### Strutt Help

Excess Attenuation due to Dense Foliage
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**Strutt|Environmental Noise|Dense Foliage Excess Attenuation** inserts attenuation (dB) into the active row of the worksheet.

Attenuation due to forests and dense foliage can be calculated using ISO 9613-2 or the Hoover formula (Bies and Hansen).

The **Hoover** formula calculates the attenuation using:

`A_f = 0.01 * r_f(m) * f_(1/3)`

Where,

`f` is the frequency of the propagating sound, Hz

`r_f(m)` is the distance of travel through the forest.

The ISO 9613-2 formula calculates the attenuation using the values in Table A.1 (ISO 9613-2). The propagation distance, d_{f}, is calculated as:

References:

- Bies, D., Hansen, C., Engineering Noise Control, p227
- ISO 9613-2 Acoustics - Attenuation of sound during propagation outdoors - Part 2: General method of calculation, p.15

Comments or suggestions to
strutt@arup.com