What can minimize sound interference in Electroencephalography (EEG)?

Minimizing Sound Interference in EEG Recordings

To minimize sound interference in EEG recordings, the most effective approach is to create an enhanced acoustical environment using sound-absorbing materials such as carpet, curtains, and ceiling tiles to reduce background noise while maintaining patient privacy. 1

Environmental Modifications

• Use sound-absorbing materials (carpet, curtains, ceiling tiles) to reduce background noise and increase patient privacy 1
• Reduce loud noise sources in the hospital environment, such as overhead paging and machines 1
• Create a dedicated recording space with walls rather than curtains, as this improves patient comfort and data quality 1
• Consider providing patients with music options through headphones to decrease anxiety, heart rate, and blood pressure during recordings 1

Technical Solutions

• Implement sensor noise suppression techniques that project each sensor signal onto the subspace spanned by neighboring sensors to eliminate sensor-specific noise while retaining signals of interest 2
• Apply appropriate filtering techniques (FIR, IIR, FFT, NOTCH) to eliminate common electrical interference while being mindful that these filters can affect signal latency and amplitude 3
• Use pre-emphasis filtering before recording or digitizing, followed by recovery filtering after playback, which can improve signal-to-noise ratio of high-frequency EEG components by up to 20 dB 4
• Consider independent component analysis (ICA) combined with subspace filtering for more advanced noise reduction in multisensory signals 5

Equipment Considerations

• Standard EEG recording should include 19 electrodes of the 10-20 International System with recording duration of 20-30 minutes to capture variations in vigilance levels 6
• Select appropriate electrode types and design strategies for the initial electronic circuitry front end to improve measurement performance 7
• Be aware that EEG equipment may be subject to electromagnetic interference (EMI) from strong electromagnetic fields, which can affect recording quality 1

Clinical Setting Recommendations

• Maintain a minimum distance from potential sources of electromagnetic interference:
  • Electric motors (30-60 cm) 1
  • Mobile phones (15 cm) 1
  • High-voltage lines (avoid recording platforms near train lines) 1
• Ensure proper shielding when recording in environments with potential electrical interference 1
• Consider continuous EEG monitoring rather than routine EEG when detailed assessment is needed, as routine EEG may miss approximately 50% of abnormal activity compared to prolonged monitoring 6

Pitfalls and Caveats

• Be aware that quantitative EEG algorithms used to support review of recordings may have limitations in noisy environments 1
• Environmental electrical noise may completely obscure EEG in intensive care unit settings, requiring special attention to noise reduction techniques 1
• Avoid relying solely on bispectral index score (BIS) measurements as an EEG quantification tool due to large intra- and inter-individual variability and susceptibility to interference 1
• Remember that while EEG benefits from relative resistance to environmental electrical noise compared to other neurophysiological techniques, proper noise reduction remains essential for accurate interpretation 1

By implementing these environmental modifications, technical solutions, and equipment considerations, sound interference in EEG recordings can be significantly minimized, leading to improved data quality and more accurate clinical interpretation.