Subject: Re: [AUDITORY] AUDITORY Digest - 7 Jun 2013 (#2013-135) From: Tom Campbell <tom_campbell75@xxxxxxxx> Date: Sat, 8 Jun 2013 06:10:12 +0000 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>--_b8227f93-b6bf-478d-a8c3-a2c1a988ed8d_ Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hi Massimo=2C =20 I worked with an ETS Lindgren room at UC Davis with serious shielding. It b= locked mobile phone signals even in the control room about 4 m from the cag= e. This is overkill as the brain signals of interest are of a much lower fr= equency. There were some high frequency oscillation in the EEG with a funda= mental around 1.6 kHz=2C which whilst not an issue for auditory long latenc= y responses=2C became more problematic when recording at higher sampling ra= tes=2C e.g. for ABR=2C as visible in: =20 =0A= =0A= Campbell=2C T.A.=2C Kerlin=2C J.K.=2C Bishop C.W.=2C &=0A= Miller=2C L.M. (2012). Methods to eliminate stimulus transduction artifact = from=0A= insert earphones during electroencephalography. Ear & Hearing=2C 33=2C 44-5= 0. doi: 10.1097/AUD.0b013e3182280353 =0A= =0A= We also recorded "EEG" from a bucket of salt water and still found the osci= llations were still there.=20 =20 So we stripped the lab of equipment and went in with an oscilloscope and an= tenna. Whether using a power source for the oscilloscope inside or outside = the cage=2C there it was=2C the high frequency oscillation. We contacted fa= cilities to verify if there was a common ground in the control room=2C insi= de the cage and for the cage. Apparently there had been a recent change an= d the cage had been given a separate ground. Something to do with the build= ing being struck by lightning and protecting equipment and people touching = that equipment=2C such as an EEG participant. The head of the lab=2C a phys= icist=2C used the expression of "chasing a phantom"=2C at which point I vis= ualised the omnipresent source of the high frequency oscillation haunting m= e day and night=2C and laughing at me. So the rooms can have problems and t= he extent of the problem can vary with what you do in the lab. We did not= =2C however compare responses inside and outside the shielded room=2C as is= a very interesting question. =20 Shielding needs to be grounded for the cage to be effective. Also=2C it is = worth emphasising=2C the ideal is that you have a common ground for all ele= ctrical equipment near or in the lab and this is the ground of the cage=2C = assuming you never have a participant connected to electrical equipment wit= h that ground in a thunderstorm. You may be able to improve the effectivene= ss of the cage by the removal of a green copper oxide that can appear on th= e fingers of the door of an ETS lindgren shielded room. This can be done by= regular cleaning off with rubbing alcohol or with a severe build up sandin= g with emory paper. This might reduce the hysteresis problem of the charge = carriers getting trapped that one of the other responses mentioned=2C as wi= ll be particularly severe if the cage is not properly grounded. There is a tendency now to do more EEG research outside of the shielded roo= m with many different kinds of EEG system. I have heard a distributor of a = high cost systems with active electrodes suggest that there were no appreci= able signal:noise gain to be found with a shielded room and such a system. = However=2C I know of no systematic independent study that compares auditory= evoked potential signal:noise with such a system inside or outside well-ma= intained shielding with a common ground with electrical equipment. It would= be of practical and financial significance to compare the signal-to-noise = of evoked potentials recorded with different EEG systems with