Subject: Ultrasonic natural sound recordings From: Eric Benjamin <ebenj@xxxxxxxx> Date: Wed, 18 Apr 2012 11:50:11 -0700 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>---455110525-924922231-1334775011=:52660 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Nicol Harper wrote:=0A> record frequencies up to at least 40kHz=0A> as inse= nsitive to sound-source direction as possible =0A> with a fairly flat frequ= ency response=0A=0AThat's an interesting project!=A0 With those requirement= s this effort is going to =0Abe an exercise in making compromises.=A0 You d= on't say what your requirements are =0Afor noise.=A0 That will be key in se= lecting the appropriate tradeoff between noise =0Aperformance and directivi= ty.=0A=0AIf you can allow that the microphone only needs to be omnidirectio= nal in the =0Ahorizontal plane you can orient the microphone pointing upwar= ds and then the =0Aresponse will be the same in every horizontal direction.= =A0 But if it is even 1/2" =0Ain diameter there will be significant roll-of= f due to the finite diaphragm =0Asize.=A0 Note that, if you know what the r= esponse of your microphone is it will be =0Arelatively easy to equalize it = to have flat axial response.=A0 But there's no way =0Ato equalize the diffe= rence between the axial response and the off-axis response.=0A=0AOne respon= se might be to use either a 1/4" or 1/8"=A0instrumentation microphone.=A0 = =0AFor reference, a 1/4" microphone has a diffuse-field response that is ab= out 6 dB =0Adown at 40 kHz relative to its axial response and an 1/8" micro= phone has a =0Adiffuse-field response that is about 3 dB down at 40 kHz rel= ative to its axial =0Aresponse.=A0 But these microphones are really too noi= sy for ordinary recording =0Aactivities.=A0 =0A=0A=0AI've used a Knowles FG= capsule for such recordings in the past, not the Avisoft =0Amicrophone but= the raw capsule that is used in it.=A0 The single sample that I =0Aused ha= d an axial response that was up about 5 dB at 12 kHz, back down to 0 dB =0A= at 20 kHz, and about -10 dB at 40 kHz.=A0 The self noise of the capsule was= 24 dB, =0AA weighted which is really quite good considering that the capsu= le is only 2.5 =0Amm in diameter.=A0 I didn't measure the polar patterns or= diffuse-field response =0Asince such a microphone is clearly good enough f= or ordinary audio bandwidth =0Arecordings.=A0 I would expect the performanc= e of the Avisoft product to be =0Asimilar.=0A=0AAnother alternative would b= e to use one of the Earthworks omni microphones.=A0 =0AThese are all 1/4" i= n diameter, and as such the 90 degree off-axis response is =0Aabout 3 dB do= wn at 20 kHz relative to on axis, so clearly not as good for your =0Apurpos= es as an 1/8" or 1/10" micrphone.=A0 But they are rugged and have good =0Ap= erformance.=0A=0AI hope this helps.=0A=0AEric Benjamin=0A=0A=0A____________= ____________________=0AFrom: Nicol Harper <nicol.harper@xxxxxxxx>=0ATo: AU= DITORY@xxxxxxxx=0ASent: Wed, April 18, 2012 9:09:51 AM=0ASubject: Ul= trasonic natural sound recordings=0A=0AHello.=A0I am new to this list. =0A= =0AI am making at set of natural sound recordings. I would like to be able = to =0Arecord frequencies up to at least 40kHz, with a microphone that is as= =0Ainsensitive to sound-source direction as possible and also preferably w= ith with =0Aa fairly flat frequency response. I will probably also want to = avoid sounds from =0Avibrations and knocks to the microphone during movemen= t of the microphone.=0A=0AI am currently using a zoom H2 recorder on mono m= ix with a 96kHz sampling rate, =0Aand carrying it carefully or using a trip= od.=0Ahttp://en.wikipedia.org/wiki/Zoom_H2_Handy_Recorder=0A=0A=0AI was thi= nking of maybe using a zoom H4 with a Knowle FGO microphone.=0Ahttp://www.a= visoft.com/usg/KnowlesFGO.htm=0Ahttp://en.wikipedia.org/wiki/Zoom_H4_Handy_= Recorder=0A=0ADoes anybody have any other suggestions, or know of anything = I should watch out =0Afor?=0A=0AI can spend up to a few thousand dollars.= =0A=0AAll the best,=0A=0ANicol Harper=0A ---455110525-924922231-1334775011=:52660 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable <html><head><style type=3D"text/css"><!-- DIV {margin:0px;} --></style></he= ad><body><div style=3D"font-family:arial, helvetica, sans-serif;font-size:1= 0pt"><DIV><FONT face=3DTahoma>Nicol Harper wrote:</FONT></DIV>=0A<DIV style= =3D"FONT-FAMILY: arial, helvetica, sans-serif; FONT-SIZE: 10pt">=0A<DIV sty= le=3D"FONT-FAMILY: times new roman, new york, times, serif; FONT-SIZE: 12pt= ">=0A<DIV style=3D"FONT-FAMILY: arial, helvetica, sans-serif; FONT-SIZE: 10= pt">=0A<DIV>> record frequencies up to at least 40kHz</DIV>=0A<DIV>> = as insensitive to sound-source direction as possible </DIV>=0A<DIV>> wit= h a fairly flat frequency response</DIV>=0A<DIV> </DIV>=0A<DIV>That's = an interesting project! With those requirements this effort is going = to be an exercise in making compromises. You don't say what your requ= irements are for noise. That will be key in selecting the appropriate= tradeoff between noise performance and directivity.