IN TIME OF THE SOUND PRESSURE LEVELS MEASURED WITH THE SOUND LEVEL METER AT SLOW AND IMPULSIVE RESPONSE RESPECTIVELY IS TAKEN AS AN INDICATION OF THE IMPULSIVE CHARACTER OF A NOISE . THE SOUND PRESSURE LEVEL OBTAINED WITH THE " IMPULSIVE " RESPONSE IS REFERRED TO AS THE " IMPULSIVE SOUND PRESSURE LEVEL " .
THIS SHALL BE DETERMINED AT ONE OF THE MEASURING POINTS LAID DOWN .
A NOISE IS CONSIDERED TO BE IMPULSIVE IN CHARACTER IF THE DIFFERENCE BETWEEN THE TWO ABOVEMENTIONED LEVELS IS GREATER THAN OR EQUAL TO 4 DB .
7.3.2 . DETECTION OF A NOISE WITH DISCRETE TONES
( 7.3.2 IS BEING REVISED TO TAKE ACCOUNT OF TECHNICAL PROGRESS ; THE FINAL TEXT WILL BE INTRODUCED BY THE " COMMITTEE ON ADAPTATION TO TECHNICAL PROGRESS " PROCEDURE . )
8 . USE OF RESULTS
8.1 . CALCULATION OF ROOT MEAN SQUARE VALUES
8.1.1 . ROOT MEAN SQUARE VALUE AT A MEASURING POINT
THE VALUES OBTAINED FROM THE MEASUREMENTS REFERRED TO IN 7.2 ARE ROOT MEAN SQUARE VALUES IN TIME .
8.1.2 . ROOT MEAN SQUARE VALUE ON THE MEASURING SURFACE
THE LEVEL CORRESPONDING TO THE ROOT MEAN SQUARE VALUE IN SPACE OF THE SOUND PRESSURE LEVELS FOR ALL THE MEASURING POINTS SHALL BE CALCULATED ON THE BASIS OF THE VALUES ESTABLISHED IN ACCORDANCE WITH THE METHOD DESCRIBED IN 8.1.1 .
8.2 . CALCULATION OF AVERAGE EXTRANEOUS NOISE LEVEL
THE AVERAGE EXTRANEOUS NOISE LEVEL OVER THE MEASURING SURFACE IS OBTAINED BY APPLYING THE METHOD DESCRIBED IN 8.1.2 TO THE EXTRANEOUS NOISE LEVELS ESTABLISHED AT THE DIFFERENT MEASURING POINTS .
THE EXTRANEOUS NOISE LEVEL AT A MEASURING POINT IS EQUAL TO THE COMBINED MEAN SQUARE VALUES OF THE SOUND PRESSURES DUE TO BACKGROUND NOISE AND PARASITIC NOISE RESPECTIVELY AT THAT POINT .
8.3 . CALCULATION OF THE AREA S OF THE MEASURING SURFACE
IN THE CASE OF A HEMISPHERE , THE AREA S , EXPRESSED IN M2 , OF THE MEASURING SURFACE IS DETERMINED AS FOLLOWS :
S = 2 PR2
WHERE R = THE RADIUS OF THE MEASURING HEMISPHERE IN M .
IN THE CASE OF A PARALLELEPIPED , THE AREA S , EXPRESSED IN M2 , OF THE MEASURING SURFACE IS DETERMINED AS FOLLOWS :
S = 4 ( AB + BC + CA )
WHERE :
2A = 2D + I LENGHT OF THE MEASURING SURFACE IN M ;
2B = 2D + E WIDTH OF THE MEASURING SURFACE IN M ;
C = D + H HEIGHT OF THE MEASURING SURFACE IN M ;
D DISTANCE SEPARATING THE MEASURING SURFACE FROM THE SOUND SOURCE IN M ;
L LENGTH OF THE SOUND SOURCE IN M ;
E WIDTH OF THE SOUND SOURCE IN M ;
H HEIGHT OF THE SOUND SOURCE IN M .
THE AREA OF THE MEASURING SURFACE MAY BE CALCULATED APPROXIMATELY . IT SHOULD BE NOTED THAT AN ERROR OF MORE OR LESS 20 % IN THIS AREA GIVES A DEVIATION OF MORE OR LESS 1 DB IN THE VALUE