MOTM

I used a similar method for determining the proper frequency for 
bass traps in my control room.  I recorded a series of sine waves 
into ProTools at different frequencies then truncated them at the 
zero crossing points.  I played them through a set of monitors (a 
pair of JBLs that I had the manufacturers frequency response plot 
for.)  I recorded the tone bursts back into ProTools using a flat 
mic and preamp.  The microphone was placed at the console center 
listening position.  I tried several different locations for the 
monitors to eliminate standing waves but mostly used the near field 
position.  I then determined the room response by adjusting the 
amplitude of the re-recorded tone bursts for the frequency response 
of the monitors.  I also looked at the amount of time the 
room "rang" at the different frequencies although some of this was 
probably due to the speaker cones ringing.
I did determine an optimum frequency for bass traps and constructed 
them to attenuate that frequency.  That and the overall shape of the 
room as well as the combination of absorbant and reflective 
materials yielded a room within 3 db of flat and with great imaging.
The downside was that in an attempt to "excite" the room into 
resonance I blew the woofers in both monitors.  So be careful!!!
I was not in the room when I tested it.  I value my hearing!
Another interesting technique is to place a white syrofoam ball 
where your head will be (in the center monitoring position) cover 
all reflective surfaces with aluminum (aluminium for you Brits) foil 
shiny side up.  Take a laser pointer and hold it where your monitors 
will be and see whether you can prevent any reflections from hitting 
the styrofoam by adjusting the angle of your console and other 
equipment.  You'd be amazed at how much the elimination of first 
order reflections will improve the sound of a room.

One other point relating to what Roger just posted.
If you monitor at a level of 80-85 db you will find that your 
perception of loudness as well as pitch is improved.  You will also 
be protecting your hearing and be able to listen attentively for a 
much longer period of time without as much ear fatigue.  
There have been recent studies that show as much.  
And those of us over 50 need whatever edge we can get.
I almost always rely on nearfield monitors as well, but I also use a 
Subwoofer.  I try to keep it flat with the nearfields, but it's 
difficult to do at different volume levels due to the loudness 
factor.  I have found that if I have that perception of "felt" bass 
at a lower volume level I don't feel so inclined to crank up the 
volume, although every once in a while the old rocker in me comes 
out and the volume goes up.