An acoustic measurement system for detecting locked blade assemblies in a gas turbine having a plurality of blade assemblies. The system includes at least one acoustic sensor for detecting acoustic energy generated as a result of movement of the blade assemblies during a turning gear operation. In addition, the system includes a housing for holding the acoustic sensor, wherein the housing is mounted to an outer diffuser of the gas turbine. The housing also includes a rotatable joint for enabling rotation of the acoustic sensor. Further, the system includes a data acquisition unit that detects an absence of acoustic energy wherein the absence of acoustic energy is indicative of locked blade assemblies. The blade assemblies are locked due to wedging of a sealing pin between the blade assemblies. The acoustic energy is detected in a frequency range of approximately 0.9 kHz to 10 kHz.