What should be done if abnormal engine noise is detected during flight?

When abnormal engine noise is detected during flight, investigating for a possible compressor stall is the most appropriate action. A compressor stall can significantly affect the engine's performance and could lead to more severe issues if not addressed promptly. By investigating the source of the abnormal noise, the pilot can assess the engine's condition and determine if further measures, such as changing power settings or diverting the flight, are necessary.

Taking immediate action to understand the cause helps in making informed decisions that ensure the safety of the flight. Ignoring the noise until other indications appear could lead to a delayed response to a potentially critical situation. Reporting to maintenance after landing would not address the immediate concern during flight, and powering down the engine without understanding the issue could lead to loss of control in critical phases of flight. Therefore, investigating the cause of the abnormal noise directly aligns with standard operating procedures aimed at maintaining safety and operational integrity in aviation.