515.8-55 analysis of results

Refer to Part One, paragraphs 5.14 and 5.17; and Part One, Annex A, Task 406.

515.8-5 DEFINITIONS

5.1 Sound Pressure Level

The sound pressure level (Lp) is the logarithmic ratio of the sound pressures:

Lp=10 log log 1. 20 log- P Po

Expressed as:

where l0 = reference intensity = 10-12 Wm-2

and $\quad \mathrm{P}_{0}=$ reference pressure $=20 \times 10^{-6} \mathrm{~Pa}$

5.2 Third Octave Filters

The center frequency, f₀, of a third octave filter is:

$\mathbf{f}_{0}=\left(\mathbf{f}_{1} \mathrm{x} \mathbf{f}_{2}\right)^{1 / 2}$

where flower -3 dB frequency

and f₂ upper -3 dB frequency

The relationships between the upper and lower -3 dB frequencies are:

(f₂-f1) = 0.23 fo

₤2=2% f₁

Standard third octave bands are defined in International Specification ISO 266.