passive and a= ctive electrodes under these different conditions of no shielding versus we= ll-maintained shielding with a common ground. I'd be very interested what y= ou hear of people's experiences. Best regards=2CTom. =20 > Date: Sat=2C 8 Jun 2013 00:01:11 -0400 > From: LISTSERV@xxxxxxxx > Subject: AUDITORY Digest - 7 Jun 2013 (#2013-135) > To: AUDITORY@xxxxxxxx >=20 > There are 2 messages totalling 153 lines in this issue. >=20 > Topics of the day: >=20 > 1. Sound proof booth and EEG recording [the revenge] (2) >=20 > ---------------------------------------------------------------------- >=20 > Date: Fri=2C 7 Jun 2013 09:24:56 +0200 > From: Massimo Grassi <massimo.grassi@xxxxxxxx> > Subject: Sound proof booth and EEG recording [the revenge] >=20 > Dear list member=2C >=20 > the question I submitted the other day raised an unexpected response:=20 > many of the people I came in contact with were actually *unhappy* of the= =20 > electrical shielding of the booth. >=20 > I quote here the words of Dave Hairston: "While having a fantastic=20 > Faraday cage is theoretically great=2C in reality in can cause as many=20 > problems as it solves. For instance we have discovered that in many=20 > cases if you have ANY electrical devices inside=2C such as monitors=2C=20 > keyboards=2C whatever=2C it traps and bounces the power line noise much=20 > worse than just doing in a normal office room." >=20 > Here=2C we are definitely going to take some electrical device inside the= =20 > booth. Because the electrical shielding has a cost (about 5000 euros)=20 > I'm now wandering whether it is worth to spend this money. >=20 > Here comes the question (addressed to those like me that must take some=20 > electrical devices inside the booth): did the electrical shielding of=20 > your booth improve substantially the quality of your recordings? >=20 > Thank you all in advance=2C > m >=20 > --=20 > http://www.psy.unipd.it/~grassi/ > http://www.springer.com/978-1-4614-2196-2 > http://www.finveneto.it/nuoto_schedaatleta.php?id_atleta=3D73076 >=20 > ------------------------------ >=20 > Date: Fri=2C 7 Jun 2013 11:16:55 +0200 > From: Alain de Cheveigne' <alain.de.cheveigne@xxxxxxxx> > Subject: Re: Sound proof booth and EEG recording [the revenge] >=20 > A few comments on suggestions so far. >=20 > (1) Patch-panel vs holes. A patch panel is tidy=2C a hole is =3D > future-proof. I'd go for the hole=2C as a sound booth is a long-term =3D > investment. It shouldn't have too much impact on acoustic isolation=2C i= f =3D > properly designed.=3D20 >=20 > (2) The hole. Make it large enough to pass the largest expected =3D > connector (e.g. a UK plug). For a double-walled booth there is little = =3D > benefit in offsetting the holes in the inner and outer shells=2C because = =3D > this makes little difference at low frequencies. It is important to =3D > make the holes air-tight after passing the cables. A sand-box on each = =3D > side sounds like an effective solution=2C but probably a bit of a hassle = =3D > when passing cables. IAC suggests filling the space around the cables = =3D > in the hole with "pugging" (compressible foam or clay). For a set of = =3D > booths that we're ordering=2C I asked them to equip each hole with a box = =3D > with screw-on cover to allow the cables to be laid flat for a more =3D > effective pugging. Someone suggested more than one hole to separate AC = =3D > cables from the rest : good idea. >=20 > (3) AC power in the booth. If possible=2C ban it. Use filtered DC for = =3D > the lights. Don't install AC outlets in the booth (if you need AC at a = =3D > later time=2C you can pass an extension via the hole).