Question

1. Given a root-mean-square pressure (P_rms) of 0.632 N/m², what is the sound pressure level (SPL)?

Answer 1

Sound pressure level (SpL)
LI = 10 log10

for air: Iref = 10−12 W m2
where Iref is a reference intensity and the standard reference intensity for airborne
sounds is Iref = 10−12 W
m2
. (This is approximately the intensity of barely-audible
pure tone of 1 kHz.)
For travelling and spherical waves I =
p˜
2
rms
%0 c03.3 Sound pressure level
The root-mean-square pressure and sound pressure level for typical noise sources are
given in Table 2.
TABLE 2: RMS pressure and SPL for typical noise sources.
p˜rms SPL
Source (or character) of sound [Pa] [dB]
threshold of pain 100 134
hearing damage during short-term effect 20 ∼120
jet engine, 100 m distant 6–200 110–140
hammer drill, 1 m distant 2 ∼100
hearing damage from long-term exposure 0.6 ∼85
traffic noise on major road, 10 m distant 0.2–0.6 80–90
moving automobile, 10 m distant 0.02–0.2 60–80
TV set (typical loudness), 1 m distant 0.02 ∼60
normal talking, 1 m distant 0.002–0.02 40–60
very calm room 0.0002–0.0006 20–30
calm human breathing 0.00006 10
auditory threshold at 2 kHz 0.00002 0
(dB re 20µPa)

so the answer is for a root-mean-square pressure (Prms) of 0.632 N/m2 is the sound pressure level (SPL) is around 85.