An ultrasonic testing system and a wheel to be inspected, the system comprising: one or more matrix array ultrasonic probes; a probe positioning assembly configured to mechanically couple to the one or more matrix array ultrasonic probes and to position the one or more matrix array ultrasonic probes for ultrasonic communication with the wheel which includes a wheel disk forming a center of the wheel, a running tread forming a circumferential outer surface of the wheel, and at least one coupling validation geometry including a feature that reflects ultrasonic beams with defined, characteristic and known reflection properties; wherein the one or more matrix array ultrasonic probes is configured to: emit a validation ultrasonic signal directed towards the coupling validation geometry within the wheel; measure its emitted validation ultrasonic signal after reflection from a respective one of the at least one coupling validation geometry; and emit an ultrasonic inspection signal for measurement of an inspection ultrasonic signal reflected from a defect positioned within an inspection area located between a primary hole positioned about the center of the wheel disk and the running tread of the wheel; and an analyzer configured to: receive the measured validation ultrasonic signal and the measured inspection ultrasonic signal; determine whether the measured validation ultrasonic signal matches a reference validation signal; and output a first notification representing validation of the measured inspection ultrasonic signal under the circumstances that the measured validation signal matches the reference validation signal; wherein the at least one coupling validation geometry comprises the convex intersection from the running tread of the wheel to the wheel disk of the wheel. one or more matrix array ultrasonic probes; a probe positioning assembly configured to mechanically couple to the one or more matrix array ultrasonic probes and to position the one or more matrix array ultrasonic probes for ultrasonic communication with the wheel which includes a wheel disk forming a center of the wheel, a running tread forming a circumferential outer surface of the wheel, and at least one coupling validation geometry including a feature that reflects ultrasonic beams with defined, characteristic and known reflection properties; wherein the one or more matrix array ultrasonic probes is configured to: emit a validation ultrasonic signal directed towards the coupling validation geometry within the wheel; measure its emitted validation ultrasonic signal after reflection from a respective one of the at least one coupling validation geometry; and emit an ultrasonic inspection signal for measurement of an inspection ultrasonic signal reflected from a defect positioned within an inspection area located between a primary hole positioned about the center of the wheel disk and the running tread of the wheel; and an analyzer configured to: receive the measured validation ultrasonic signal and the measured inspection ultrasonic signal; determine whether the measured validation ultrasonic signal matches a reference validation signal; and output a first notification representing validation of the measured inspection ultrasonic signal under the circumstances that the measured validation signal matches the reference validation signal; wherein the at least one coupling validation geometry comprises the convex intersection from the running tread of the wheel to the wheel disk of the wheel. emit a validation ultrasonic signal directed towards the coupling validation geometry within the wheel; measure its emitted validation ultrasonic signal after reflection from a respective one of the at least one coupling validation geometry; and emit an ultrasonic inspection signal for measurement of an inspection ultrasonic signal reflected from a defect positioned within an inspection area located between a primary hole positioned about the center of the wheel disk and the running tread of the wheel; and an analyzer configured to: receive the measured validation ultrasonic signal and the measured inspection ultrasonic signal; determine whether the measured validation ultrasonic signal matches a reference validation signal; and output a first notification representing validation of the measured inspection ultrasonic signal under the circumstances that the measured validation signal matches the reference validation signal; wherein the at least one coupling validation geometry comprises the convex intersection from the running tread of the wheel to the wheel disk of the wheel. receive the measured validation ultrasonic signal and the measured inspection ultrasonic signal; determine whether the measured validation ultrasonic signal matches a reference validation signal; and output a first notification representing validation of the measured inspection ultrasonic signal under the circumstances that the measured validation signal matches the reference validation signal; wherein the at least one coupling validation geometry comprises the convex intersection from the running tread of the wheel to the wheel disk of the wheel.