What does the weighted weighting of a noise meter mean?
Signal Noise Ratio, also known as Signal to Noise Ratio,
It refers to the ratio of useful signal power to useless noise power. Usually, as power is a function of current and voltage, the signal-to-noise ratio can also be calculated using voltage, 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. Humidity sensor probe, stainless steel electric heating tube PT100 sensor, cast aluminum heater, heating coil fluid solenoid valve
If an amplifier has a high signal-to-noise ratio, it means that the background 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. Below this value, 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 sheet data in many product manuals, there is often an A word, meaning A-weight, which refers to modifying a certain value according to certain rules. Since the human ear is particularly sensitive to the intermediate frequency, if the signal-to-noise ratio in the intermediate frequency band of an amplifier is large enough, even if the signal-to-noise ratio is slightly lower in the low-frequency 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 will be higher than without weighting.
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. A-weighted sound level is currently the most widely used type of noise measurement in the world due to its characteristic curve close to the auditory characteristics of the human ear, while B and C are gradually not 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).
