How may the accuracy be reduced when correctly utilizing the sound level meter?
Sound level meter, also called decibel meter, noise 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 according to the auditory characteristics of human ears. It is suitable for the measurement of environmental noise, mechanical and electrical product noise, traffic noise, architectural acoustics and electroacoustics.
1. Turn on the power switch, and set the range switch to an appropriate position according to the volume of the measured sound.
2. Select the measurement mode (A/C) and measurement unit (decibel or loudness unit) according to your needs.
3. To measure the real-time sound level, select "FAST (fast)"; to measure the average sound level, select "SLOW (slow)".
4. For night measurement, the backlight of the display can be turned on.
5. If the display shows "UNDER" or "OVER", you should move the range switch up ▲ or down ▼ at this time, if the "UNDER" or "OVER" sign still cannot disappear, it means that the measured sound level exceeds the measurement scope.
6. After adjusting the range of the sound level meter, you can read the measurement result from the display. You can press the "MAX" key to read the maximum sound level.
7. After measuring, turn off the power switch.
A sound level meter generally consists of a microphone, an amplifier, an attenuator, a weighting network, a detector, an indicator head, and a power supply. Delicate and expensive parts such as microphones are relatively fragile. For more accurate measurement and better maintenance of the sound level meter, the following items need to be paid attention to:
1. Read the instruction manual before use to understand the use method and precautions of the instrument. Preheat according to the preheating time specified in the instruction manual of the sound level meter.
2. In the occasion of measuring the sound level outdoors, the wind noise on the microphone will cause measurement errors when the air flows, because the signal to be measured (noise source) and the wind noise will be superimposed together. 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 take out the battery if it is not used for a long time to avoid electrolyte leakage and damage to the meter.
4. First of all, the sound level meter has been calibrated before leaving the factory, but if the instrument has not been used for a long time, in order to ensure the measurement accuracy, it is recommended to use a calibrator to re-calibrate. Calibration method: For the convenience of calibration, the microphone should be rotated when the calibrator is fixed. Start the sound level meter, then set it to the 50-100dB measurement range, time weighting to "Fast" and frequency weighting to "A". Move the switch to the middle position (94dB) to activate the calibrator. If the sound level meter deviates from the displayed value, readjust using the adjustment screwdriver provided. Then check whether the second sound level of the calibrator is also within the error range of ± 0.2dB. Please note that the corresponding measurement range (80-130dB) must be selected first to complete this operation.
5. The shell of the instrument and the person operating the instrument may not only block the sound from a certain direction, but may also produce reflections, resulting in serious measurement errors. Experiments have shown, for example, that the human body can cause an error of up to 6dB at a frequency of 400 Hz when the measurement takes place within less than 1m of the human body. At other frequencies, this error may be smaller. It is generally recommended to place the instrument at least 30 cm away from the human body - 50 cm is better. When measuring, the instrument should select the correct gear according to the situation, hold both sides of the sound level meter flat with both hands, and the microphone points to the sound source to be measured. Extension cables and extension rods can also be used to reduce the impact of the appearance of the sound level meter and the human body on the measurement. .
6. When the measured sound level is not known, the "attenuator" must be placed at the maximum attenuation position, and then gradually adjusted 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 to prevent throwing.
8. The instrument should not be placed in a place with high temperature, humidity, sewage, dust, air or chemical gas with high content of hydrochloric acid and alkali.
