These types of waves act like resonators for a room, creating 0 crossing zones.
<aside> 📈 Definiton
Waves of a frequency which has the exact parameters of of the room. These waves fade out a lot slower in comparison to the other frequencies (longer reverb).
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It is best to avoid parallel walls when building studios or rooms. Therefore, a cube would be the worst room possible.
Also, try not to have multiple of dimension in a room (L = hx2 or L= lx2)
Concave walls
Sound is really bad, the wall acts like a satellite dish.
Convex walls
Sound is much better, diffuses the sound.
It is better to have a room which has even cancelation throughout the room:
The pressure maximum is near the walls.
Pressure maximum