This pilot study investigates effects of an ultrashielded capsule at the low-noise underground laboratory (LSBB), Rustrel, France, when used to acquire scalp electroencephalogram (EEG). Analysis of EEG recordings from three volunteers confirms that clean EEG signals can be acquired in the LSBB capsule without the need for notch filtering. In addition, using different setups for acquiring EEG in the capsule, statistical analysis of power spectral densities based on a geodesic distance measure reveals that a laptop and a patient module do not introduce any noise on recorded signals. Moreover, the current study shows that the backward counting task as a mental activity can be better detected using the EEG acquired in the capsule due to the higher level of β-band activities. The counting-relaxed β -band energy ratio is calculated using the S transform and compared between the hospital and capsule, revealing significantly higher values in the capsule (p <; 0.05). Exploring the relative β-band energy (ratio of β-band energy to that of 0-12 Hz in the counting state) reveals that the average of this measure is higher in the capsule for all subjects. Those results demonstrate the potential of the LSBB capsule for novel EEG studies, including the establishment of novel low-noise EEG benchmarks.