acceptable/normal speech privacy: according to the recently updated standard for Speech Privacy in Open Offices, (American Standard Test Method (ASTM) E1130–02) the speech privacy of a space is “acceptable” or “normal” (meaning not-readily understood) when the AI is under .20 or the SPI is over 80%

acoustics: the study of sound.

AI (articulation index): a quantitative measurement of the intelligibility of speech in a given location; an articulation index of 1 means that all speech can be understood, 0 means that no speech can be understood.

ASTM: American Standard Test Method (ASTM) E1130–02

band: also called “frequency band”, a band is a specific range of frequencies.

bandwidth: the difference between the highest and lowest frequencies in a band.

CAT-3: Category 3, a standardized multi-conductor type of structured data cable.

confidential speech privacy: The standard measurement for this defines the AI as under .05 or the SPI as over 95% (ASTM E1130—02).

control module: the unit that generates the sound masking signal and that controls the output of the system.

dB (decibel): The decibel (dB) is a logarithmic measure of the ratio between two quantities, often used in measurements of the loudness of sound.

dBA: (A-weighted decibel) the A-weighted decibel is one of four frequency weightings (the others are C-, B- & Z-) used to allow the result of an acoustical measurement to be expressed as a single number. The weightings are also intended to approximate the responses of the ear to different frequencies at different levels. An A-weighting is the most relevant to sound masking system loudness.

direct field: the sound field from loudspeakers installed directly in the ceiling thus eliminating the need for the sound to penetrate the ceiling tile.

emitter: a loudspeaker.

Hz (Hertz): the notation of frequency (cycles per unit of time); 1 Hz means that an event repeats once per second.

masking system generation: A Cambridge Sound Management nomenclature used to categorize the advancements of sound masking technology. Systems in the first generation (developed circa 1965) are characterized by their use of plenum-based loudspeakers (demanding acoustical consideration of heating ducts, piping, electrical components, etc.) controlled by a bulky “head end” controller. The loudspeakers required significant systems design and complex post-installation measurements and adjustments by acoustical experts. In addition, the masking sound would overflow to spaces, such as private offices, where sound masking was not desired.

Second generation systems (developed circa 1975) changed the design of the loudspeakers to combine them with integrated electronics. Early designs of this equipment required installers to go up into the plenum to tune each speaker. Subsequent designs eliminated this inconvenience with programmable loudspeakers from head-end equipment, and daisy chained loudspeakers but did not eliminate the complexities of design, the overflow problem or the need for costly post-installation adjustments.

In third, and most recent, generation systems loudspeakers are no longer in the plenum, but emit directly into the desired coverage area; there are no spectral adjustments needed subsequent to installation, and the energy required is under 10 watts for up to 300,000 square feet of coverage (roughly that of a nightlight) opposed to 100 times that for first generation systems.

octave bands: octaves are standardized ranges of frequency. As each successive octave increases, the center frequency and frequency range it defines doubles. Graphed against octaves, pink noise is flat meaning there is equal sound energy in each. Acousticians, therefore, often use pink noise as a reference signal for measurements.

open office plan: a common configuration of large office spaces without walls that usually involves cubicles.

pink noise/white noise: Pink noise is noise with a decreasing amount of energy per Hz with higher frequency. White noise is inaccurately, but commonly used to describe any constant, low-level background noise, however, noise is classified as "white" if it has a flat spectrum or energy per Hz over all audible frequencies. Qt Quiet TechnologyTM does not emit either a precisely “white” or precisely “pink” noise spectrum, as neither would effectively solve the problem. Pink noise sounds less unpleasant than white noise, but is still “hissy.” Qt Quiet TechnologyTM instead uses a combination of the two spectra; one which emulates the spectrum of human speech frequencies. (see graph of Pink an White Noise, and speech).