What does the noise meter's weighted weighting mean?
It is the ratio of the useful signal power to the unwanted noise power. Usually, because power is a function of current and voltage, the signal-to-noise ratio can also be calculated by using the voltage value, that is, the ratio of the signal level to the noise level, but the calculation formula is slightly different. Calculate the signal-to-noise ratio by power ratio: S/N=10 log Calculate the signal-to-noise ratio by voltage: S/N=10 log Since the signal-to-noise ratio has a logarithmic relationship with power or voltage, it is necessary to increase the signal-to-noise ratio Greatly improve the ratio of output value to noise value. For example, when the signal-to-noise ratio is 100dB, the output voltage is 10,000 times the noise voltage. This is not an easy task for electronic circuits.
If an amplifier has a high signal-to-noise ratio, it means that the background is quiet. Due to the low noise level, many details of weak sounds covered by noise will appear, which will increase floating sound, enhance the sense of air, and increase the dynamic range. There is no strict judgment data to measure whether the signal-to-noise ratio of the amplifier is good or bad. Generally speaking, it is better to be above about 85dB. If the value is lower than this value, it is possible to hear obvious noise in the music gap under certain high-volume listening conditions. noise. In addition to the signal-to-noise ratio, the concept of noise level can also be used to measure the noise level of the amplifier. This is actually a signal-to-noise ratio value calculated by voltage, but the denominator is a fixed number: 0.775V, and the numerator is Noise voltage, so the difference between noise level and signal-to-noise ratio is: the former is an absolute value, and the latter is a relative number.
Behind 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 modified according to certain rules. The ear is particularly sensitive to mid-frequency, so if the signal-to-noise ratio of an amplifier in the mid-frequency band is large enough, even if the signal-to-noise ratio is slightly lower in the low-frequency and high-frequency bands, the human ear will not be able to detect it. It can be seen that if the weighting method is used to measure the signal-to-noise ratio, the value will be higher than that without the weighting method. In terms of A-weighting, its value will be higher than that without weighting.
Another: In order to simulate the different sensitivities of the human ear at different frequencies, a sound level meter is equipped with a network that can simulate the auditory characteristics of the human ear and correct the electrical signal to an approximate value of the sense of hearing. This network is called a meter right 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 that has been 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 simulates the frequency characteristics of the human ear to low-intensity noise below 55dB, the B-weighted sound level simulates the frequency characteristics of moderate-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 degree of attenuation of the low-frequency components of the noise. A has the most attenuation, followed by B, and C has the least. The A-weighted sound level is the most widely used in 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.
The noise level readings obtained from the sound level meter must indicate the measurement conditions. If the unit is dB and the A-weighting network is used, it should be recorded as dB (A).
