Define the detection threshold and the impact of the noise floor.

• A. The detection threshold is the level below which a signal is declared present; a higher noise floor has no effect on detection.
• B. The detection threshold is the level below which a signal is declared present; a higher noise floor increases detection probability.
• C. The detection threshold is the level above which a signal is declared present; a higher noise floor lowers detection probability for weak signals.
• D. The detection threshold is the ratio of signal to noise required for detection.

Answer: (C)