For the low frequency noise the A-weighted level of the noise in the frequency
range 10 – 160 Hz is regarded, the symbol used is LpA,LF. The recommended limits
are 5 – 15 dB lower than the ordinary noise limits, and the lowest recommended
limit LpA,LF = 20 dB has a close connection with the infrasound limit LpG = 85 dB
as illustrated in Figure 3.