Meaning of weighting of noise meters (sound level meters)
Signal Noise Ratio (SNR) is the ratio of useful signal power to unwanted noise power.
is the ratio of useful signal power to unwanted noise power. It is usually measured in decibels. Since power is a function of current and voltage, the signal-to-noise ratio can also be calculated using voltage values, i.e., the ratio of signal level to noise level, with a slightly different formula. 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 Because the signal-to-noise ratio is logarithmically related to the power or the voltage, it is necessary to improve the signal-to-noise ratio, then it is necessary to significantly increase the output value and the ratio of the noise value, for example: when the signal-to-noise ratio is 100dB, the output voltage is 10,000 times of the noise voltage to the electronic circuits, this is not an easy thing.
An amplifier with a high signal-to-noise ratio means a quieter North View, and because of the low noise level, many details of the weak sounds hidden by the noise will be revealed, resulting in an increase in floating sounds, a stronger sense of air, and an increase in 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 more, and it is possible to hear obvious noise in the music gap in some loud listening situations if it is lower than the warped value. 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 the signal-to-noise ratio of the respectively: the former a ***, the latter is a relative number.
In the product manual in the specification table behind the data, there will often be a A word, meaning A-weight, that is, A weighting, weighting means that a certain value according to certain rules weighing the importance of the modifications, due to the human ear on the mid-frequency objects in particular sensitive, so if an amplifier in the mid-frequency band signal-to-noise ratio is large enough then, even if the signal noise is a little lower than the low-frequency and high-frequency bands, 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 is higher than without weighting.
In addition, in order to simulate the sensitivity of the human ear at different frequencies, there is a network within the sound level meter that can simulate the auditory characteristics of the human ear, correcting the electrical signal to an approximate value of the auditory sensation, and this network is called a 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.
There are generally three kinds of weighting networks, A, B and C. A-weighted sound level is to simulate the frequency characteristics of the human ear for low-intensity noise below 55dB, B-weighted sound level is to simulate the frequency characteristics of medium-intensity noise from 55dB to 85dB, and C-weighted sound level is to simulate the frequency characteristics of high-intensity noise. The main difference between the three is the degree of attenuation of low-frequency components of noise, with A attenuating * more, B the next, and C the least. A-weighted sound level is currently the most widely used in the world's noise measurements due to its characteristic curve being close to the auditory properties of the human ear, while B and C are gradually not used.
