Abstract: A low-cut filter is provided which has a frequency response with its low frequency end attenuation limited. The low-cut filter has the effect of increasing effective channel bandwidth while simultaneously allowing low frequency signals from deep within the earth to be included in the output signal. Effective channel bandwidth is increased because low frequency seismic signals are attenuated, automatically allowing channel gain to be increased by a gain ranging amplifier. Increased channel gain automatically amplified the low-amplitude high-frequency end of the spectrum resulting in increased effective bandwidth. A high frequency boost filter is provided whereby the high frequency signal components of the seismic signals may be further relatively amplified thereby enhancing the channel effective bandwidth. The boost filter is provided in the system's input stage in order to keep its effect on system input noise to a minimum.

Abstract: The system for suppressing an ambient noise signal which comtaminates a desired signal includes a noise pickup detector for detecting the ambient noise signal. A noise discriminator processes the detected noise signal into noise data. A reference noise generator converts the noise data into a reference noise signal. The noise generator automatically adjusts the reference noise signal to correspond with changes in the noise signal as it is being detected. A filter filters the reference noise signal into an error signal which is adapted to remove the noise signal from the contaminated signal. A cross-correlator cross-correlates the contaminated signal with the reference noise signal and adjusts the filter to produce the required error signal.