Introduce Several Common Sound Level Meters
The sound level meter is a basic noise measuring instrument, which is a subjective electronic instrument, which is different from objective electronic instruments such as voltmeters. It can convert the acoustic signal into an electrical signal, which can simulate the time characteristics of the human ear's response speed to sound waves; the frequency characteristics of different sensitivities to high and low frequencies, and the intensity characteristics of changing the frequency characteristics at different loudness.
Its working principle is that the microphone converts the sound into an electrical signal, and then the preamplifier transforms the impedance to match the microphone with the attenuator. The amplifier adds the output signal to the weighting network, performs frequency weighting on the signal (or connects an external filter), then amplifies the signal to a certain amplitude through the attenuator and the amplifier, sends it to the effective value detector (or external press level recorder), and gives the value of the noise level on the indicator head. However, the principles of different types of sound level meters will also be somewhat different.
According to the sensitivity of the sound level meter, there are two types of sound level meter classification: one is the ordinary sound level meter, which does not require too much microphone. The dynamic range and flat frequency response range are relatively narrow, and are generally not equipped with a band-pass filter; the other is a precision sound level meter, whose microphone requires wide frequency response, high sensitivity, and good long-term stability, and can be used in conjunction with various band-pass filters. If the microphone of the precision sound level meter is removed and replaced with an input converter and connected to an accelerometer, it becomes a vibration meter for vibration measurement.
Moreover, there are certain differences in the measurement methods of different sound level meters, but the same is the sound level meter calibration method, which is to put the calibrator on the sound level meter before measurement to obtain a value. The range of the value should be 94.0dB plus or minus 0.5dB, beyond this range, the measurement will be invalid.
1. Integral sound level meter - it can directly display the equivalent continuous sound level of the measured noise within a certain measurement time in digital form. For non-stationary noise, it is required to measure the equivalent continuous sound level Leq of the noise, which is defined as: at a certain point in the sound field, use the method of energy averaging within a certain period of time to use several different A sound levels that change intermittently, and use one A sound level to represent the noise level of this period of time.
2. Digital sound level meter - a sound level meter with digital display of measurement results. It not only has the advantages of intuitive and accurate readings, but also can be processed with other analysis and processing instruments and computers through BCD code output.
3. Impulse sound level meter - measure the effective value of the measured signal through the pulsation characteristics of the capacitance at different times, and has a high peak factor capacity, so it can respond to the pulse sound with a short duration and a low repetition ratio. In life, we often encounter discontinuous noise, that is, pulse sound or impact sound, such as typewriter noise, stamping machine noise, guns and so on. This noise is short-lived, may recur for a long time, or even occur only once in a period of time. If it is measured with a general sound level meter, there will be a large error, so a pulse sound level meter should be used.
4. Environmental automatic monitoring (noise statistics, spectrum) analyzer - can automatically collect and calculate noise data according to preset functions, and directly display the results (and store the data at the same time).
