Explain the measurement of norm require for noise criteria (NC) curves in not more than one paragraph

Noise Criteria (NC) curves are standardized measurement metrics used to assess acceptable background noise levels in various environments, particularly in building design and acoustics. These curves are graphically represented on a decibel scale and are derived from laboratory measurements that reflect human perception of noise in relation to different frequencies. The measurement of norm for NC curves involves analyzing sound pressure levels across a range of frequencies, typically from 63 Hz to 8000 Hz, and establishing a contour line that defines the acceptable noise level for specific applications. The NC curves help determine whether a noise environment is suitable for activities such as sleeping, working, or conversing, by ensuring that the background noise is within comfortable limits for human health and productivity.