The Meaning of Weighted Weighting of Sound Level Meters
Signal Noise Ratio (SNR)
It refers to the ratio of useful signal power to useless noise power. Usually measured in beta. Because power is a function of current and voltage, the signal-to-noise ratio can also be calculated using voltage values, which is the ratio of signal level to noise level. However, the calculation formula is slightly different. Calculate signal-to-noise ratio based on power ratio: S/N=10 log Calculate signal-to-noise ratio based on voltage: S/N=10 log Due to the logarithmic relationship between signal-to-noise ratio and power or voltage, it is necessary to significantly increase the ratio of output value to noise value. For example, when the signal-to-noise ratio is 100dB, the output voltage is 10000 times the noise voltage. For electronic circuits, this is not an easy task.
If an amplifier has a high signal-to-noise ratio, it means that the north view is quiet. Due to the low noise level, many weak sound details masked by noise will appear, resulting in increased floating sound, enhanced air sense, and increased dynamic range. There is no strict discrimination data for measuring whether the signal-to-noise ratio of an amplifier is good or bad. Generally speaking, it is better to be around 85dB or above. If it is below the threshold, it is possible to hear obvious noise in music gaps during certain loud listening situations. In addition to signal-to-noise ratio, the concept of noise level can also be used to measure the noise level of amplifiers. 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 the noise voltage. Therefore, the difference between noise level and signal-to-noise ratio is: the former is an absolute number, while the latter is a relative number.
After the specification table data in the product manual, there is often an A word, meaning A-weight, which means A weight. Weight refers to modifying a certain value according to certain rules. Due to the sensitivity of the human ear to intermediate frequency objects, if the signal-to-noise ratio of an amplifier in the intermediate frequency band is large enough, even if the signal-to-noise ratio is slightly lower than the low and high frequency bands, it is not easy for the human ear to detect. It can be seen that if the weighting method is used to measure the signal-to-noise ratio, its value will definitely be higher than if the weighting method is not used. In terms of A weighting, its value is higher without considering the weight.
In addition, in order to simulate the different sensitivities of human auditory perception 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 approximate the auditory sensation. This network is called a weighted network. The sound pressure level measured through a weighted network is no longer an objective physical quantity (called linear sound pressure level), but a sound pressure level corrected by auditory perception, called weighted sound level or noise level.
There are generally three types of weighted networks: A, B, and C. A-weighted sound level simulates the frequency characteristics of low intensity noise below 55dB in the human ear, B-weighted sound level simulates the frequency characteristics of medium intensity noise from 55dB to 85dB, and C-weighted sound level simulates the frequency characteristics of high intensity noise. The main difference among the three is the degree of attenuation of the low-frequency components of the noise, with A having the most attenuation, B taking second place, and C having the least. Due to its characteristic curve close to the auditory properties of the human ear, A-weighted sound level is currently widely used in noise measurement in the world, while B and C are gradually not used.
