Two mobile phone, A and B, are placed on the top of a wooden desk without direct contact, the gap between these two phones is about 5 centimeters.
When A is vibrating, e.g., a call comes in, a time series data is captured by B's accelerator sensor, which represents the acceleration in x, y, and z axis.
After transforming this time series data into frequency domain, I notice there is a significant power around 22 Hz.
Besides, from some paper, I have read a statement：
“If an object is struck by a rod, it will vibrate at its natural frequency no matter how hard it is struck. The magnitude of the strike will increase the amplitude of vibration, but not its frequency...if a periodic force is applied at the same natural frequency of the object, the object exhibits amplified vibration – resonance.”
If this is true, does it suggestion the 22 Hz is the natural frequency of wooden desk? or it is just the vibration frequency of phone A? or even the resonance frequency of phone A?