=3D20 >=20 > (4) Equipment. If possible=2C ban AC-powered stuff from inside the booth= =2C =3D > as well as things such as displays that can produce lots of =3D > electromagnetic interference components. Equip your booth with a window = =3D > such that you can place a monitor outside visible to the subject. >=20 > (5) Shielding. There are several things to consider. Major sources of = =3D > EM (electromagnetic) interference are AC power lines=2C electronic =3D > equipment (computers=2C displays=2C switching power supplies)=2C and radi= o =3D > waves (e.g. cell phones and cell phone relays). The EM field includes = =3D > both an electric and a magnetic component. For low frequencies (power = =3D > lines) the E and M are independent=2C for higher frequencies they are not= =2C =3D > so shielding requirements vary according to the interference. >=20 > For power line interference=2C the electric component can be blocked by = =3D > any metal shield=2C for example the steel skin of sound booth. The =3D > electric component is usually the main culprit=2C and this may be quite = =3D > sufficient to block it. The magnetic component=2C if present=2C is much = =3D > harder to block. Blocking it requires mu-metal shielding as used in =3D > MEG. In practice: (a) install the booth well away from large equipment = =3D > such as elevator motor or transformer station=2C and (b) reduce the =3D > surface of any loops in your cable (e.g. run the electrode leads =3D > together in a bunch). For power line interference=2C a Faraday cage =3D > should not provide any advantage over a metal-skinned booth. I doubt =3D > however that it could make things worse by "trapping interference". >=20 > Radio-frequency EM interference is a bit trickier. You might think it's = =3D > not an issue=2C because EEG amplifiers are equiped with low-pass filters = =3D > with a much lower cutoff. The problem is that high-frequency power can = =3D > be demodulated by nonlinearities=2C for example at the electrode-to-skin = =3D > contact=2C or overloading of the electronics. It's hard to diagnose=2C = as =3D > the interference components in the EEG bear no obvious frequency =3D > relation to the interference itself. You need specialized equipment to = =3D > sample the EM field itself. The Faraday cage should help shield from =3D > this kind of intereference. >=20 > (6) Choose your EEG equipment carefully. Some systems are inherently =3D > less susceptible to interference=2C at least in principle. The Biosemi = =3D > website has pointers to some interesting documents that explain some of = =3D > the issues.=3D20 >=20 > (7) A general recommendation: know your noise. Try to understand it=2C = =3D > before trying to remove it. That should be easier than discovering =3D > what goes on within a listener's brain... >=20 > Alain >=20 >=20 >=20 >=20 >=20 > On 7 Jun 2013=2C at 09:24=2C Massimo Grassi <massimo.grassi@xxxxxxxx> wro= te: >=20 > > Dear list member=2C > >=3D20 > > the question I submitted the other day raised an unexpected response: = =3D > many of the people I came in contact with were actually *unhappy* of the = =3D > electrical shielding of the booth. > >=3D20 > > I quote here the words of Dave Hairston: "While having a fantastic =3D > Faraday cage is theoretically great=2C in reality in can cause as many = =3D > problems as it solves. For instance we have discovered that in many =3D > cases if you have ANY electrical devices inside=2C such as monitors=2C = =3D > keyboards=2C whatever=2C it traps and bounces the power line noise much = =3D > worse than just doing in a normal office room." > >=3D20 > > Here=2C we are definitely going to take some electrical device inside = =3D > the booth. Because the electrical shielding has a cost (about 5000 =3D > euros) I'm now wandering whether it is worth