The Definition and Meaning of Frequency Weighting for Sound Level Meters
It refers to the ratio of useful signal power to useless noise power. Usually measured. Because power is a function of current and voltage, 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 signal-to-noise ratio by power ratio: S/N=10 log Calculate signal-to-noise ratio by voltage: S/N=10 log. Due to the logarithmic relationship between signal-to-noise ratio and power or voltage, to improve signal-to-noise ratio, 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. In electronic circuits, this is not an easy task.
If an amplifier has a high signal-to-noise ratio, it means that the scenery in the north is quiet. Due to the low noise level, many weak sound details hidden by the noise will appear, increasing the floating sound, enhancing the air feeling, and increasing the dynamic range. There is no strict data to determine whether the signal-to-noise ratio of an amplifier is good or bad. Generally speaking, it is best to have a signal-to-noise ratio of about 85dB or higher. If it is lower than the threshold, it may be possible to hear significant noise in music gaps under certain high volume listening conditions. In addition to signal-to-noise ratio, the concept of noise level can also be used to measure the noise level of an amplifier. 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 noise level and signal-to-noise ratio are: the former is a * * *, and the latter is a relative number.
After the specification sheet data in the product manual, there is often an A word, meaning A-weight, which refers to the weighting of a certain value according to certain rules. As the human ear is sensitive to mid frequency objects, 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 than that in 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 weighted A, its value is relatively high when not weighted.
In addition, in order to simulate the different sensitivities of human auditory perception at different frequencies, a network is installed in the sound level meter that can simulate the auditory characteristics of the human ear and correct the electrical signal to approximate the auditory perception. This network is called a weighted network. The sound pressure level measured through a weighted network is no longer an objective physical quantity of sound pressure level (called linear sound pressure level), but a sound pressure level corrected for auditory perception, called weighted sound level or noise level.
