Abstract: A system and method for stock-out detection in a retail environment. The method includes sending, from a reference ultrasound emitter, a reference ultrasound pulse that is at least partially reflected by a retail shelf so as to form a return pulse. The return pulse is received at a reference ultrasound receiver. A reference round-trip-delay (RTD) corresponding to a time period between the sending of the reference pulse and the receiving of the return pulse is determined. A monitoring ultrasound pulse is sent toward the retail shelf and a reflection of the monitoring ultrasound pulse is received. A stock-out condition is determined based upon a comparison of the reference RTD and a monitored RTD associated with the monitoring ultrasound pulse.