Various embodiments of the invention include a system having: at least one computing device connected with an array of ultrasonic probes on a gas turbomachine component, the at least one computing device configured to: instruct a first probe in the array of ultrasonic probes to transmit an ultrasonic beam to at least one additional probe in the array of ultrasonic probes; and determine a property of a medium between the first probe and the at least one additional probe based upon a time between transmission of the ultrasonic beam from the first probe and reception of the ultrasonic beam at the at least one additional probe.