 times 270 hits equals 5,238 feet or nearly a mile! This takes 5,238/1,130 equals 4.6 seconds to do.
What denotes good acoustics in a small room?As in any room, the goals for the acoustics of a small room depend on what the room's function is to be. If the room is to be used for listening to recordings, then the acoustics of the room are made to be subordinate to those on the recordings and reproduced by the sound system. If the room is for lectures, then the acoustics of the room are made to be comfortable with an optimum signal-to-noise ratio for the listeners.
The acoustics of individual music practice rooms are adjusted to mimic the acoustics of the large performance halls where the polished performance will be made. Studios are designed to add pleasant and adjustable room acoustics to sound recordings. Control rooms are made to optimize their stereo monitoring function. Teleconference rooms are built to optimize the acoustic presence of conference participants.
For small rooms, these acoustic goals are met by controlling the timing, strength and location of sound waves within the room. This requires the exact placement of various types of acoustic treatment. The type of treatment to be used depends on the region of soundwaves to be controlled.
Controlling soundwaves in small roomsLow-frequency soundwaves in the "pressure region" can be controlled using active noise control (see "Silence, Please," Sound Advice, Walls & Ceilings, September 2000). This technique uses a microphone to pick up the low frequency soundwave. It then uses a loudspeaker in the room to create a mating soundwave having the same amplitude but opposite phase (i.e., the mating soundwave pressure goes down when the original soundwave pressure goes up and vice versa). The result is that the two soundwaves tend to cancel each other out.
Low- to mid-frequency soundwaves in the "normal mode region" can be controlled using diaphragm and helmholtz-type sound absorbers (see "Helmholtz Resonator Sound Absorbers," Sound Advice, W&C, April 2000). In the diaphragm absorber, a wall surface is made to vibrate like a drumhead at the desired frequency. Soundwaves at this frequency tend to pass right through the wall with little resistance. Once the sound energy is outside the wall, it is kept out by absorbing it with massive layers of sound-absorbing material. Helmholtz absorbers trap soundwaves in tuned cavities. These can be recognized by their perforated or slotted faces.
Mid- to high-frequency soundwaves in the "diffusion region" can be dispersed with the use of diffusers. The most common diffusers are shaped like pyramids and attach to walls and ceilings. These diffuse soundwaves by scattering them in four different directions. Other diffusers look like flat sound panels, but are really an array of reflectors and absorbers, arranged in a mathematical pattern, which scatters soundwaves in many directions.
High-frequency soundwaves in the "specular reflection region" can be handled with sound absorbing panels and sound reflectors. Since, in small rooms, soundwaves only last a short time, it is critically important to place diffusers, absorbers and reflectors only where they are sure to intercept the soundwave that you want to control.
Classroom acoustics in the United States are so poor that students are not able to hear 70 percent of what their teachers say. One third of office workers say they are very disturbed by noise with a resulting loss in productivity.
It's interesting to read the complaints of Vitruvius, an architect from the first century B.C., that "improvements in architecture and the arts are always held back by baseless approval of inferior methods under the influence of social connections."