分贝
关于分贝的参考数据和工程信息，用于声学应用。
概述
分贝加权滤波器调整声压测量以匹配人类听觉感知， which is most sensitive in the 1–4 kHz range. The A-weighted filter (dB(A)) is the most common standard for environmental and occupational noise assessment. B and C weighting filters are less frequently used today but provide alternatives for different sound pressure levels and frequencies.
关键公式
Logarithmic Combination of Sound Levels
对数组合两个分贝级的公式。同一原理扩展到多个e sources.
Sound Intensity Level
其中 为参考声强（通常为 W/m²）。
变量
| 符号 | 说明 | 单位 |
|---|---|---|
| Combined sound level | dB | |
| Individual sound levels | dB | |
| Sound intensity level | dB | |
| Sound intensity | W/m² | |
| Reference intensity | W/m² |
Decibel Filter Weighting
声级计应用频率相关的加权滤波器以近似人类听觉响应ponse. The dB(A) filter approximates the 40-phon equal-loudness contour. dB(C) is nearly linear for high sound pressure levels, while dB(B) falls between them and is rarely used in modern practice. The abbreviation "dB(A)" is common engineering shorthand, though SI recommends phrasing like "the A-weighted sound pressure level is x dB."
Frequency Response Data
(dB) | (dB) | (dB) | (dB) | (dB) | (dB) | (dB) | (dB) | |
|---|---|---|---|---|---|---|---|---|
| — | -39.4 | -26.2 | -16.1 | -8.6 | -3.2 | 0 | 1.2 | 1 |
| — | -17 | -9 | -4 | -1 | 0 | 0 | 0 | -1 |
| — | -3 | -0.8 | -0.2 | 0 | 0 | 0 | -0.2 | -0.8 |
来源: engineeringtoolbox.com
Frequency Response of A, B, and C 重量ing Filters
Example: A-Weighted Level Calculation
To find the total dB(A) from octave band measurements, apply the filter correction to each band, then combine logarithmically. Below is a sample calculation:
(Hz) | (dB) | (dB) | 结果ing dB(A) (dB) |
|---|---|---|---|
| 62.5 | 54 | 26 | 28 |
| 125 | 60 | 16 | 44 |
| 250 | 64 | 9 | 55 |
| 500 | 53 | 4 | 49 |
| 1000 | 48 | 0 | 48 |
| 2000 | 43 | -1 | 44 |
| 4000 | 39 | -1 | 40 |
| 8000 | 32 | 1 | 31 |
来源: engineeringtoolbox.com
Comparison of Measured vs. A-重量ed 声音 Levels
To combine the resulting levels logarithmically, pair the highest values and use the combination formula repeatedly. Starting with the two highest bands (250 Hz and 500 Hz):
- Difference: 55 - 49 = 6 dB → Add 1 dB to the higher value: 55 + 1 = 56 dB(A)
- Add next highest (1000 Hz): Difference: 56 - 48 = 8 dB → Add 0.5 dB: 56 + 0.5 = 56.5 dB(A)
- Remaining levels are significantly lower. The total estimated level is ~56.5 dB(A).
A, B and C Weighted Sound Level Calculator
The original page includes spreadsheet-style dB(A), dB(B) and dB(C) calculations. Enter octave-band sound pressure levels below; the calculator applies the weighting corrections and combines the bands logarithmically.
dB(A) Level Adjustment Guidelines
A baseline criterion of 40 dB(A) is commonly adjusted for time, location, and sound character.
(dB) | ||
|---|---|---|
| Time of Day | Evening | -5 |
| Time of Day | Nighttime | -10 |
| Sound Character | Tones or impulsive noise readily detectable | -5 |
| Sound Character | Tones or impulsive noise just detectable | -2 |
| Location | Rural or quiet suburban | 0 |
| Location | Suburban, infrequent traffic | 5 |
| Location | Suburban, medium traffic | 10 |
| Location | Dense traffic or commercial/industrial | 15 |
来源: engineeringtoolbox.com
还原的原始源表
以下表格还原自原始来源页面，以保留完整的参考数据。
Decibel A, B and C
| 31.25 | 62.5 | 125 | 250 | 500 | 1000 | 2000 | 4000 | 8000 | — |
| — | -39.4 | -26.2 | -16.1 | -8.6 | -3.2 | 0 | 1.2 | 1 | -1.1 |
| — | -17 | -9 | -4 | -1 | 0 | 0 | 0 | -1 | -3 |
| — | -3 | -0.8 | -0.2 | 0 | 0 | 0 | -0.2 | -0.8 | -3 |
来源: engineeringtoolbox.com
Decibel A Filter
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | |
|---|---|---|---|---|---|---|---|---|
| Center Frequency (Hz) | 62.5 | 125 | 250 | 500 | 1000 | 2000 | 4000 | 8000 |
| Measured Sound Pressure Level (dB) | 54 | 60 | 64 | 53 | 48 | 43 | 39 | 32 |
| db(A) Filter (dB) | 26 | 16 | 9 | 4 | 0 | -1 | -1 | 1 |
| Resulting Sound Pressure Level dB(A) (dB) | 28 | 44 | 55 | 49 | 48 | 44 | 40 | 31 |
Decibel A - Adjustments to Context
| Character of sound | Tones or impulsive noise readily detectable | -5 |
| Tones or impulsive noise just detectable | -2 | — |
| Time of day | Evening | -5 |
| Night time | -10 | — |
| Neighborhood | Rural and outer suburban areas with little traffic | 0 |
| Suburban areas with infrequent traffic | 5 | — |
| Suburban areas with medium density traffic | 10 | — |
| Suburban areas with some commerce or industry | 10 | — |
| Areas with dense traffic and/or commerce or industry | 15 | — |
| City or commercial areas with very dense traffic and/or bordering industrial areas | 20 | — |
| Industrial areas and/or extremely dense traffic | 25 | — |
来源: engineeringtoolbox.com
工程要点
- The A-weighting filter underestimates low-frequency noise, which can be significant for complaints about HVAC systems, transformers, or traffic rumble.
- C-weighting is often used for peak sound pressure measurements or where low-frequency content is important, such as assessing blast or impact noise.
- When combining levels logarithmically, adding a sound source that is 10 dB lower than the existing level contributes only 0.4 dB to the total—sources 10+ dB below the dominant level are often negligible.
- Regulatory limits typically use dB(A) for environmental noise, but specific applications (e.g., military, industrial) may use other metrics like dB(C) or unweighted dB.
- The SI unit for sound level is the decibel (dB), but it is dimensionless. Always specify the weighting filter (A, B, or C) when reporting.
参考资料
Original Source: engineeringtoolbox.com