What is the meaning of "Weighting" on SoundMeter+?
It means frequency weighting. Human ears are sensitive to some frequencies (i.e. [500 Hz, 8 kHz]), but insensitive to others. To simulate ears, frequency weighting is applied to ensure that the measured sound level is what we actually hear.
In total, there are five weightings: A-, B-, C-, D-, and Z-weighting.
The five weightings are defined in International Standards IEC 61672.
Most common weighting is A-weighting. It effectively cuts off lower and higher frequencies. Unit of A-weighted sound level is dBA.
B-weighting gives more weights on low frequencies than A-weighting. Unit of B-weighted sound level is dBB.
C-weighting is usually used for peak measurements and some entertainment noise measurements. Unit of C-weighted sound level is dBC.
D-weighting is specifically designed for measuring high level aircraft noise. Unit of D-weighted sound level is dBD.
Z-weighting is a flat frequency response from 10Hz to 20kHz. It is used to calibrate loudspeakers, home theater systems, and Hi-Fi devices. Unit of Z-weighted sound level is dBZ.