There are three types of standing waves . Axial standing waves reflect between two surfaces . Tangential standing waves reflect around the room , touching four walls . Oblique standing waves touch all six of the primary room surfaces ( side walls , front and rear , and ceiling and floor ).
to increase the overall anomaly within the space .
Any room in which the same frequency stands between multiple surfaces ( side walls , front and back walls , and ceiling and floor ) will typically need acoustical treatment to enable reliable performances , mixes , and recordings . absorption or diffusion . Take note of opposing hard , flat surfaces . Something needs to break up the natural reflection back and forth between parallel walls in order to eliminate flutter echoes .
CONCAVE ANGLES A concave angle , such as a typical corner in a room , focuses reflections in a particular direction . Because most of the flat surfaces in any acoustical environment form concave angles at the corners , there ’ s no way we can avoid concave angles . However , we must realize the effect they have on room acoustics and adjust our setup accordingly .
For deeper dive into calculating the frequencies of standing waves , refer to The Ultimate Live Sound Operator ’ s Handbook .
FLUTTER ECHO Flutter echoes can be heard after the sound source ceases . They can sound like a ringing or hissing sound . Depending on the distance between the opposing surfaces , flutter echoes can also sound like a series of fast distinct repeating delays that can last for a half second or more . As mid frequencies stand , especially between sidewalls , they resonate after the source sound diminishes . Try clapping your hands in an empty room with a lot of hard surfaces . The ringing after you clap is probably flutter echo . The flutter is a repeating echo back and forth between opposing surfaces , so in smaller rooms it ’ s faster , and in larger rooms it ’ s slower . Rooms with reflections larger than about 50 ms exhibit flutter echoes that sound like distinct delays fading away over time .
Flutter echoes are easily controlled using
Concave angles focus sound waves at a specific point . In the recording studio , contrary to the effect of the concave angle , we traditionally make an effort to randomize and confuse audio sound wave focus for our acoustic purposes . Whereas we must avoid focusing and providing the opportunity for sonic patterns to accumulate , the large concave design is the basis of the amphitheater . In a concert setting , musicians positioned in the “ bowl ” enjoy the fact that their performance is focused on the audience .