Frequency Weighting of Sound Level Meter
The frequency weighting network in the sound level meter has three standard weighting networks A, B, and C, which are designed according to the response characteristics of the human ear to sound to correct the auditory experience. It attenuates sounds of different frequencies to different degrees according to the equal loudness curve. The A-weighting network simulates the response of the human ear to the 40-square pure tone in the equal-loudness curve. Its curve shape is opposite to that of the 40-square equal-loudness curve, so that the middle and low frequency bands of the electrical signal have greater attenuation. The B-weighting network simulates the human ear's response to the 70-square pure tone, and it attenuates the low-frequency band of the electrical signal to a certain extent. The C-weighting network simulates the response of the human ear to a 100-square pure tone, and has a nearly flat response across the entire audio frequency range.
The sound pressure level measured through the weighting network is no longer the sound pressure level of the objective physical quantity (also called the linear sound pressure level), but the sound pressure level corrected by the sense of hearing, called the weighted sound level. The sound pressure level measured by the sound level meter through the frequency weighting network is called the sound level. The sound level readings obtained from the sound level meter must indicate the measurement conditions. For example, if an A-weighting network is used and the unit is dB, it should be recorded as dB (A). According to the weighting network used, they are called A sound level, B sound level and C sound level respectively, and the units are denoted as dB(A), dB(B) and dB(C). For example, if C weighting is used to measure 70dB data, it should be recorded as 70dB (C) or C sound level 70dB. If A weighting is used to measure 50dB data, it should be recorded as 50dB (A) or A sound level 50dB.
