Eeg Contains Excessive Noise - Geodesic Sensor Net Technical Manual

11: Troubleshooting

EEG Contains Excessive Noise

The noise components of an EEG recording have a number of sources. Some noise
originates in the electronics of the amplifier. Problematic noise originates in the
environment in the form of electric and magnetic fields that are picked up by system
components, such as cables, and contaminate EEG signals by being acquired along
with the EEG.
EEG data are susceptible to noise only during recording. After the EEG has been
recorded to disk, it is no longer susceptible to noise contamination.
One way to manage noise is to identify noise generators that may exist in the EEG
recording environment. Another is to be aware that certain ways of positioning
system components can affect the level of noise that is picked up during recording. By
changing the location and orientation of system components, and monitoring the
effect on the amount of noise that the EEG waveforms exhibit, you can reduce or
eliminate the deleterious effects of noise on your EEG recordings.
Noise Generators
Take note of possible noise generators and change the environment accordingly to
reduce noise, per the following sections.
Power Sources
Power cables carry relatively large-amplitude, 50- or 60-Hz electric and magnetic
fields. These transmit noise to nearby cabling.
• Check that there are no power cables near the subject or the interface cable
connecting the GSN to the amplifier.
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Geodesic Sensor Net Technical Manual
S-MAN-200-GSNR-001 • January 31, 2007