[Eeglablist] question about shieldroom specifications

[Archana Singh]

Thanks Makoto, as I understand  (vaguely) these frequency ranges are to
safeguard against radio frequency (RF) interferences that are high in range
of Mhz to Ghz but they interfere the EEG signal at low frequency.
Thanks Valia, the number is not for acoustic shielding - it is a kind of
the measure of shielding  effectiveness is expressed in decibels (dB),
e.g., 40dB means 99% of EM interference blocked.


Archana




On Fri, Oct 17, 2014 at 9:20 AM, Valia Rodriguez <
valia.rodriguez at infomed.sld.cu> wrote:

>
> Hi!
>
> I think it is strange the range of frequencies for filtering and the
> association with dB.
> Could it be that the information provided by the company building was
> making reference to the acoustic isolation for the cage/room?
>
> As far as I know when a shielded room or cage is builded not especific
> filters for electrical frecuencies are used. What it is a requirement is to
> make a good earth and to provide some acoustic shielding. I think the
> values refer to the later.
>
> Valia
>
>
>
>
>
> On 16/10/2014 19:09, Makoto Miyakoshi wrote:
>
> Dear Archana,
>
>  EEG signal range is 1-500Hz. Not even kiloHertz. Because of this, any
> shield room is fine (i.e. does not work anyway).
>
>  The most problematic environmental artifact is 50/60Hz line noise. This
> is hard to shield because of low frequency. I heard that you need a type of
> magnetic shield instead of ordinary copper ones to shut it off.
>
>  I've seen labs that is not shielded. Their data tend to have higher
> 50/60Hz line noise, but we can low-pass the data below that. Our Mobilab
> does not have a shield either.
>
>  > I would like to know what does the cutoff in Hz represent.
>
>  The noise level is guaranteed to be attenuated to the specified levels.
>
>  Makoto
>
>
>
> On Wed, Oct 15, 2014 at 10:20 PM, Archana Singh <sine.arc at gmail.com>
> wrote:
>
>>
>>      Dear All,
>>
>>     I  hope that some of you have experience with construction of
>> electric shielding room for your EEG experiments. I am negotiating with
>> shieldroom companies for our new EEG lab.
>> I would like to know how to interpret the shielding cutoff
>> specifications.
>> I have received various shielding specifications as follows. I know 40dB
>> would be sufficient for our purpose, but I would like to know what does the
>> cutoff in Hz represent.
>>
>>    100K-30MHz / 40dB
>>    10-30MHz  / 80dB
>>     500k-500MHz / 40dB
>>
>>     Best,
>> Archana
>>
>>
>>
>>
>>  __________________________________________
>>   Archana Singh,
>> ERATO Researcher,
>> Functional and Chemosensory brain imaging group
>> Department of Applied Biological Chemistry
>> Graduate School of Agricultural and Life Sciences
>> The University of Tokyo, Tokyo 113-8657
>>
>>
>>
>>
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>
>
>
>  --
> Makoto Miyakoshi
> Swartz Center for Computational Neuroscience
> Institute for Neural Computation, University of California San Diego
>
>
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