to spend this money. > >=3D20 > > Here comes the question (addressed to those like me that must take =3D > some electrical devices inside the booth): did the electrical shielding = =3D > of your booth improve substantially the quality of your recordings? > >=3D20 > > Thank you all in advance=2C > > m > >=3D20 > > --=3D20 > > http://www.psy.unipd.it/~grassi/ > > http://www.springer.com/978-1-4614-2196-2 > > http://www.finveneto.it/nuoto_schedaatleta.php?id_atleta=3D3D73076 > >=3D20 >=20 > ------------------------------ >=20 > End of AUDITORY Digest - 7 Jun 2013 (#2013-135) > *********************************************** = --_b8227f93-b6bf-478d-a8c3-a2c1a988ed8d_ Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable <html> <head> <style><!-- .hmmessage P { margin:0px=3B padding:0px } body.hmmessage { font-size: 12pt=3B font-family:Calibri } --></style></head> <body class=3D'hmmessage'><div dir=3D'ltr'>Hi Massimo=2C<BR> =3B<BR>I w= orked with an ETS Lindgren room at UC Davis =3Bwith serious shielding. = It blocked mobile phone signals even in the control room about 4 m from the= cage. This is overkill as the brain signals of interest are of a much lowe= r frequency. There were some high frequency =3Boscillation =3Bin th= e EEG with a fundamental around 1.6 kHz=2C =3Bwhich =3Bwhilst not a= n issue for auditory long latency responses=2C became more problematic = =3Bwhen recording at higher sampling rates=2C e.g. for ABR=2C as visible in= :<BR> =3B<BR><blockquote style=3D"margin-right: 0px=3B" dir=3D"ltr"><bl= ockquote style=3D"margin-right: 0px=3B" dir=3D"ltr"><font face=3D"Times New= Roman">=0A= =0A= </font><span style=3D'font-family: "Times New Roman"=2C"serif"=3B font-size= : 12pt=3B mso-fareast-font-family: "Times New Roman"=3B mso-fareast-languag= e: EN-GB=3B mso-bidi-font-weight: bold=3B'>Campbell=2C T.A.=2C Kerlin=2C J.= K.=2C Bishop C.W.=2C &=3B=0A= Miller=2C L.M. (2012). Methods to eliminate stimulus transduction artifact = from=0A= insert earphones during electroencephalography. <i style=3D"mso-bidi-font-s= tyle: normal=3B">Ear &=3B Hearing=2C 33</i>=2C 44-50. doi: </span><a hre= f=3D"http://dx.doi.org/10.1097/AUD.0b013e3182280353"><span style=3D'color: = blue=3B font-family: "Times New Roman"=2C"serif"=3B font-size: 12pt=3B text= -decoration: none=3B mso-fareast-font-family: "Times New Roman"=3B mso-fare= ast-language: EN-GB=3B mso-bidi-font-weight: bold=3B text-underline: none= =3B'>10.1097/AUD.0b013e3182280353</span></a><span style=3D'color: blue=3B f= ont-family: "Times New Roman"=2C"serif"=3B font-size: 12pt=3B mso-fareast-f= ont-family: "Times New Roman"=3B mso-fareast-language: EN-GB=3B mso-bidi-fo= nt-weight: bold=3B'><o:p></o:p></span><BR></blockquote><font face=3D"Times = New Roman">=0A= =0A= </font><BR></blockquote>We also recorded "EEG" =3Bfrom a bucket of salt= water and still =3Bfound the oscillations were still there. <BR> = =3B<BR>So we stripped =3Bthe lab =3Bof equipment and went in with a= n oscilloscope and antenna. Whether using a power source for the oscillosco= pe =3Binside =3Bor outside the =3Bcage=2C there it was=2C the h= igh frequency oscillation. We =3Bcontacted facilities to =3Bverify = if there was a common =3Bground in the control room=2C inside the = =3Bcage and for the cage. =3B =3BApparently there had been a recent= change =3Band the cage had been given =3Ba separate ground. Someth= ing to do with the building being struck by lightning and protecting equipm= ent and people touching that equipment=2C =3Bsuch as an EEG =3Bpart= icipant. =3BThe head of the lab=2C a physicist=2C used the expression o= f =3B"chasing a phantom"=2C =3Bat which point I =3Bvisualised&n= bsp=3Bthe omnipresent =3Bsource of the high frequency oscillation haunt= ing =3Bme day and night=2C and laughing at me. =3BSo the rooms can = have problems and the extent of the problem can vary with what you do in th= e lab. We did not=2C however compare responses inside =3Band outside th= e shielded room=2C as is a =3Bvery interesting =3Bquestion. =3B=  =3B<br><BR>Shielding needs to be grounded for the cage to be effective= . Also=2C it is worth emphasising=2C the ideal is that you have a common gr= ound for all electrical equipment near or in the lab and this is the ground= of the cage=2C assuming you never have a participant connected to electric= al equipment with =3Bthat ground in a thunderstorm. You may be able to = improve the effectiveness of the cage =3Bby the removal of =3Ba gre= en copper oxide that can appear on the =3Bfingers of the door of an ETS= lindgren shielded room. This can be done by regular =3Bcleaning = =3Boff with rubbing =3Balcohol or with a severe =3Bbuild up =3B= sanding with emory paper. This might reduce the hysteresis problem of the c= harge carriers getting trapped that one of the other responses mentioned=2C= as will be particularly severe if the cage is not properly grounded.<br><B= R><div>There is a tendency now to do more EEG research outside of the = =3Bshielded room with many different kinds of EEG system. I have heard = =3Ba =3Bdistributor of a =3Bhigh cost systems with active electrode= s suggest that there were no appreciable signal:noise gain to be found with= a shielded room and such a system. However=2C I know of no systematic inde= pendent =3Bstudy that compares auditory evoked potential signal:noise w= ith such a system inside or outside well-maintained shielding with a common= ground with electrical equipment. It would be of practical and financial s= ignificance to compare the signal-to-noise of evoked potentials recorded wi= th =3Bdifferent EEG systems with passive and active electrodes under th= ese different conditions of no shielding =3Bversus well-maintained shie= lding with a common ground. I'd be very interested what you hear of people'= s experiences.</div><div> =3B</div><div>Best regards=2C</div><div>Tom.<= /div><br> =3B<BR><div>>=3B Date: Sat=2C 8 Jun 2013 00:01:11 -0400<br>= >=3B From: LISTSERV@xxxxxxxx<br>>=3B Subject: AUDITORY Digest - = 7 Jun 2013 (#2013-135)<br>>=3B To: AUDITORY@xxxxxxxx<br>>=3B <br= >>=3B There are 2 messages totalling 153 lines in this issue.<br>>=3B <= br>>=3B Topics of the day:<br>>=3B <br>>=3B 1. Sound proof booth an= d EEG recording [the revenge] (2)<br>>=3B <br>>=3B --------------------= --------------------------------------------------<br>>=3B <br>>=3B Dat= e: Fri=2C 7 Jun 2013 09:24:56 +0200<br>>=3B From: Massimo Grassi &l= t=3Bmassimo.grassi@xxxxxxxx>=3B<br>>=3B Subject: Sound proof booth and = EEG recording [the revenge]<br>>=3B <br>>=3B Dear list member=2C<br>>= =3B <br>>=3B the question I submitted the other day raised an unexpected = response: <br>>=3B many of the people I came in contact with were actuall= y *unhappy* of the <br>>=3B electrical shielding of the booth.<br>>=3B = <br>>=3B I quote here the words of Dave Hairston: "While having a fantast= ic <br>>=3B Faraday cage is theoretically great=2C in reality in can caus= e as many <br>>=3B problems as it solves. For instance we have discovered= that in many <br>>=3B cases if you have ANY electrical devices inside=2C= such as monitors=2C <br>>=3B keyboards=2C whatever=2C it traps and bounc= es the power line noise much <br>>=3B worse than just doing in a normal o= ffice room."<br>>=3B <br>>=3B Here=2C we are definitely going to take s= ome electrical device inside the <br>>=3B booth. Because the electrical s= hielding has a cost (about 5000 euros) <br>>=3B I'm now wandering whether= it is worth to spend this money.