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[AUDITORY] Sound proof booth and EEG recording [résumé ]

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Subject: [AUDITORY] Sound proof booth and EEG recording [résumé ]
From: Massimo Grassi <massimo.grassi@xxxxxxxx>
Date: Fri, 7 Jun 2013 08:47:11 +0200
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Dear list members,

below there is the list of all the replies I received. The originalquestion is at the top.

I'm now writing another question to the list because, apparently, notall people here are satisfied by the electrical shielding.


Thanks to those who replied.

m

%%%%%%%%%%%%%
Dear list members,

we are about to buy a IAC soundproof booth and, because here many peopledo EEG recordings, we were thinking to have the booth electricallyshielded. The booth will be used to run psychoacoustics, cognitivescience and neuroscience experiments.

Here comes the problem. What is the best way to carry the EEG-signalfrom the inside of the booth to the outside of the booth?


So far we thought two possible solutions.

1. Place a panel on the booth's wall that has (inside and outside) thespecific plug of the signal cable that comes out of EEG amplifier. Inpractice, we interrupt the signal cable at the booth's wall.2. Make a hole on the booth's wall. The hole starts high in the insideof the booth, runs downward inside the booth's wall and arrives low atthe outside of the booth. I this way the booth is acoustically safebecause the hole is not direct and the EEG-signal cable is notinterrupted, but it needs to be very long (wild guess about 6/8 meters).


Some of my EEG colleagues are unhappy with both solutions because:

1. You interrupt the signal cable and this interruption could introduceartefacts in the EEG-signal.2. The cable is too long and this could introduce artefacts in theEEG-signal.

Is there anybody out there that had this same problem and that cansuggest me which is the best way to solve it?


All the best,
m

%%%%%%%%%%%%%
Classification: UNCLASSIFIED
Caveats: NONE

We are primarily an EEG lab, and recently built a new facility.
Here are my thoughts:
- While having a fantastic Faraday cage is theoretically great, in reality
in can cause as many problems as it solves. For instance we have discovered
that in many cases if you have ANY electrical devices inside, such as
monitors, keyboards, whatever, it traps and bounces the power line noise
much worse than just doing in a normal office room.
The truth is that the latest generation of EEG systems, especially the
wireless and active ones, are soooo much better SNR and less susceptible to
noise that this kind of thing just doesn't matter any more.
- virtually all modern design EEG systems have the ADC on the head and are
broadcasting an already digitized signal to a receiver base, or at least
connect to this base via fiber optic, and from there go to the recording PC
via USB.
Point is... it's all USB digital going through the wall... so there should
be no EEG signal attenuation due to that cable. Only concern will be if it
is too long, the USB may need a small amplification (I believe the limit is
~5-6 meters).

The point of this is, you really only need a USB port on either side of the
wall; possibly a parallel port for signal integration depending on the setup
is laid out but again that is a digital signal.
Now both of these points may be negated if your colleagues are using an
extremely old analog system with wires, a remote ADC rack and such. But to
be frank - given the falling costs and extreme difference in ease of use and
signal quality, it may be cheaper to buy a new EEG system than to get a
fancy room.

In our lab, we built in a massive patch panel with 20-something connectors
(USB, various audio, VGA, DVI, Ethernet, etc). If you go this route plan for
the latest and greatest! But we also left a "hole" behind the panels so we
could run whatever cable we found necessary 5 years from now.

Hope this is helpful,

Dave

------------------------------------------
W. David Hairston, PhD.
Real World Neuroimaging

Translational Neuroscience Branch
Human Research and Engineering Directorate,
U.S. Army Research Laboratory
(410) 278-5925 (office)
william.d.hairston4.civ@xxxxxxxx     * Note, new as of 7/2011

%%%%%%%%%%%%%
Hi Massimo,
I used to have an IAC booth that had a panel with several connectors
(some BNC and some thick stereo jacks). The booth was already
installed when I joined the lab, so I don't know if the panel came
with the booth or if it was installed by Bioacoustics (the contractors
that installed the booth).   I assume that if it is factory installed
it should be designed to not affect the soundproofing.
Good luck with your experiments!

Elena Grassi

%%%%%%%%%%%%%
Hi Massimo,

> we are about to buy a IAC soundproof booth and, because here many people
> do EEG recordings, we were thinking to have the booth electrically
> shielded. The booth will be used to run psychoacoustics, cognitive
> science and neuroscience experiments.
>
> Here comes the problem. What is the best way to carry the EEG-signal
> from the inside of the booth to the outside of the booth?

The answer depends a little on what kind of EEG system you have. If youhave a Brain Products (most models) or a Biosemi EEG system they bothhave fibre optic cables connecting the "head box" to the USB receiver,which in turn is connected to a PC. These fibre optic cables are quitelong and do not introduce or pickup any EM interference. These systemsare even better as the headboxes are battery powered.

