Longitudinal wave - A wave in which vibrations are in the direction of propagation of sound as are sound Wavesin air.

Live - A reverberant acoustical condition, usually used in reference to a room whose many reflective surfaces encourage a lengthy reverberation time.

LEDE - Live end, dead end. An optimal acoustical treatment plan for rooms in which one end is highly absorbent and the other end reflective and diffusive.

Leakage - Any unwanted sound picked up by (or “leaking” into) a microphone from another instrument or loudspeaker. Sound from one room that is heard in another.

Law of the first wavefront - The first wavefront falling on the ear determines the perceived direction of the sound.

Late reflection - Reflected energy that occurs a greater distance away from the source than an early reflection. Sometimes referred to as “slap-back” or echo.

Kilohertz / kHz - 1,000 Hz increments. See Hertz.

Kerf
- A slice cut into the edge of an acoustical panel so that it can accept a spline (extrusion) to connect and mount an adjoining panel, providing a level surface at the joint or seam.

Isolation
- Resistance to the transmission of sound by materials and structures. The separation of airborne or mechanically transmitted energy.

Inverse square law - Any condition in which the magnitude of a physical quantity follows an inverse relationship to the square of the distance. In pure spherical divergence of sound from a point source in free space, the sound pressure level decreases 6 dB for each doubling of the distance.