After the specification table data in many product manuals, there is often a word A, which means A-weight, that is, A-weighting. Weighting means that a certain value has been weighed and modified according to certain rules. The ear is particularly sensitive to mid frequencies, so if an amplifier's mid-band SNR is high enough, the human ear won't be able to detect it, even if the SNR is slightly lower in the low and high frequencies. It can be seen that if the weighting method is used to measure the signal-to-noise ratio, its value will be higher than that without the weighting method. For A-weighting, its value will be higher than that without weighting.
In addition: In order to simulate the different sensitivity of human hearing at different frequencies, there is a network in the sound level meter that can simulate the auditory characteristics of the human ear and correct the electrical signal to a similar value to the sense of hearing. rights network. The sound pressure level measured by the weighting network is no longer the sound pressure level of the objective physical quantity (called the linear sound pressure level), but the sound pressure level corrected by the sense of hearing, which is called the weighted sound level or the noise level.
There are generally three types of weighted networks: A, B, and C. The A-weighted sound level simulates the frequency characteristics of the human ear for low-intensity noise below 55dB, the B-weighted sound level simulates the frequency characteristics of medium-intensity noise from 55dB to 85dB, and the C-weighted sound level simulates the frequency characteristics of high-intensity noise. . The main difference between the three is the attenuation of the low-frequency components of the noise. A attenuates the most, B is the second, and C is 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. B and C are gradually not used.
The noise level reading obtained from the sound level meter must indicate the measurement conditions. If the unit is dB, and an A-weighting network is used, it should be recorded as dB(A).
