It sounds odd. PIR sensors have a relay, which clicks when it opens/closes, but if the electronics have gone wonky, it could be switching on and off rapidly, producing a buzzing or whining sound. Sensors are normally powered by six core cable, one pair for 12 volts power, one pair for the alarm contacts and the remaining pair for tamper. However, this cable is light gauge. If you're referring to the connection box for the alarm panel, this will be fed by mains power, the colours for mains/hot depending on your country. The red may be power if it's an old installation in the UK (old power cable cores were red and black for live and neutral respectively). Might be a good idea to get an alarm installer or electrician to check it out.