sound waves in the room .
DIFFUSION AND ABSORPTION As well as manipulating room dimensions and / or angles , we must consider the importance of diffusion and absorption . Diffusing a waveform causes it to careen off its otherwise sonically destructive path . Absorption diminishes the waveform ’ s ability to reflect . It decreases the acoustic energy , potentially to the extent of completely eliminating reflection , especially in the upper-mid and high frequencies . The amount of absorption accomplished depends on the frequency of the waveform , the amplitude , and the absorption properties of the reflecting surface .
Whereas too many reflections and reverberations can cause problems for anyone trying to build a high-quality musical mix , a highly absorptive environment can also be problematic . Too much absorption robs the sound of life and sparkle . We ’ re typically much better off if the ambient sound is controlled through a combination of minimal absorption and well-designed diffusion .
Even a large room with an unnaturally short decay time feels lifeless and small . In an overly zealous attempt to provide controlled acoustics , the inexperienced acoustician might include too much absorption and not enough reflection . It takes a certain degree of reverberation to help the sound retain its personality and character . A complex diffuser breaks up the modes that occur when a large room has parallel surfaces , turning them into a more controlled-sounding reverberation .
MODE / STANDING WAVE / RESONANCE Modes , also called standing waves and resonances , are simply reflections that set up a pattern between surfaces in an acoustic space . The problems that modes create are destructive to the quality of the sound heard in the room . The term “ standing wave ” provides an accurate mental image of this acoustical problem . If a sound wave reflects back along the same path from which it came , it will reflect again once it problematic acoustical anomalies .
reaches its originating surface , then back again , and so on . In essence , the sound wave forms a pattern that , if visible to the naked eye , would seem to stand still in the room as it reflects back and forth . Such a standing wave poses multiple potential problems .
• If the sound wave follows the identical path on its reflection , increasing the size of the crest and trough of the affected frequency , a resonance ( an increase in energy from that frequency ) occurs .
• If the sound wave reflects out of phase in any degree with the original sound wave , some form of cancellation occurs .
• If the same modes occur between multiple opposing surfaces , they work together
Stage
Acoustic Design Principles in Action : The venue illustrated ( right ) was designed by the Walters-Storyk Design Group for Le Noirmont Catholic Church . It includes several excellent design principles that help control reflections . Notice the slightly non-parallel side walls and the convex angle protruding into the front and rear of the room . Any acoustic space with such an intelligent physical design is likely to exhibit few
Standing Wave
Standing Waves / Modes : This illustration demonstrates a complete waveform between two surfaces ; however , half of this waveform also fits between these surfaces ( one crest or one trough ). In addition , whole-number multiples of that crest or trough also fit evenly between those same surfaces , and likewise , create a standing pattern .