In modern industry, architecture, transportation and daily life, noise has become an important factor affecting people’s health and quality of life. In order to effectively control noise pollution, it is particularly important to carry out noise testing scientifically. So, how is the noise measured? This paper will briefly introduce the basic principle, measuring tools, measuring methods and matters needing attention of noise testing.
First, the basic principle of noise testing
Sound is a mechanical wave generated by the vibration of an object, which propagates to the human ear through air, water or solid. Noise refers to those unwelcome and disturbing sounds. The core of noise testing is to measure the intensity of sound waves, usually in decibels (dB). The higher the decibel value, the louder the sound. The range of sound pressure level perceived by human ears is roughly between 0 dB (hearing threshold) and 120-140 dB (pain threshold).
Second, the commonly used measuring tools
The main tool for noise testing is the Sound Level Meter (SLM). It is a special instrument for measuring the intensity of environmental noise, which can convert sound waves into electrical signals, amplify, filter, weight and display them. Modern sound level meters usually have three kinds of frequency weighting networks: A, B and C, among which A weighting (dB(A)) is the most commonly used, because it simulates the sensitivity of human ears to sounds of different frequencies.
In addition, some high-end sound level meters also have real-time spectrum analysis function, which can provide the frequency composition of noise and facilitate further analysis of noise sources.
Third, the common measurement methods
1. Field measurement method
In practical environment, such as factory, construction site, roadside or indoor space, the sound level meter is placed in a representative position for measurement. In order to ensure the accuracy of the data, the measuring point should be prevented from being affected by reflected sound, wind or electromagnetic interference.
2. Time weighted measurement
The noise level often changes with time, so it is necessary to make an average measurement within a certain period of time, for example, using the equivalent continuous A sound level (LAeq) to represent the average noise level within a certain period of time.
3. Spectrum analysis
For complex noise sources, such as mechanical equipment and vehicles, spectrum analysis is needed to identify the main noise frequency components, which is helpful to take targeted noise reduction measures.
IV. Matters needing attention in measurement
-Choose a suitable measuring position: generally, it should be 1-1.5 meters away from the ground and 1 meter away from the wall or other reflecting surfaces.
-Avoid interference sources: interference from other irrelevant noise sources should be excluded as far as possible during measurement.
-Pay attention to weather conditions: wind, rain and other weather will affect the sound wave propagation, so we should try our best to measure it under suitable weather conditions.
-Calibrate the instrument regularly: before and after each measurement, the sound level meter should be calibrated with standard sound sources to ensure the accuracy of the measured data.
V. Summary
Noise test is an important means to evaluate the environmental noise level, which is of great significance to environmental protection, occupational health and architectural design. Through scientific and reasonable measurement methods and techniques, we can more accurately grasp the noise distribution and provide the basis for making noise control measures. With the development of technology, the future noise testing will be more intelligent and automatic, which will help us better deal with the noise pollution problem.
(Full text: about 680 words)