In Decibel Adjusted (dBa), the absolute noise
power is evaluated. The noise power denotes the ratio between the disturbing effect of the noise frequency or noise band and a noise power weighting level and refers to a noise power of 3.16 picowatts (pW), which corresponds to a value of -85 dBm
and a dBa value of 0. A 1 kHz tone with a sinusoidal power of 1 mW corresponds to +85 dBa. If the same power is distributed as white noise between 300 Hz and 3.3 kHz over a bandwidth of 3 kHz, the dBa value is +82 dBa due to the frequency weighting.