<br>>=3B <br>>=3B Here comes the quest= ion (addressed to those like me that must take some <br>>=3B electrical d= evices inside the booth): did the electrical shielding of <br>>=3B your b= ooth improve substantially the quality of your recordings?<br>>=3B <br>&g= t=3B Thank you all in advance=2C<br>>=3B m<br>>=3B <br>>=3B -- <br>&g= t=3B http://www.psy.unipd.it/~grassi/<br>>=3B http://www.springer.com/978= -1-4614-2196-2<br>>=3B http://www.finveneto.it/nuoto_schedaatleta.php?id_= atleta=3D73076<br>>=3B <br>>=3B ------------------------------<br>>= =3B <br>>=3B Date: Fri=2C 7 Jun 2013 11:16:55 +0200<br>>=3B From: = Alain de Cheveigne' <=3Balain.de.cheveigne@xxxxxxxx>=3B<br>>=3B Subjec= t: Re: Sound proof booth and EEG recording [the revenge]<br>>=3B <br>>= =3B A few comments on suggestions so far.<br>>=3B <br>>=3B (1) Patch-pa= nel vs holes. A patch panel is tidy=2C a hole is =3D<br>>=3B future-proo= f. I'd go for the hole=2C as a sound booth is a long-term =3D<br>>=3B in= vestment. It shouldn't have too much impact on acoustic isolation=2C if = =3D<br>>=3B properly designed.=3D20<br>>=3B <br>>=3B (2) The hole. M= ake it large enough to pass the largest expected =3D<br>>=3B connector (e= .g. a UK plug). For a double-walled booth there is little =3D<br>>=3B be= nefit in offsetting the holes in the inner and outer shells=2C because =3D<= br>>=3B this makes little difference at low frequencies. It is important= to =3D<br>>=3B make the holes air-tight after passing the cables. A san= d-box on each =3D<br>>=3B side sounds like an effective solution=2C but p= robably a bit of a hassle =3D<br>>=3B when passing cables. IAC suggests = filling the space around the cables =3D<br>>=3B in the hole with "puggin= g" (compressible foam or clay). For a set of =3D<br>>=3B booths that we= 're ordering=2C I asked them to equip each hole with a box =3D<br>>=3B wi= th screw-on cover to allow the cables to be laid flat for a more =3D<br>>= =3B effective pugging. Someone suggested more than one hole to separate AC= =3D<br>>=3B cables from the rest : good idea.<br>>=3B <br>>=3B (3) A= C power in the booth. If possible=2C ban it. Use filtered DC for =3D<br>&= gt=3B the lights. Don't install AC outlets in the booth (if you need AC at= a =3D<br>>=3B later time=2C you can pass an extension via the hole).=3D2= 0<br>>=3B <br>>=3B (4) Equipment. If possible=2C ban AC-powered stuff = from inside the booth=2C =3D<br>>=3B as well as things such as displays t= hat can produce lots of =3D<br>>=3B electromagnetic interference componen= ts. Equip your booth with a window =3D<br>>=3B such that you can place a= monitor outside visible to the subject.<br>>=3B <br>>=3B (5) Shielding= . There are several things to consider. Major sources of =3D<br>>=3B EM= (electromagnetic) interference are AC power lines=2C electronic =3D<br>>= =3B equipment (computers=2C displays=2C switching power supplies)=2C and ra= dio =3D<br>>=3B waves (e.g. cell phones and cell phone relays). The EM f= ield includes =3D<br>>=3B both an electric and a magnetic component. For= low frequencies (power =3D<br>>=3B lines) the E and M are independent=2C= for higher frequencies they are not=2C =3D<br>>=3B so shielding requirem= ents vary according to the interference.<br>>=3B <br>>=3B For power lin= e interference=2C the electric component can be blocked by =3D<br>>=3B an= y metal shield=2C for example the steel skin of sound booth. The =3D<br>&g= t=3B electric component is usually the main culprit=2C and this may be quit= e =3D<br>>=3B sufficient to block it. The magnetic component=2C if prese= nt=2C is much =3D<br>>=3B harder to block. Blocking it requires mu-metal= shielding as used in =3D<br>>=3B MEG. In practice: (a) install the boot= h well away from large equipment =3D<br>>=3B such as elevator motor or tr= ansformer station=2C and (b) reduce the =3D<br>>=3B surface of any loops = in your cable (e.g. run the electrode leads =3D<br>>=3B together in a bun= ch). For power line interference=2C a Faraday cage =3D<br>>=3B should no= t provide any advantage over a metal-skinned booth. I doubt =3D<br>>=3B = however that it could make things worse by "trapping interference".