The uncertainty of the measurement is 0.001 gm.
The uncertainty in the measurement of a physical quantity is given as how precisely we can measure that, in this case as we can see that the mass of the sodium chloride is precisely given as 29.732 gm, this means the electronic scale is precise to 0.001 gm and round of the values after that which means there is a uncertainty of 0.001 gm.
The vibrations created by noise can be converted to electrical energy through the principle of magnetic Induction, for example by using transducer.
The frequency and period of any wave are reciprocals.
Frequency = 1/period and Period = 1/frequency .
That means that the product of (frequency) times (period) of any wave is always the same. The product is always ' 1 ', with no unit.