Table of Content
Noise is almost ubiquitous in daily life, from the sounds of traffic and construction in the early morning to the music or barking of neighbors at night, all of which can affect our quality of life. When these sounds exceed a certain acceptable range, they may constitute noise pollution. Noise pollution refers to environmental sounds that interfere with human health or quality of life, such as traffic noise, industrial noise, or even the low-frequency sound of machinery in an office. The effects of these sounds are not just temporary discomfort; long-term exposure to high-noise environments can lead to increased stress, sleep disorders, and even affect cardiovascular health. Neighbor noise is one of the most common disputes in urban environments, such as footsteps from upstairs neighbors, late-night noise, and excessively loud television or stereo volumes. These problems often lead to disputes between neighbors and may even require complaints to the environmental protection bureau or other relevant agencies to resolve. However, noise problems do not always originate from a single source but are a combination of environmental factors, such as the continuous sound of traffic on the road, factory operations, or even the sound of air conditioning and computer fans in an office. These sounds are called environmental noise.
Another type of sound, though subtle, can still impact specific measurements or working environments: background noise. This refers to persistent, low-intensity noise in the environment, such as the sound of an air conditioner or distant traffic. When measuring noise, the presence of background noise can affect measurement accuracy, masking the true noise source or introducing errors in the data. Therefore, understanding the impact of background noise and adopting appropriate methods for noise measurement and analysis is an important and indispensable topic in modern environmental monitoring.
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Further Reading :How soft is this material? A brief discussion of Shore hardness.
Units of noise
In noise measurement, the most commonly used unit is the decibel (dB), a logarithmic unit used to represent sound intensity or sound pressure level (SPL). The decibel is calculated based on human perception of sound, because our perception of sound intensity is not linear but logarithmic.
Common noise level comparisons:
| Sound pressure level (dB) | Source of sound | Effects on the human body |
|---|---|---|
| 0 dB | Sounds that the human ear can barely hear | No impact |
| 30 dB | A quiet library, whispers | Very quiet |
| 60 dB | General conversation, office environment | Acceptable |
| 85 dB | Busy traffic and factory background noise | Prolonged exposure may affect hearing. |
| 100 dB | Chainsaw, Rock Concert | Hearing may be damaged in a short period of time. |
| 120 dB | Airplane takeoff, alarm sounds | Even short-term exposure can cause pain. |
| 140 dB | Jet engine, explosion sound | Immediately causes hearing damage |
Measurement of equipment noise
When there is significant background noise in the measurement environment, the sound pressure level (SPL) of the device itself must be considered if you want to know the sound pressure level (SPL) when it is operating "itself". Decibels (dB) are expressed logarithmically, and two sound sources do not "linearly add up". Therefore, you cannot simply judge it as "the measured value is equal to the device itself", but you need to make background noise correction.
However, in acoustic practice, the commonly used...Rules of thumbYes: If the difference between the "Measured Total Sound Pressure Level" and the "Background Noise Sound Pressure Level" is significant.10 dB or moreIf the background noise has a negligible impact on the measurement results, then the target sound source is sufficient to "cover" the background noise, and no special background subtraction correction is needed.
Background noise correction
However, if the total measured value and the background valueThe difference is less than 10 dBTherefore, it needs to be done logarithmically.Background subtractionCalculation is necessary to accurately obtain the noise level of the target sound source. The specific calculation method typically uses the following formula:
- L source: The desired sound pressure level (dB) of the "pure target sound source".
- L total: The total sound pressure level (dB) measured when the target sound source and background noise are present simultaneously.
- L background: The sound pressure level (dB) measured when there is only background noise (no target sound source).
When the difference between the two is large enough, the second term (background noise) in the above formula will be extremely small relative to the first term (total sound source intensity), and its influence can be ignored. Conversely, if the difference is not large, the contribution of background noise must be subtracted from the formula to obtain a more accurate result.
Background noise calculation website:
https://www.codecalculation.com/htm/calculate/mechanical/noise/background-correction
