Norsonic nor140 Instructional Manual Download

Page: 174 / 220

156

Chapter 24

Building Acoustics

You are prompted to accept the recalled or meas-

ured values as a part of the averaged result. Press

ENTER

(alternatively

STORE)

to accept or

EXIT

(al-

ternatively

DEL)

if you don’t want to accept. You may

repeat the loading of data to obtain the averaged re-
sults from more measurements. The number of meas-
urements that has been accepted for the averaging is
displayed by a number N. Press the

TBL

key to display

the averaged levels.

Reverberant position Sound Pressure Level

The next set of values to be entered is the sound pres-
sure levels in the reverberant field of the room Lr for
the octave bands in the frequency range 31,5 Hz to 8
kHz. The distance to the corner measurement position
and to any source inside the room should be minimum
1,5 metre, and the height above the floor should be
between 0,5 and 1,5 metre. Two measurement posi-
tions should be measured in the reverberant field with
a distance of minimum 1,5 metre from each other. Re-
call a measurement by using the

RECALL

key or press

START

for starting a measurement. If measured, the

values are automatically stored.

You are prompted to accept the recalled or meas-

ured values as a part of the averaged result. Press

ENTER

(alternatively

STORE)

to accept or

EXIT

(al-

ternatively

DEL

) if you don’t want to accept. You may

repeat the loading of data to obtain the averaged re-
sults from more measurements. The number of meas-
urements that has been accepted for the averaging is
displayed by a number N. Press the

TBL

key to display

the averaged levels.

Reverberation time

The final set of values to be entered is the reverbera-
tion times. The acoustic losses of the receiving room
used in the calculation may be obtained by measur-
ing the reverberation time or by recalling earlier meas-
ured values. See the earlier paragraph under airborne
sound insulation describing measurement of reverber-
ation time. If the optional noise generator is installed
it may be used for the excitation, otherwise impulse
method has to be used. To start a measurement, press

START

when the field cursor is in the field for rever-

beration time marked “T”. After the measurement you
may inspect the resulting reverberation table by press-
ing the

TBL

key.

Please note that the reverberation times are meas-

ured in the octave bands from 63 Hz to 8 Khz. The 31,5
Hz band is not considered according to the ISO 16032
Standard.

Display of results

When the required information has been entered, the
cursor will automatically be placed in the field for cal-
culation of the final result. If you are satisfied with the
entered values press

ENTER

, or if you want to make

any correction, move the field cursor to the required
field and enter the corrected values or press

DEL

clear averaged values.

When you move the field cursor to the field “Calc

results” and press

ENTER

, the following functions are

calculated for both the A- and C-weighted functions:

• The service equipment normalised sound pres-

sure levels L