How to use the sound level meter correctly to reduce errors?
Sound level meter, also called decibel meter, is the most commonly used instrument in acoustic measurement. It can measure the noise level of industrial noise, traffic noise, environmental noise and living noise, etc., based on the hearing characteristics of the human ear. Suitable for measurements of environmental noise, electromechanical product noise, traffic noise, architectural acoustics and electroacoustics.
A sound level meter generally consists of a microphone, amplifier, attenuator, weighting network, detector, indicator meter and power supply. Delicate and expensive components like microphones are relatively easy to damage. In order to measure more accurately and better maintain the sound level meter, you need to pay attention to the following matters:
1. Before use, you should read the instruction manual to understand the usage and precautions of the instrument. Preheat according to the preheating time specified in the sound level meter instruction manual.
2. When measuring sound levels outdoors, the wind noise on the microphone when the air flows will cause measurement errors, because the signal to be measured (noise source) and the wind noise will be superimposed. Please install a windproof ball on the microphone head to prevent the microphone from being directly blown by the wind and causing airflow noise.
3. The sound level meter is powered by batteries. Check whether the battery voltage meets the requirements. If the battery voltage is insufficient, replace it. Please remove the battery if not used for a long time to avoid electrolyte leakage and damage to the instrument.
4. First of all, the sound level meter has been calibrated before leaving the factory. However, if the instrument has not been used for a long time, in order to ensure measurement accuracy, it is recommended to use a calibrator to recalibrate. Calibration method: For the convenience of calibration, the microphone must be rotated when the calibrator is fixed. Start the sound level meter and set it to a measurement range of 50-100dB with time weighting of "Fast" and frequency weighting of "A". Move the switch to the neutral position (94dB) to activate the calibrator. If the sound level meter deviates from the displayed value, readjust it using the provided adjustment screwdriver. Then check whether the second sound level of the calibrator is also within the ±0.2dB error range. Please note that to complete this operation you must first select the corresponding measurement range (80-130dB).
The housing of the instrument and the person operating it may not only block sound from a certain direction, but may also create reflections that can lead to serious measurement errors. Experiments have shown that, for example, when measurements occur within less than 1m of the human body, the human body may cause errors of up to 6dB at a frequency of 400 Hz. At other frequencies, this error may be smaller. It is generally recommended to place the instrument at least 30 cm from the human body - 50cm is better. When measuring, the instrument should select the correct gear according to the situation. Hold both sides of the sound level meter flatly with both hands, and the microphone points to the sound source being measured. You can also use extension cables and extension rods to reduce the influence of the appearance of the sound level meter and the human body on the measurement. .
6. When you do not know how big the sound level is to be measured, you must place the "attenuator" at the maximum attenuation position, and then gradually adjust it to the attenuation position required by the measured sound level during measurement to prevent the measured sound level from exceeding the range. Damage to the sound level meter.
7. Do not disassemble the instrument without authorization and prevent it from being thrown or dropped.
8. The instrument should avoid being placed in places with high temperature, humidity, sewage, dust, air or chemical gases containing high concentrations of hydrochloric acid and alkali.
