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Hum Bug

Remove noise from electrophysiology recordings without filtering


Electrophysiological signals often become contaminated with line frequency noise originating from power mains, power supplies, and lighting. The Quest Scientific Hum Bug (now under the Digitimer) uses a novel approach to remove electrical interference from signals in real time. The Hum Bug continuously constructs a replica of evolving noise present on the input signal and subtracts this replica from the signal as it passes through the instrument, leaving the physiological signal intact. It performs this function in the presence of biological activity even when noise characteristics evolve over time.

The Hum Bug is not a filter and does not create phase delays, amplitude errors, DC shifts or waveform distortion. Simply connect it between your preamplifier and any analysis equipment and it will automatically eliminate 50/60 Hz. noise and harmonics with frequencies up to several KHz. Noise is eliminated without altering the signal of interest even when frequencies within the signal overlap with noise components. No settings or adjustments are required.

The Hum Bug is effective at removing noise associated with inadequate grounding, ground loops, and electrical pick up. Common applications include noise elimination from signals using microelectrodes, skin electrodes (EKG, EMG, EEG), high gain amplifiers, magnetic sensors and audio equipment.


  • Simple 50/60 Hz Sine Waves
  • Mixtures of 50/60 Hz Harmonics
  • Noise Spikes from Dimmers
  • Complex Noise from Flourescent Lamps
  • No Frequency Loss
  • No DC Voltage Shift
  • No Signal Attenuation
  • No Phase Error
  • All this without waveform distortion

Example electrophysiology traces

Figure (A) A hippocampal recording contaminated with line noise. (B) The physiological signal remains intact as the HumBug removes the imbedded line noise.


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