The flight accelerometer data was measured on a launch vehicle which shall remain anonymous. This was due to an oscillating thrust vector control (TVC) system during the burn-out of a solid rocket motor. This created a “tail wags dog” effect. The resulting vibration occurred throughout much of the vehicle.
The oscillation frequency was 12.5 Hz with a harmonic at 37.5 Hz.
The mission was nevertheless successful, but perhaps barely so.
I discovered the anomaly and alerted the guidance and control engineers who remained skeptical but who finally admitted the problem.
Further information is given at: Vibrationdata Rocket Page
– Tom Irvine