Ultrasonic alarms can produce false alarms due to which factors?

• A. Excessive air currents
• B. Ultrasonic noise from mechanical equipment
• C. Both A and B
• D. None of the above

Answer: (C)

Ultrasonic detectors work by sending high-frequency sound waves and looking for changes in the echo pattern that indicate movement. Anything that disturbs that clean signal can trigger a false reading. Excessive air currents move objects or create pressure and movement within the detection zone, which alters the ultrasonic reflections and can be mistaken for intrusion. Ultrasonic noise from mechanical equipment introduces additional ultrasonic energy or echoes that mimic movement, also leading to a false alarm. Since either condition can cause erroneous detections, both factors can produce false alarms, making the best choice that both are possible causes.