What is meant by the weighted weighting of noise meters?
Signal Noise Ratio (Signal Noise Ratio), referred to as signal-to-noise ratio or S/N ratio, is the ratio of useful signal power to unwanted noise power.
It is the ratio of useful signal power to unwanted noise power. Usually, because power is a function of current and voltage, the signal-to-noise ratio can also be calculated using the voltage value, i.e., the ratio of the signal level to the noise level, but the calculation formula is slightly different. Calculate the signal-to-noise ratio with the power north rate: S/N = 10 log Calculate the signal-to-noise ratio with the voltage: S/N = 10 log As the signal-to-noise ratio and power or voltage into a logarithmic relationship, to improve the signal-to-noise ratio, then it is necessary to significantly improve the output value and the ratio of the noise value, for example, when the signal-to-noise ratio of 100dB, the output voltage is 10,000 times the noise voltage to the electronic circuits, this is not an easy thing to do. This is not an easy task in terms of electronic circuits.
If an amplifier has a high SNR, it means that the background is quiet, and because the noise level is low, many details of weak tones masked by the noise are revealed, resulting in increased float, airiness, and increased dynamic range. Measurement of the amplifier's signal-to-noise ratio is good or bad without strict judgment data, generally speaking to about 85dB or more for the better, below this value is possible in some loud listening situations, in the music gap in the obvious noise. In addition to the signal-to-noise ratio, measure the amplifier noise size can also use the concept of noise level, which is actually a voltage to calculate the signal-to-noise ratio value, but the denominator is a fixed number: 0.775V, while the numerator is the noise voltage, so the noise level and signal-to-noise ratio, respectively, is: the former is an absolute value, the latter is a relative number.
In many product manuals in the specification table behind the data, there will often be a word A, meaning A-weight, that is, A weighting, weighting means that a certain value according to certain rules weighing the importance of the modification of a certain value, due to the human ear is particularly sensitive to the mid-frequency, so if an amplifier in the mid-frequency band signal-to-noise ratio is large enough then, even if the signal-to-noise ratio in the low-frequency and high-frequency bands slightly lower than the human ear is not easy to detect. It can be seen that if the signal-to-noise ratio is measured using a weighting method, the value will be higher than if no weighting method is used. In the case of A-weighting, the value will be higher than without weighting.
In addition: in order to simulate the human ear hearing at different frequencies have different sensitivity, in the sound level meter is equipped with a can simulate the hearing characteristics of the human ear, the electrical signal is corrected to approximate the value of the network with the auditory sensation, this network is called the weighting network. The sound pressure level measured by the weighting network is no longer the objective physical sound pressure level (called linear sound pressure level), but the sound pressure level corrected by the sense of hearing, called the weighted sound level or noise level.
The weighting network generally has A, B, C. A weighted sound level is simulated by the human ear on the frequency characteristics of low-intensity noise below 55dB, B weighted sound level is simulated by the frequency characteristics of medium-intensity noise from 55dB to 85dB, and C weighted sound level is simulated by the frequency characteristics of high-intensity noise. The main difference between the three is the degree of attenuation of the low-frequency components of the noise, A attenuation is more, B is second, C is the least, A weighted sound level due to its characteristic curve is close to the auditory properties of the human ear, so it is the world's noise measurement in the application of a wide range of B, C has been gradually not used.
The noise level reading from the sound level meter must indicate the measurement conditions, such as the unit is dB, and the use of A-weighted network, it should be recorded as dB (A).
