Answer-Noise is measured in –

The decibel dB is a logarithmic unit that indicates the ratio of a physical quantity usually power or intensity relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities. 230. 4 Bats use echolocation to navigate and forage, often in total darkness. They generally emerge from their roosts in caves, attics, or trees at dusk and hunt for insects into the night.