Quote:
Originally Posted by PaulP  (I wrote)
Testing the room would be helpful. From the height of your ceiling you
should have a nice null around 150 hz in the middle vertically, probably
quite near your head when seated. |
I'm near the end of my second read of Master Handbook of Acoustics and
came across some info this morning showing the above to be in error.
At the mode frequency (speed of sound/twice the length) there will be a
null in the center of the room (a plane perpendicular to the direction of
measurement). For a height of 7'5" the mode is 76 hz and at that frequency
there will be a null everywhere in the room at a height of 3'8". But there
will also be a peak at twice that frequency 152 hz followed by a another
null at 228 hz, another peak at 304 hz and so on at multiples of 76Hz.
See the following excerpt from the book :
Two wall resonance
(click on the blue arrow to expand the box, then scroll up bit)
At the walls, or in the above case at the floor and ceiling, the mode and
all its multiples are peaks, which is why that's a good place to put absorption.
Corners have two walls coming together so they're even better spots as
you can affect two modes at the same time.
Paul P