A point source is emitting sound waves of intensity \( 16 \times 10^{-8}\ \text{W}\ \text{m}^{-2} \) at the origin. The difference in intensity (magnitude only) at two points located at a distance of \( 2\,\text{m} \) and \( 4\,\text{m} \) from the origin respectively will be ______ \( \times 10^{-8}\ \text{W}\ \text{m}^{-2} \).
