Lateral Energy Factor
LEF is a parameter that, somewhat simplified, describes how much early sound arrives from the sidewalls to a listener’s position in relation to the sound that arrives late. This parameter is correlated to the subjective perception of spaciousness in a concert hall.

Lightweight partition walls
Internal walls usually formed from timber or metal studs with outer panels (gypsum, plywood) and a cavity filled with absorbing material (e.g. mineral wool) forming a acoustic double construction with high sound insulation properties. This can be compared to standard double marine panels.

Ln
Normalized sound pressure level for the impact noise in a room generated from a standardized tapping machine in another room.