Introduction to Weighting Network of Sound Level Meter
In order to simulate the different sensitivities of human hearing at different frequencies, there is a built-in one that can simulate the auditory characteristics of the human ear and correct the electrical signal to a network that is similar to the hearing. This network is called a weighting network. The sound pressure level measured through the weighting network is no longer the sound pressure level of the objective physical quantity (called linear sound pressure level), but the sound pressure level corrected by the sense of hearing, called the weighted sound level or noise level.
There are generally three types of weighting networks: A, B, and C. The A-weighted sound level is to simulate the frequency characteristics of the human ear to low-intensity noise below 55 decibels; the B-weighted sound level is to simulate the frequency characteristics of 55-85 decibels of moderate-intensity noise; the C-weighted sound level is to simulate the frequency characteristics of high-intensity noise characteristic. The difference between the three is the degree of attenuation of the low-frequency components of the noise. A attenuates the most, followed by B, and C the least. A-weighted sound level is the most widely used noise measurement in the world because its characteristic curve is close to the hearing characteristics of the human ear, and B and C are gradually used. Noise level readings taken from sound level meters must indicate the conditions of measurement.
Amplifiers and Attenuators
At present, many popular domestic and imported amplifiers use two-stage amplifiers in the amplification circuit, namely the input amplifier and the output amplifier, whose function is to amplify the weak electrical signal. The input attenuator and the output attenuator are used to change the attenuation of the input signal and the attenuation of the output signal, so that the pointer of the gauge head points to the appropriate position, and the attenuation of each gear is 10 decibels. The adjustment range of the attenuator used by the input amplifier is the bottom end of the measurement (such as 0~70 dB), and the adjustment range of the attenuator used by the output amplifier is the high end of the measurement (70~120 dB). The dials of the input and output attenuators are often made in different colors, and currently black and transparent are often paired. Since the high and low of many sound level meters are limited by 70 decibels, it is necessary to prevent the limit from being exceeded when rotating, so as not to damage the device.