</DIV>=0A<DIV> </D= IV>=0A<DIV>If you can allow that the microphone only needs to be omnidirect= ional in the horizontal plane you can orient the microphone pointing upward= s and then the response will be the same in every horizontal direction.&nbs= p; But if it is even 1/2" in diameter there will be significant roll-off du= e to the finite diaphragm size. Note that, if you know what the respo= nse of your microphone is it will be relatively easy to equalize it to have= flat axial response. But there's no way to equalize the difference b= etween the axial response and the off-axis response.</DIV>=0A<DIV> </D= IV>=0A<DIV>One response might be to use either a 1/4" or 1/8" instrume= ntation microphone. For reference, a 1/4" microphone has a diffuse-fi= eld response that is about 6 dB down at 40 kHz relative to its axial respon= se and an 1/8" microphone has a diffuse-field response that is about 3 dB d= own at 40 kHz relative to its axial response. But these microphones a= re really too noisy for ordinary recording activities. </DIV>=0A<DIV>= </DIV>=0A<DIV>I've used a Knowles FG capsule for such recordings in t= he past, not the Avisoft microphone but the raw capsule that is used in it.= The single sample that I used had an axial response that was up abou= t 5 dB at 12 kHz, back down to 0 dB at 20 kHz, and about -10 dB at 40 kHz.&= nbsp; The self noise of the capsule was 24 dB, A weighted which is really q= uite good considering that the capsule is only 2.5 mm in diameter. I = didn't measure the polar patterns or diffuse-field response since such a mi= crophone is clearly good enough for ordinary audio bandwidth recordings.&nb= sp; I would expect the performance of the Avisoft product to be similar.</D= IV>=0A<DIV> </DIV>=0A<DIV>Another alternative would be to use one of t= he Earthworks omni microphones. These are all 1/4" in diameter, and a= s such the 90 degree off-axis response is about 3 dB down at 20 kHz relativ= e to on axis, so clearly not as good for your purposes as an 1/8" or 1/10" = micrphone. But they are rugged and have good performance.</DIV>=0A<DI= V> </DIV>=0A<DIV>I hope this helps.</DIV>=0A<DIV> </DIV>=0A<DIV>E= ric Benjamin<BR></DIV>=0A<DIV style=3D"FONT-FAMILY: arial, helvetica, sans-= serif; FONT-SIZE: 10pt">=0A<DIV style=3D"FONT-FAMILY: times new roman, new = york, times, serif; FONT-SIZE: 12pt"><FONT size=3D2 face=3DTahoma>=0A<HR SI= ZE=3D1>=0A<B><SPAN style=3D"FONT-WEIGHT: bold">From:</SPAN></B> Nicol Harpe= r <nicol.harper@xxxxxxxx><BR><B><SPAN style=3D"FONT-WEIGHT: bold">To= :</SPAN></B> AUDITORY@xxxxxxxx<BR><B><SPAN style=3D"FONT-WEIGHT: bol= d">Sent:</SPAN></B> Wed, April 18, 2012 9:09:51 AM<BR><B><SPAN style=3D"FON= T-WEIGHT: bold">Subject:</SPAN></B> Ultrasonic natural sound recordings<BR>= </FONT><BR>Hello. I am new to this list. =0A<DIV><BR></DIV>=0A<DIV>I a= m making at set of natural sound recordings. I would like to be able to rec= ord frequencies up to at least 40kHz, with a microphone that is as insensit= ive to sound-source direction as possible and also preferably with with a f= airly flat frequency response. I will probably also want to avoid sounds fr= om vibrations and knocks to the microphone during movement of the microphon= e.</DIV>=0A<DIV><BR></DIV>=0A<DIV>I am currently using a zoom H2 recorder o= n mono mix with a 96kHz sampling rate, and carrying it carefully or using a= tripod.</DIV>=0A<DIV><A href=3D"http://en.wikipedia.org/wiki/Zoom_H2_Handy= _Recorder" rel=3Dnofollow target=3D_blank>http://en.wikipedia.org/wiki/Zoom= _H2_Handy_Recorder</A><BR><BR></DIV>=0A<DIV>I was thinking of maybe using a= zoom H4 with a Knowle FGO microphone.<BR><A href=3D"http://www.avisoft.com= /usg/KnowlesFGO.htm" rel=3Dnofollow target=3D_blank>http://www.avisoft.com/= usg/KnowlesFGO.htm</A><BR><A href=3D"http://en.wikipedia.org/wiki/Zoom_H4_H= andy_Recorder" rel=3Dnofollow target=3D_blank>http://en.wikipedia.org/wiki/= Zoom_H4_Handy_Recorder</A><BR><BR>Does anybody have any other suggestions, = or know of anything I should watch out for?<BR><BR>I can spend up to a few = thousand dollars.<BR><BR>All the best,<BR><BR>Nicol Harper<BR></DIV></DIV><= /DIV></DIV></DIV></DIV></div></body></html> ---455110525-924922231-1334775011=:52660--