What does noise meter weighting mean?
It refers to the ratio of useful signal power to useless noise power. Usually Bayi measurement, because power is a function of current and voltage, so the signal-to-noise ratio can also be calculated using voltage values, that is, the ratio of signal level to noise level, but the calculation formula is slightly different. Calculate the signal-to-noise ratio based on power rate: S/N=10 log Calculate the signal-to-noise ratio based on voltage: S/N=10 log Since the signal-to-noise ratio has a logarithmic relationship with power or voltage, if you want to improve the signal-to-noise ratio, you must Significantly increase the ratio between the output value and the noise value. For example, when the signal-to-noise ratio is 100dB, the output voltage is 10,000 times the noise voltage. In terms of electronic circuits, this is not an easy task. Humidity sensor probe, , Stainless steel electric heating tube PT100 sensor, , Cast aluminum heater, Heating ring Fluid solenoid valve
If an amplifier has a high signal-to-noise ratio, it means a quiet background. Because the noise level is low, many weak sound details hidden by the noise will appear, which will increase the floating sound, strengthen the sense of air, and increase the dynamic range. There is no strict judgment data to measure whether the signal-to-noise ratio of an amplifier is good or bad. Generally speaking, it is better to have a signal-to-noise ratio of about 85dB or above. If it is lower than this value, it may be heard clearly in the gaps between music in some high-volume listening situations. noise. In addition to signal-to-noise ratio, the concept of noise level can also be used to measure amplifier noise. This is actually a signal-to-noise ratio value calculated using 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 number, and the latter is a relative number.
Behind the specification table data in many product manuals, there is often the word A, which means A-weight, which means A-weighting. Weighting means that a certain value has been modified according to certain rules to weigh the importance. The ear is particularly sensitive to intermediate frequencies, 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 and high frequencies, it will not be easily detected by the human ear. It can be seen that if the weighting method is used to measure the signal-to-noise ratio, the value will definitely be higher than that without the weighting method. In terms of A weighting, its value will be higher than that of no weighting.
In addition: In order to simulate the different sensitivities of human hearing at different frequencies, the sound level meter is equipped with a network that can simulate the hearing 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. rights network. The sound pressure level measured through the weighting network is no longer the sound pressure level of an objective physical quantity (called linear sound pressure level), but the sound pressure level modified by the sense of hearing, called weighted sound level or 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 to 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 degree of attenuation of the low-frequency components of noise. A attenuates the most, B takes the second place, and C attenuates the least. 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. B and C are gradually no longer used.
The noise level reading obtained from the sound level meter must indicate the measurement conditions. If the unit is dB and an A-weighted network is used, it should be recorded as dB (A).
