The absorbed sound energy is not equal across all frequencies, however, usually causing a shift in tonal perception, with higher frequencies the most easily absorbed. 2), as opposed to reflecting sound energy. Too much intact reflected sound energy causes sound in rooms to become unwanted, uncomfortable, and unavoidable noise.įigure 1 – Original sound: red lines reflected sound: blue and green linesīecause absorption is the one process many people think of when referring to acoustical treatments, let’s look at an easy definition of sound (acoustic) absorption before looking at diffusion: acoustic absorption is the process of reducing sound energy (see Fig. Accurately hearing original sound, whether from voices, musical instruments, or loudspeakers, becomes difficult. Equally problematic, delays from sound reflections cause timing (or “phase”) errors – these disrupt sound-stage imaging and cause frequency additions and subtractions called “comb-filtering” (from the shape of the resulting frequency-response peaks and dips). Multiple delays from many flat surfaces, combined with original sound, add too much echo and reverberation. Because the reflections are traveling farther, they are delayed compared to the original sound (see Fig. These strong, intact reflections cause problems when they’re-combine with the original sound, which arrives at our ears directly through air without reflecting. Why would we need better sound in rooms? Because most walls, floors, and ceilings are made up of hard, flat surfaces which strongly reflect sound energy intact. Absorption and diffusion are called room treatments and are used for “better sound”. Keep in mind that absorption and diffusion are NOT the same as the methods used to reduce sound leakage into and out of a room, usually called “soundproofing,” which results in “less noise” (noise defined as any unwanted sound). In large acoustically-designed spaces, like concert halls, diffusion is most often built into the room’s physical geometry – the shapes of walls and ceilings (floors are nearly always flat and act as large flat-surface reflectors, even if sloped). Both tools will improve sound perception in spaces that, if left untreated, would be a bad influence on sound. That’s right – there are only two acoustical tools available to improve sound inside a room, whether that room is huge or tiny: sound absorption and sound diffusion. This seems a bit odd, because it’s one of only two tools in our “Better Sounding Room” toolbox. However, in the wide, wide world of acoustics, the sound diffusion process and tools are widely misunderstood, even by some acoustics professionals. Here’s an easy definition: diffusion is the method of spreading out sound energy with a diffusor (diffuser) for better sound in a space. Posted by AcousticalSurfaces on 11:21 pm | Leave a Comment
What is Sound Diffusion (and Absorption)?
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