yield significantly fewer digital artifacts than the same changes made to a comparable JPEG file.

 

RealMedia     One of the most popular formats for streaming content on the Internet, RealMedia includes the RealAudio codec for sound clips and RealVideo codec for movies. RealAudio and RealVideo files are often given the common RealMedia.rm file extension. RealMedia is a container format that's often heavily compressed for streaming over dial-up Internet connections. RealMedia variable bitrate (RMVB) has been developed for VBR streaming files.

 

Receiver  An audio or audio/video component that combines a tuner, preamplifier, and power amplifier in a single chassis.

 

Rectification  An essential process in the conversion of AC to DC by means of a half wave rectifier, a form of diode which is a key element in a power supply.

 

Resistance   Pure resistance is measured in Ohms. Resistance in the form of resistors blocks the flow of electric current in a linear or non frequency selective  manner.

 

Resonance    The characteristic of a physical object that causes it to vibrate when excited by an external force and, once excited, to keep vibrating after the original stimulus ceases. Examples of resonance include a tuning fork and a bell. An unwanted resonance, particularly in a loudspeaker enclosure, can color the output of the entire loudspeaker system by introducing frequencies that are unrelated to the original signal. Rooms and loudspeakers are resonant systems.

 

Reverberation Time  The time it takes for a sound generated in a room to drop to 60dB below its original level. It is a measure of the size and reflectivity of the room boundary surfaces. A typical listening room measuring about 2.5 x 6.5 x 3.75 meters (HxLxW) will have a Reverberation Time of about 0.4 seconds. Major concert halls have a far longer RT in the region of 1.5 to 2.5 seconds.

 

RF   Radio Frequency. Typically frequencies upwards of 70kHz through to MHz.

 

RFI   Radio Frequency Interference. The disruption of radio signal reception caused by any source which generates radio waves at the same frequency and along the same path as the desired wave.

 

RIAA  Record Industry Association of America. It is the RIAA disc equalization curves that are almost universally followed by record companies making LPs, and by hardware manufacturers configuring their phono amplifiers.

 

Roll Off A gradual attenuation (either intentional or unintentional) of a signal, usually above or below a given frequency known as the "corner frequency."

 

rms  Root Mean Square. rms qualifies an amplifier power output specification to signify continuous power  output as opposed to peak or transient power.

 

Rumble   Turntable rumble is a very low frequency noise caused usually by main bearing noise. It is usually a sign of poor bearing lubrication.