What do you need to pay attention to when monitoring noise_the working principle and application of noise sensor

What do you need to pay attention to when monitoring noise_the working principle and application of noise sensor

The impact of noise on the auditory organs is a process from physiology to pathology. It is necessary to reach a certain intensity and contact time to cause pathological hearing damage. The damage to the auditory organs caused by noise generally develops from temporary hearing displacement to hearing displacement. The harm of noise to the human body is systemic, which can cause changes in the auditory system and affect the non-auditory system. In addition, noise in the workplace can also interfere with language communication, affect work efficiency, and even cause accidents.

In production and life, noise interference is everywhere. In order to ensure people's living environment, relevant departments have standardized corresponding standards to stipulate environmental noise emission limits and measurement methods of industrial enterprises and fixed equipment factories. So what do you need to pay attention to when monitoring noise?

1. The monitoring factor

is generally Ld (equivalent continuous A sound level between eggs), Ln (equivalent continuous A sound level at night), and Lmax must be measured at night when there is sudden noise or occasional noise (Larger A sound level) [Lmax must be written with the preceding qualifying words]

2. Monitoring distribution plan

The general rule is that you can choose to be outside the noise-sensitive building, 1m away from the wall or window, The ground height is above 1.2m.

3. Monitoring time and frequency

Environmental noise monitoring of sensitive buildings should be measured under the normal working conditions of the ambient noise source. According to the operating conditions of the noise source, it is divided into two consecutive periods of day and night. Proceed. According to the characteristics of the environmental noise source, the measurement period can be optimized. Divided into fixed sound source, traffic noise source (mobile sound source).

(1) The influence of fixed sound source

Monitoring time: The equivalent sound level of 1min is measured for steady-state noise, such as Ld measured at 1min during the day and Ln measured at 1min at night. The non-steady-state noise measures the equivalent sound level of the entire working time (or a representative period).

Monitoring frequency: Generally, it is not less than 2 consecutive days of continuous monitoring, 2 times in day and night, that is, 1 time between stars and 1 time at night.

(2) Traffic noise source (mobile sound source)

Monitoring time:

For road traffic, the day and night measurements are not less than the 20min equivalent sound level Leq of the average running density.

For railways, urban rail transit (ground section), and inland waterways, the 1h equivalent sound level Leq, which is not lower than the average operating density, is measured during the day and night. If the urban rail transit (ground section) has a dense operation, The measurement time can be shortened to 20 minutes.

Monitoring frequency:

Generally, it is not less than 2 consecutive days of continuous monitoring, 2 times during the day and night, that is, 1 time during the day and 1 time at night every day.

In noise monitoring, noise sensors are particularly important. Noise sensors are the basis of noise monitoring. The accuracy of noise data monitoring also depends on noise sensors.

The working principle of the noise sensor

The noise sensor has a built-in capacitive electret microphone that is sensitive to sound. One uses air gap and electret as the insulating medium, and uses the back electrode and the metal layer on the electret as two electrodes to form a flat capacitor. There is an output electrode between the two poles of the capacitor. Because there are free charges distributed on the electret film. When sound waves cause the electret film to vibrate and produce displacement; the distance between the two plates of the capacitor is changed, which causes the capacitance of the capacitor to change. Because the number of charges on the electret always remains constant, according to the formula: Qu003dCU, Therefore, when C changes, it will inevitably cause a change in the voltage U at both ends of the capacitor, thereby outputting an electric signal, and realizing the conversion from a sound signal to an electric signal.

Specifically, the total electric charge of the electret is constant. When the plate retreats under acoustic pressure, the capacitance decreases, and the voltage between the two poles of the capacitor increases inversely, and vice versa. When increasing, the voltage between the two poles of the capacitor will decrease inversely proportionally. Then the voltage at both ends of the capacitor is taken out through the field effect with very high impedance, and the noise sensor is amplified at the same time, so that the voltage corresponding to the sound can be obtained. Since the field effect tube is an active device, it needs a certain bias and current to work in the amplified state, therefore, electret microphones must add a DC bias to work.

The noise sensor RS-ZS-N01-* is a high-precision sound measuring instrument. The product uses a high-sensitivity condenser microphone with stable signal and high accuracy. It has the characteristics of wide measuring range, good linearity, easy to use, easy to install, and long transmission distance. The range is as high as 30dB~120dB, which can meet the daily measurement needs, and is widely used in various fields such as home, office, workshop, automobile measurement, industrial measurement and so on.

It can be seen from the report issued by the World Health Organization that noise pollution has become a hidden danger that threatens citizens’ health after air pollution, which is more serious than previously imagined. With the imbalance of urban planning, noise pollution in many cities still cannot be well controlled, but it is believed that with the help of science and technology, the hazards of noise can be lowered and lowered.

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