Attenuate - To reduce the level (volume, loudness, energy) of an acoustical (or electrical) signal.

ASTM E 84 - A test method for determining the surface burning characteristics of building materials, sometimes referred to as the “Steiner tunnel test”. This test method is for single products and evaluates both flame spread and smoke development, assigning different classes based upon test results:

Articulation
- A measure of the intelligibility of speech.

Area Effect

Analog - Analog representations of sound replicate its waveform, while transferring it through different media. All sound is analog. Audio may be analog or digital.

Ambient noise - All pervasive noise associated with a given environment.

Ambience - The residual “room sound” of a listening environment.

Acoustical tile - A porous architectural material, usually constructed from fiberglass or pressed board, which is most absorptive at the high frequencies.

Absorption coefficient - Ratio of sound absorbing effectiveness, at a specific frequency, of a unit area of acoustical absorbent to a unit area of perfectly absorptive material. The portion of energy absorbed when a sound wave strikes a material. The absorption coefficient of a material is dependent on the frequency of the sound wave.

The opposite of reflection. Sound absorption results from the conversion of sound energy into another form, usually heat or motion, when passing through an acoustical medium. When a sound wave encounters resistance, absorption occurs. Absorption is measured in sabins (after Wallace Clement Sabine). One sabin is the amount of absorption offered by one square foot of open air