On the other hand, the supposedly uncorrelated noise levels of the components add up like orthogonal vectors. The overall dynamic range of the system is therefore always smaller than that of each subsystem. To make best use of the absolute dynamic ranges of the components, the smallest one must be contained in all others. When the dynamic ranges of the sensor and the recorder are of similar magnitude, as is the case with modern broadband sensors and 24-bit digitizers, this condition determines the optimum gain of the sensor within narrow limits.
Similar considerations apply to the seismic input signals.
The earth may in this context be considered as another signal-transmitting system with its own noise and operating range. For a system to resolve ground noise, the sensor must not only have a self-noise below that noise but must also put out the combined ground and sensor noise as an electric signal above the digitizer noise. The necessary gain margin has occasionally been a matter of controversial discussion. Using a larger gain margin would unnecessarily reduce the seismic operating range. A small gain margin does not preclude the extraction of coherent signals from incoherent noise by bandwidth reduction, stacking, or beamforming.