Answer:
correct fill up is natural frequency
Explanation:
solution
Vibration is a mechanical phenomenon and vibrating any object it will create the disturbance, it may be vocal cord of a person and any object that is vibrating, it will create sound and Decibel dB is unit which is use to measure the intensity of sound
All the object having natural frequency at which they vibrate
and frequency at which object tends to vibrate with when hit or plucked or struck or if some how it disturb, that is natural frequency
so correct fill up is natural frequency
