Definition of Diffuse Sound Field (Phil McCandless )


Subject: Definition of Diffuse Sound Field
From:    Phil McCandless  <pmccand@xxxxxxxx>
Date:    Fri, 25 Jan 2013 21:35:35 -0800
List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>

--1228296801-519873433-1359178535=:18267 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Thanks to all those who helped answer my questions about the diffuse sound = field.=A0 Unfortunately, I no longer work in a university setting, and ther= e is no acoustics laboratory near by, so I had to improvise...and I have to= say, I came up with the PERFECT solution for a diffuse field reverberant e= nclosure... I stopped by a local shipping container rental contractor a few miles up th= e road and found two dozen 10x12x40 heavy-duty contractors shipping contain= ers.=A0 The one I chose had 1/8" thick corrugated metal sides (which I thin= k would not be good for high frequency propagation), but I ran an extension= cord out to the box, unloaded the manikin, amplifier, speaker and computer= and started testing the microphone response 360 degrees in 30 degree incre= ments in the horizontal plane. The analysis of the frequency response show graphs overlaped almost perfect= ly on top of one another at all horizontal angles of manikin rotation.=A0 I= found less than +/-1dB variation (response smoothed with 1/3 octave res) b= etween 30 Hz and 12 KHz.=A0=A0 RT 60 is still being looked at, but it is ve= ry long at a wide range of frequencies.=A0 I am also calculating DI, but I = assume that the container makes a very effective acoustic reverberation cha= mber. I am reporting my results for the benefit of someone else that may need acc= ess to a simple, inexpensive, yet effective reverberant chamber. Phil Mc C.an.dless --1228296801-519873433-1359178535=:18267 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable <table cellspacing=3D"0" cellpadding=3D"0" border=3D"0" ><tr><td valign=3D"= top" style=3D"font: inherit;">Thanks to all those who helped answer my ques= tions about the diffuse sound field.&nbsp; Unfortunately, I no longer work = in a university setting, and there is no acoustics laboratory near by, so I= had to improvise...and I have to say, I came up with the PERFECT solution = for a diffuse field reverberant enclosure...<br><br>I stopped by a local sh= ipping container rental contractor a few miles up the road and found two do= zen 10x12x40 heavy-duty contractors shipping containers.&nbsp; The one I ch= ose had 1/8" thick corrugated metal sides (which I think would not be good = for high frequency propagation), but I ran an extension cord out to the box= , unloaded the manikin, amplifier, speaker and computer and started testing= the microphone response 360 degrees in 30 degree increments in the horizon= tal plane.<br><br>The analysis of the frequency response show graphs overla= ped almost perfectly on top of one another at all horizontal angles of manikin= rotation.&nbsp; I found less than +/-1dB variation (response smoothed with= 1/3 octave res) between 30 Hz and 12 KHz.&nbsp;&nbsp; RT 60 is still being= looked at, but it is very long at a wide range of frequencies.&nbsp; I am = also calculating DI, but I assume that the container makes a very effective= acoustic reverberation chamber.<br><br>I am reporting my results for the b= enefit of someone else that may need access to a simple, inexpensive, yet e= ffective reverberant chamber.<br><br>Phil Mc C.an.dless<br></td></tr></tabl= e> --1228296801-519873433-1359178535=:18267--


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