If you have a Compumedics/Neuroscan system i.e. a Synamps, Synamps2 orSynampsRT system then options are more limited as the headbox isconnected to the main system via a SCSI type copper cable. The lead onthese is a few metres in length. The main system has a mains plug anddoes not run on batteries. You might be able to get away with shieldedpower points and a shielded USB connection from the main system box tothe EEG recording PC but your mileage may vary on the maximum length ofthe USB cable. You are going to have similar issues with EGI systems(unless it is an MR compatible model),




> So far we thought two possible solutions.
> 1. Place a panel on the booth's wall that has (inside and outside) the
> specific plug of the signal cable that comes out of EEG amplifier. In
> practice, we interrupt the signal cable at the booth's wall.
> 2. Make a hole on the booth's wall. The hole starts high in the inside
> of the booth, runs downward inside the booth's wall and arrives low at
> the outside of the booth. I this way the booth is acoustically safe
> because the hole is not direct and the EEG-signal cable is not
> interrupted, but it needs to be very long (wild guess about 6/8 meters).
>
> Some of my EEG colleagues are unhappy with both solutions because:
> 1. You interrupt the signal cable and this interruption could introduce
> artefacts in the EEG-signal.
> 2. The cable is too long and this could introduce artefacts in the
> EEG-signal.
>
> Is there anybody out there that had this same problem and that can
> suggest me which is the best way to solve it?

We have solved it by using a BrainProducts system.

Thanks.

Bryan.


--
Bryan Paton

PhD candidate
Philosophy Program

School of Philosophical, Historical and International Studies / Schoolof Psychology & Psychiatry


770 Blackburn Rd
Building 220, Rm 141
Monash University
Clayton, VIC, 3168
Australia

+613 990 29790

Research Fellow
EEG Lab Manager
EEG & fMRI, TMS, TMS & EEG Liason
Monash Biomedical Imaging
770 Blackburn Rd, Clayton VIC

http://sites.google.com/site/bryanpaton


%%%%%%%%%%%%%
Massimo

We do something a bit like 1) but requiring a much shorter cable. Wehave a patch panel on the inside and outside of the booth, with a holeat e.g. the bottom both on the inside and outside. We use a removablepiece of foam between the inner and outer walls of the booth asinsulation. The cable runs up one side of this foam piece on the insideand then down it on the other (say 15 cm on each side). Seems to work fine


Bob

Dr. Bob Carlyon
Programme Leader
MRC Cognition & Brain Sciences Unit
15 Chaucer Rd.
Cambridge CB2 7EF
England
Tel: +44 (0)1223 355294
Fax: +44 (0)1223 355294
www.mrc-cbu.cam.ac.uk

MRC Centenary 1913-2013 | 100 years of life-changing discoveries

%%%%%%%%%%%%%
Dear Massimo

We had IAC UK install an adapted double wall booth for EEG a few yearsback. They added some additional screening through having no window inthe door and by electrically bonding all the parts with braiding.We also had DC lighting installed and the facility to kill the ac powerin the room.

For getting EEG/ABR data out of the room had a tube installed throughthe walls to an adjacent booth to take multicore cables. Myunderstanding is that thus tube acts as a waveguide and minimizesinterference.In practice we don't actually use this. Instead we have a Biosemi setupwith the amplifier/converter located inside the room. This is batterypowered and connected through the wall by USB cabling to the PC outside.This kit is working really well for us, for ABR as well as corticalresponses.


I am happy to get you more details if you are interested

Dr Andrew Faulkner
Head of Research Department of Speech Hearing and Phonetic Sciences
UCL (University College London)
Rm 314, Chandler House, 2 Wakefield St
London WC1N 1PF
tel 44 (0)20 7679  4075 (direct)
Internal tel 24075
Fax: +44 (0)20 7679 4238
mailto:a.faulkner@xxxxxxxxx
http://www.ucl.ac.uk/psychlangsci/staff/shps-staff/a_faulkner


%%%%%%%%%%%%%
Dear,

To spend cables through the wall of the booth, I use a U-shaped sandboxwith the two extremities of the U either side of the booth.

You just have to remove the sand, pass the cable and refill with the sand !

By the way, I would be interesting to know how you made your boothelectrically shielded (Faraday cage) ?

Cheers,
Nicolas.

%%%%%%%%%%%%%
Dear colleague,

Being a retired elementary-particle physicist, I know nothing about EEGsignals. In our particle physics lab, however, we frequently transportedelectrical signals over long distances. We used 50-ohm coaxial cables.In the passage of walls, one can use connectors that have the correctimpedance (i.e., 50 ohms); the reflections at these points were found benegligibly small (<10^-3 or so).

Reinhart Frosch,
Dr. phil. nat.,
CH-5200 Brugg.
reinifrosch@xxxxxxxxxx .

Sound proof booth and EEG recording [résumé.eml
Subject:
Sound proof booth and EEG recording [résumé]
From:
Massimo Grassi <massimo.grassi@xxxxxxxx>
Date:
07/06/2013 08:42
To:
AUDITORY@xxxxxxxxxxxxxxx

Dear list members,

below the list of all replies I received. The original question is atthe top.