<br>>= =3B <br>>=3B Radio-frequency EM interference is a bit trickier. You migh= t think it's =3D<br>>=3B not an issue=2C because EEG amplifiers are equip= ed with low-pass filters =3D<br>>=3B with a much lower cutoff. The probl= em is that high-frequency power can =3D<br>>=3B be demodulated by nonline= arities=2C for example at the electrode-to-skin =3D<br>>=3B contact=2C or= overloading of the electronics. It's hard to diagnose=2C as =3D<br>>= =3B the interference components in the EEG bear no obvious frequency =3D<br= >>=3B relation to the interference itself. You need specialized equipmen= t to =3D<br>>=3B sample the EM field itself. The Faraday cage should hel= p shield from =3D<br>>=3B this kind of intereference.<br>>=3B <br>>= =3B (6) Choose your EEG equipment carefully. Some systems are inherently = =3D<br>>=3B less susceptible to interference=2C at least in principle. T= he Biosemi =3D<br>>=3B website has pointers to some interesting documents= that explain some of =3D<br>>=3B the issues.=3D20<br>>=3B <br>>=3B (= 7) A general recommendation: know your noise. Try to understand it=2C =3D= <br>>=3B before trying to remove it. That should be easier than discove= ring =3D<br>>=3B what goes on within a listener's brain...<br>>=3B <br>= >=3B Alain<br>>=3B <br>>=3B <br>>=3B <br>>=3B <br>>=3B <br>>= =3B On 7 Jun 2013=2C at 09:24=2C Massimo Grassi <=3Bmassimo.grassi@xxxxxxxx= IT>=3B wrote:<br>>=3B <br>>=3B >=3B Dear list member=2C<br>>=3B &= gt=3B=3D20<br>>=3B >=3B the question I submitted the other day raised a= n unexpected response: =3D<br>>=3B many of the people I came in contact w= ith were actually *unhappy* of the =3D<br>>=3B electrical shielding of th= e booth.<br>>=3B >=3B=3D20<br>>=3B >=3B I quote here the words of D= ave Hairston: "While having a fantastic =3D<br>>=3B Faraday cage is theor= etically great=2C in reality in can cause as many =3D<br>>=3B problems as= it solves. For instance we have discovered that in many =3D<br>>=3B case= s if you have ANY electrical devices inside=2C such as monitors=2C =3D<br>&= gt=3B keyboards=2C whatever=2C it traps and bounces the power line noise mu= ch =3D<br>>=3B worse than just doing in a normal office room."<br>>=3B = >=3B=3D20<br>>=3B >=3B Here=2C we are definitely going to take some e= lectrical device inside =3D<br>>=3B the booth. Because the electrical shi= elding has a cost (about 5000 =3D<br>>=3B euros) I'm now wandering whethe= r it is worth to spend this money.<br>>=3B >=3B=3D20<br>>=3B >=3B H= ere comes the question (addressed to those like me that must take =3D<br>&g= t=3B some electrical devices inside the booth): did the electrical shieldin= g =3D<br>>=3B of your booth improve substantially the quality of your rec= ordings?<br>>=3B >=3B=3D20<br>>=3B >=3B Thank you all in advance=2C= <br>>=3B >=3B m<br>>=3B >=3B=3D20<br>>=3B >=3B --=3D20<br>>= =3B >=3B http://www.psy.unipd.it/~grassi/<br>>=3B >=3B http://www.spr= inger.com/978-1-4614-2196-2<br>>=3B >=3B http://www.finveneto.it/nuoto_= schedaatleta.php?id_atleta=3D3D73076<br>>=3B >=3B=3D20<br>>=3B <br>&g= t=3B ------------------------------<br>>=3B <br>>=3B End of AUDITORY Di= gest - 7 Jun 2013 (#2013-135)<br>>=3B ***********************************= ************<br></div> </div></body> </html>= --_b8227f93-b6bf-478d-a8c3-a2c1a988ed8d_--