Flutter Echo - Avalon Idea User Manual

8.2 Flutter Echo

These parallel, reflective surfaces can also produce a different audible
problem. If there is little absorption at higher frequencies, a musical transient
containing high frequencies, such as a hand clap or the strike of a percussion
instrument, can be heard bouncing repeatedly between the surfaces. Called
flutter echo (or slap echo), these multiple reflections can obscure musical
detail. The situation is analogous to standing between two parallel mirrors,
when the outline of your reflection becomes more difficult to discern, due to
the additional reflected images present.
Again, it is only necessary to reduce the reflectiveness of one of the surfaces
in each pair of surfaces to eliminate flutter echo. Since we are concerned
with the high frequencies, any soft material is appropriate. Drapery or fabric
wall hangings are quite effective on the walls. Bookshelves also work well by
breaking up the flat surfaces. Carpeting should eliminate potential problems
between the floor and ceiling.
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