I hope that the aircraft and ships are recording their reception of the 37.5 khz frequency and time stamping it because later computer analysis using methods such as outlined above could pull out signals that are not audible to the human ear.
Its called intergrating, and doing it in a cyclic fashion on a known period is called folding your data in pulsar speak. Its all fairly basic signal analysis that the people doing the searching will know about.
The guys/gals out there are generally profesionals and will know most techniques and when to apply them. Yes occasionally there are Darwin moments, but not usually.