I used a PIR sensor to activate the noisemaker in a pumpkin. It would react to a person as far as 20 ft away but it's either on or off, no indication how far the target is, also as soon as the target stopped moving it dropped out. Ultrasonic might be better for your purpose. Or maybe you need both.
As to noise, there's the wave shield and there's also a library for playing a wav field directly from the arduino.