Reflective
 Surfaces in which certain frequencies bounce off easily
 Absorptive
 Surfaces that absorb certain frequencies and “deaden” the sound.
 Diffusive
 A mix of absorption and reflection. Essentially, diffusors are meant to “scatter” sound. Diffusers may be natural or man made. They may be random or they may follow a mathematical formula.
 Convex
 Outwardly rounded. Many diffusers are some type of convex and rarely concave.
 Examples of natural diffusers
 petrified wood, tree bark, stone walls, exposed brick, broken brick
 Primitive Root Sequence or the Quadratic Residue Formula.
 Diffraction Grating
 General term for a directional diffusers, usually called an RPG if it follows math.
 RPG
 Reflection phase grating- minute parallel lines (usually hardwood/plastic filler) that is meant for directional diffusion
 Skyline
 Resembles a city skyline. These diffusers follow the QRD formula as well, but are designed to be a “3D” diffuser, providing omnidirectional scattering.
 Inverse Skyline
 Same concept as a regular skyline, but the inverse mold of a typical design
 Convex Panels
 These types of diffusers are sometime semi-resonators. They trap a certain bandwidth of frequency inside, and scatter higher frequency.
 Axial Modes
 Based on the room’s three main axes: length, width, and height Between these walls, standing waves (resonance) travel along each axial mode, creating a range of frequencies that are accentuated according to the layout of the room. This is why certain frequencies are heard better in certain parts of the room.
 Standing waves
 A wave of sound that bounces between two or more surfaces emphasizing one frequency over others. The area between two parallel walls resonate at certain frequencies; a standing wave IS resonance created by two PARALLEL walls.
 First Live Face
 First interference of the primary axial mode. It’s good to place an absorber in front of wall to avoid heavy reflection and phasing.
 Examples of Absorbers
 Bass traps, Korner Killer (made by aurelex), Baffles, Banners, Clouds
 Bass Traps
 Made to generally take in excess bass in a room. They can’t be bandwidth oriented in design. THey can only be deep enough to accomodate low frequencies.
 Korner Killer
 Made by Aurelex. Specifically meant for installation in corners. May be installed vertically or horizontally.
 Two kinds of baffles
 go-bos (go-betweens) and hanging
 Go-Bos
 Go-betweens. Mobile baffles, usually reflective/diffusive on one side, absorptive on the other.
 Baffles are meant to obstruct reflections between __________ walls
 parallel
 kinds of hanging absorbers
 hanging baffles, hanging banners and Clouds
 Clouds
 Used to be called “Contra Carpet”. flat absorbers that hang parallel to the ceiling. Sometimes they are meant to resonate specific frequencies and may be partially
 Splaying
 rebuilding the wall or walls so that they are not parallel with one another. Usually said as “the wall is splayed x degrees”or “the wall is canted x degree”. 6 degrees usually the maximum, normally referenced from a window.
 Sound Lock
 2 doors installed in series. This is the best method of maintaining the consistency of the wall (or double wall) without using a single, extremely heavy door. The inside of the sound lock should be heavily absorptive
 Resonance
 The frequencies that an object vibrates at.