In somewhat oversimplified terms, the analysis and subsequent design additions for improving the acoustics of this type of room would include (not necessarily in this order):

1. Low-Frequency Modal Analysis
The first step is an analysis of the room's geometry for low-frequency standing-wave relationship. In very simple terms this is the tendency of a room to resonate naturally at certain frequencies (usually base tones up to about 300hz). A well-balanced room will have these tendencies at as even a frequency distribution as possible. The ratios of the three primary axes of the room determine this tendency. If we have the luxury of creating these ratios prior to analysis, this makes things considerably easier. But in the case of the McCue living room, this shape was already determined, thus we were only able to analyze the room profile and determine if low-frequency absorption would be required to correct standing-wave anomalies.

Luckily this was not really the case in this room. The room ratios are quite acceptable (I'll spare everyone the math on this problem!). Additionally, since the McCues did not consider it critical to have acoustic isolation in the living room, the walls and ceiling for the room were not constructed in an especially stiff fashion. This lets the walls and ceiling to act as a type of absorber for these tones, allowing a certain amount of low-frequency energy to simply leave the room. (In a more isolated situation, such as a dedicated basement home theater, balanced low-frequency response would become a bigger issue to deal with.)

2. Mid- to High-Frequency Reflection Control
This is probably the most important area of concern for the McCues. Ensuring a reverberant room — in other words, making sound remain in the room as long as possible — is the type of acoustic control that will benefit their living room the most. However, harsh reflections, such as the bouncing of sound between the two parallel hard surfaces of the ceiling and floor, is not desirable. The room design called for a hardwood floor and a parallel gypsum ceiling. Additionally, the center of the room has a vaulted, concave-curved gypsum surface around its perimeter. My initial suggestion was for these surfaces to be detailed with sound-absorption material covered with fabric, but that was rejected for esthetic reasons. The solution we all settled on calls for the use of a relatively new product that is, in essence, absorptive plaster. It is applied in a three-step process, resulting in a surface that appears just like plaster (or gypsum board), but has the absorptive qualities of most types of insulation. Harsh reflections (and subsequent tonal imbalances) are thus "erased" from the center of the room, while still maintaining the look and feel of the original design.

3. David's Piano Area
David created what essentially is a small stage within the room, an area in which our most important concern was what David himself will hear when he plays piano. The area in the room is slightly raised, but has a lowered ceiling. As mentioned above, most of the room has a high, central vaulted area giving the room increased volume and more breathing room for sound to naturally propagate. But original designs called for the lowered ceiling of this space to be continuous with the return soffit in the room and thus constructed out of gypsum board or plaster. Bearing in mind the choice of wood for the room's flooring, this again would result in harsh echoes — called flutter echoes — in this area, also causing frequency misdistribution.

The solution was to cover this portion of the lowered ceiling in the piano alcove with fabric — which is acoustically transparent —and then install diffusive panels above the fabric in the ceiling volume. For this we used a pre-fabricated diffusion element (2 feet by 2 feet by 8 inches deep), which has good mid- and high-frequency diffusion characteristics. This will keep all of the piano "energy" in the room while helping to scatter it more evenly throughout, reducing harsh reflections and tone distortions — creating a more accurate and even distribution of frequencies where David is seated, our ultimate goal.

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