Malaysian Airlines MH370 contact lost

[Machinbird]

Each of the transmissions on April 8 were intermittent and at a frequency of around 27 kHz—much lower than the 37.5 kHz frequency that beacons are designed to emit, and also lower than the 33.3 kHz frequency of other transmissions on April 5. "As far as frequency goes, between 33 kHz and 27 kHz is a pretty large jump," Cmdr. Lybrand said."

The degradation of supply voltage (such as when batteries become exhausted) is known to have effects on oscillation frequency of crystal oscillator circuits including oscillations in other modes.

The pingers are essentially variants of crystal oscillator circuits. Has anyone seen any data about actual pinger frequency performance as the batteries approach exhaustion? It would seem reasonable that the manufacturers would have run these tests already.