Shown in the photograph is a partial panorama of the listening room with a baffle in place for measurement.
This position (and that of the
microphone) was found after more than 90 minutes of pushing around the
baffle and the microphone while continuously taking impulse measurements
to evaluate the severity of room reflections.
Sonic reflections in the data are unwanted, but mostly unavoidable in small room situations.
If 'clean' data without reflections is the goal, then the sonic reflections must be avoided or limited. One common method used, is to truncate the length of the data sample to the duration that does not contain any reflections. The sample sizes in the Listening Room data are about 7.03mS in length, equivalent to 432 data points, which implies a low frequency limit of approximatley 135Hz for semi-anechoic (on a ground plane) measurement.
In the 'Measurements Issues' section at the ALSR Table of Contents is detailed some of the problems involved in Maximum Length Sequence (MLS) measurement as analyzed by the Fast Fourier Transform.
At left is a look down the microphone toward the baffle. Note the taped 'position references' on the floor beneath the baffle. There was a similar reference for the microphone position.
During the time of the three weekends necessary for the completion of
this portion of the RD75 Dipole Baffle Study the listening room stayed
'disassembled' - no changes whatsoever were made
to the setup! 'BIG' science at home, requires control and discipline, and
tolerant spouses or pardners.
The Listening Room Measurements - Table of Contents.
The Listening Room Measurements -
Two-Sided Baffles - Table of Contents.
The RD75 Dipole Baffle Study - Table of Contents.
Acoustic Line Source Research - Table of Contents.
