Apr 8, 2010 12:00 PM, By Bob McCarthy
Purchasing and installing absorption and diffusion devices are middle steps in the big picture of tuning the room. Before these steps, we must ascertain the needs, and after them, quantify their effect. For installations of an existing space, an acoustic analyzer will be key to the before and after. The analyzer must be capable of seeing the details of diffuse reflection patterns, reverberation decay timing, and the strength of the direct sound, among many other things. Let’s look at some of the spectral analysis tools used to evaluate the room and finally to tune the loudspeakers in the room.
EASERA (Electronic and Acoustic System Evaluation and Response Analysis), a product of Renkus-Heinz, brings into a laptop PC with a soundcard, a suite of acoustical analysis tools that a few years ago would have filled several equipment racks. Complex analysis of room acoustic functions can be gathered via a variety of stimulus signals including time-delay spectrometry, a sweep, a maximum-length sequence, or a noise-excitation signal. The data can then be used immediately or post-processed off site into a huge variety of computations too large for this article.
For live sound applications, the sister program SysTune provides dual-channel analysis of the system with all of the data relevant to equalization and sound system optimization, including the capability to continue the tuning with music as the source signal.
Measuring Room Acoustics
The 7841 DIRAC system, distributed by Brüel & Kjær, is an acoustics measurement software tool developed by Acoustics Engineering. DIRAC room acoustics software type 7841 uses impulse responses for measuring a wide range of room acoustical parameters including reverberation time, early decay rate, clarity, intelligibility, and much more.
Other options of excitation signal include the internally generated maximum-length sequence (MLS) or sweep signals through a loudspeaker sound source. Survey measurements are easily carried out using a small impulsive sound source, such as a blank pistol or even a balloon.
Meyer Sound’s SIM 3 is a comprehensive multichannel sound system/room analysis system designed for realtime optimization of installed loudspeaker systems. The system interfaces directly into the loudspeaker system’s signal processing to provide detailed info to find the best delay, level, and equalization settings for optimum response in the room. The system has configurations appropriate for all sizes from studios to stadiums.
Rational Acoustics is taking orders for v.7, the next generation of Smaart. The new version features enhanced stability, higher resolution, and multichannel capability far beyond the previous versions. Smaart has room acoustic analysis capabilities as well as the realtime features required for live sound tunings.
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