URGENTE: passare da LpA a LpAm

[il_joe]

ciao a tutti
ho la necessità di avere un dato al volo......... è urgentissimo!!!

se ho un valore di pressione sonora calcolato in LpA (ad es. 30) come faccio per calcolarlo in LpAm? (l'unità di misura è DBA?)

per favore, datemi una mano.........

grazie!
ciao

[il_joe]

[Dumah Brazorf]

Google dice:

3.	DEFINITIONS

3.1	Sound pressure level LpA

The sound pressure level LpA is obtained by applying the weighting A to 
the sound pressure level Lp.
The sound pressure level Lp, expressed in dB, of a noise is defined by-

Lp=20 log10 P/Po

Where-
P is the effective sound pressure value measured at a particular point, 
expressed in Pa;
Po is the effective reference sound pressure, equal to 20 x 10-6 Pa.
The value LpA of the A-weighted sound pressure level, expressed in dB(A), 
is obtained by applying the weighting A to the measuring system.

3.2	Measuring surface

The measuring surface of area S (see paragraph 8.3) is a hypothetical 
surface surrounding the sound source and on which the measuring points are 
arranged (see paragraph 6.4).

3.3	Surface sound pressure level LpAm

The surface sound pressure level LpAm is the root mean square of the sound 
pressures recorded on the measuring surface, calculated in accordance with 
the method set out in paragraph 8.4.

http://www.hklii.org/hk/legis/en/reg/cur/400D.txt

[il_joe]

Originariamente inviato da Dumah Brazorf

Google dice:

3.	DEFINITIONS

3.1	Sound pressure level LpA

The sound pressure level LpA is obtained by applying the weighting A to 
the sound pressure level Lp.
The sound pressure level Lp, expressed in dB, of a noise is defined by-

Lp=20 log10 P/Po

Where-
P is the effective sound pressure value measured at a particular point, 
expressed in Pa;
Po is the effective reference sound pressure, equal to 20 x 10-6 Pa.
The value LpA of the A-weighted sound pressure level, expressed in dB(A), 
is obtained by applying the weighting A to the measuring system.

3.2	Measuring surface

The measuring surface of area S (see paragraph 8.3) is a hypothetical 
surface surrounding the sound source and on which the measuring points are 
arranged (see paragraph 6.4).

3.3	Surface sound pressure level LpAm

The surface sound pressure level LpAm is the root mean square of the sound 
pressures recorded on the measuring surface, calculated in accordance with 
the method set out in paragraph 8.4.

http://www.hklii.org/hk/legis/en/reg/cur/400D.txt

ehm... quindi LpAm è il root mean square del LpA.... avendo un LpA di 30 come calcolo il lpAm? E' la radice quadrata media?!?!? che vor dì?
so'gnurante......

[Dumah Brazorf]

E io che ne so!
Spulcia l'intera pagina che magari ci capisci qualcosa, per es al punto 11:

11. METHOD OF CALCULATING THE AVERAGE LEVEL
CORRESPONDING TO THE ROOT MEAN
SQUARE VALUE OF THE VARIOUS
SOUND PRESSURE LEVELS

The root mean square value of the various sound pressure levels resulting 
from a series of measurements made at different points on the measuring 
surface (root mean square in space) can be determined by the following 
formula-

LpAm=LpAo+10log10 1/n	i = n
	 Σ gi
	i = 1
Where-
LpAi = the sound pressure level of the i-th measurement;
LpAo = an auxiliary sound pressure level to simplify the calculation (for 
example, the smallest of the LpAi values);
gi = the auxiliary variable for the i-th measurement-
gi  = 100.1(LpAi-LpAo).