Calibration is required before using the sound level meter
The sound level meter is a basic noise measurement instrument, which is a subjective electronic instrument, different from objective electronic instruments such as voltage meters. The ability to convert sound signals into electrical signals can simulate the time characteristics of the human ear's response speed to sound waves; The frequency characteristics with different sensitivities to high and low frequencies, as well as the intensity characteristics that change the frequency characteristics at different loudness levels.
Its working principle is that the microphone converts sound into electrical signals, and then the preamplifier transforms impedance to match the microphone with the attenuator. The amplifier adds the output signal to the weighting network, performs frequency weighting (or external filter) on the signal, and then amplifies the signal to a certain amplitude through an attenuator and amplifier, and sends it to the effective value detector (or external level recorder). The noise level value is given on the indicator head. However, the principles of different types of sound level meters may also vary.
According to the overall sensitivity of sound level meters, there are two methods for classifying sound level meters: one is ordinary sound level meters, which do not have high requirements for microphones. The dynamic range and frequency response flatness range are relatively narrow, and bandpass filters are generally not configured for use in conjunction; Another type is precision sound level meters, which require a wide frequency response, high sensitivity, good long-term stability, and can be used in conjunction with various bandpass filters. The amplifier output can be directly connected to level recorders and recorders, and can display or store noise signals. If the microphone of a precision sound level meter is removed and replaced with an input converter connected to an accelerometer, it becomes a vibration meter that can be used for vibration measurement.
Moreover, there are certain differences in the measurement methods of different sound level meters, but the same is the calibration method of the sound level meter, which involves putting a calibrator on the sound level meter before measurement to obtain a value. The range of values should be 94.0dB plus or minus 0.5dB. If it exceeds this range, the measurement behavior will be invalid.
Why do I need to calibrate a sound level meter before using it
1. Sound level meter measurement is the process of converting the vibration wave signal of the metal diaphragm of the microphone (microphone head) in the front end of the sound level meter into an electrical signal caused by the vibration wave of air vibration caused by the sound signal (sound wave). After being amplified by a dedicated weighing network and circuit operation, the noise decibel value is displayed by digital or electric meter.
2. The quality of air is unstable, such as temperature, humidity, atmospheric pressure, etc., which can change at any time due to environmental and other factors. To ensure the accuracy of the air vibration signal received by the metal diaphragm of the microphone, the sensitivity of the microphone needs to be adjusted accordingly.
3. The process of adjusting the sensitivity of a microphone is to calibrate the sound level meter.
4. The national standard stipulates that "measuring instruments must be calibrated with a sound level calibrator before and after measurement, and the deviation of the calibrated instrument's indication must not exceed 0.5dB, otherwise the test will be invalid.
