This document summarizes the results of measurements conducted to assess a sound source's compliance with ISO standards for sound power and directivity. Testing was done in accordance with ISO 17025 in a hemianechoic chamber. Results showed a sound power level of 127.0 dBA and A-weighted sound pressure level of 116 dBA. Directivity measurements matched the tolerances specified in ISO 3382 and ISO 16283.

1. OMNI 5”
Dodecahedral sound source
www.ntek.it

2. This paper shows the results of the measurements done to assess the compliance of the sound
sources with the requirements stated in ISO Standards 3744 and 3382 about sound power and
directivity of sound sources.
The entire measurement was conducted following the guidelines provided by the International
Standard Organisation about this kind of tests, in particular the procedure is compliant with
ISO Standard 17025.
Table of contents
Tested Source ........................................................................................ 3
Measuring environment ...................................................................... 4
Measuring equipment .......................................................................... 6
Results ................................................................................................... 7
Sound power ................................................................................. 7
Sound pressure ............................................................................. 8
Directivity ...................................................................................... 9

3. All information subject to change without notice
Tested Source
Model
Omni 5”
Dodecahedral
sound source
Diameter
(mm)
350
Weight (Kg)
12.5
Impedence
(ohm)
3 + 3
Number
of speakers
12
3
The sound source was fed with Pink Noise using an
AMG Mini Digital Amplifier.
During the measurement the sound source was installed
on a rotating device (MB01) free to move on its central
axis for 360° (see Fig. 1).
Fig. 1 Photos of measured source and measurement conditions

4. All information subject to change without notice
Measuring environment
In Figure 2 is reported a simple drawing of the anechoic chamber used for this measurement.
The height of the chamber is 2.63 m.
3530
3170
360
3450
1500
3780
Mic 2
Mic 1
Sound Source
5
0
0
Fig. 2 Mic placement – Mic 1 is for sound power measurement, while Mic 2 is for sound pressure one. Distances in mm
Type Temperature Humidity Pressure
Hemi-Anechoic
Chamber
23 ± 1 ° C 30 ± 15 % 994 ± 10 hPa
4

5. All information subject to change without notice
K1 and K2 correction factor are negligible because of the environment of the measurement
(hemi-anechoic chamber).
The chosen procedure was the one of a high machine with a narrow base due to the assembly of the
sound source (see Source Tested for a reference).
The next tables show the values of L1, L2, L3 and D for this speaker and, hence, the values of A, B, C and S.
Fig. 3 Representation of measurement procedure as indicated in ISO 3744
5
L1 (m) L2 (m) L3 (m) D (m)
0.35 0.35 1.77 0.5
A (m) B (m) C (m) S (m2)
0.675 0.675 2.27 14.0805

6. All information subject to change without notice
Measuring equipment
Device Model Manufacturer Serial number
Sound level meter
Microphone
Preamplifier
Sound Calibrator
Rotating device
NL-52
UC59
NH-25
NC-75
MB-01
Rion
Rion
Rion
Rion
Ntek
00342833
12852
10461
34891821
Ntek Calibration
Lab test tool
The microphone used for the measurement was equipped with a windscreen.
6
To measure the sound source the Rotating device was used in order to “sample” the source every 5° as
stated within the ISO Standard.
The microphone was left in the same position for the entire duration of the measurement.
The data aquired was, then, processed with the help of a dedicated software that, with a proper algorithm,
led to the results indicated in Results section.

7. All information subject to change without notice
Results
In this section are reported the results of the measurements about the sound power of the source and
its directivity.
Lw = 127.0 dBA
Fig. 4 Sound Power Level Spectrum - 1/3 oct
Sound power
0,0
20,0
40,0
60,0
80,0
100,0
120,0
140,0
16
20
25
32
40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
dbA
Frequency (Hz)
7

8. 0,0
20,0
40,0
60,0
80,0
100,0
120,0
16
20
25
32
40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
dBA
Frequency (Hz)
0
0,2
0,4
0,6
0,8
1
1,2
0,0
20,0
40,0
60,0
80,0
100,0
120,0
140,0
16
20
25
32
40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
dB
Frequency (Hz)
All information subject to change without notice
Lp: 116 dBA
Fig. 6 A Weighted Sound Pressure Level – 1/3 octave
Lp linear: 121 dB
Fig. 5 Linear Sound Pressure Level – 1/3 octave
Sound pressure
8

9. All information subject to change without notice
9
Fig. 8 Directivity according to ISO 16283. Upper and lower curves are the ISO 16283 tolerances
-10
-5
0
5
10
100 1000
Directivity
Index
Frequency (Hz)
Fig. 7 Directional response – 1/1 octave
Directivity
0,0
20,0
40,0
60,0
80,0
100,0
120,0
0°
30°
60°
90°
120°
150°
180°
210°
240°
270°
300°
330°
31,5 Hz
63 Hz
125 Hz
250 Hz
500 Hz
1 KHz
2 KHz
4 KHz
8 KHz
16 KHz

10. All information subject to change without notice
Fig. 9 Directivity according to ISO 3382. Upper and lower curves are the ISO 3382 tolerances
-10
-5
0
5
10
100 1000
Directivity
Index
Frequency (Hz)
10

11. Company identity
Ntek is specialized in products and services
for noise and vibration measurement and control,
in all applicable acoustic fields.
The company has been able to improve in designing,
developing and producing solutions that mix
simplicity, portability and user-friendly products
with excellent quality.
Ntek main goal is to supply a qualified service with
a complete range of products delivered on time
in order to guarantee its customers the chance
to focus on their business.
To keep this promise we have strongly invested
in innovation and production process with
monitoring procedures certified by independent
primary authority.
OUR VISION
We believe that acoustics is the basis of wellness
and improvement of life quality.
It’s for this reason that we develop,
innovate and produce equipment inspired
to this philosophy.
HOW WE WORK
Ntek can ensure a high level of service,
thanks to modern processes and new laboratories,
completely equipped for different operations
of design, production, measurement,
check and control.
INTERNAL LOGISTICS AND STOCK
With its new operative location of 500 m2
and
its internal stock, Ntek guarantees available products
in a short time according to customers’ needs.
Today we can handle an order in 48 hours
compared with a standard delivery of 45/60 days.
The new location is structured to be flexible
with logistics activities and in answering efficiently
to productive needs of our customers.
SUSTAINABILITY
Green company, environmentally friendly,
aimed to a continuous improvement
of quality and safety in industrial processes.
Ntek S.r.l.
Via Gabrielli 18
10077 San Maurizio Canavese (TO)
ITALY
www.ntek.it
info@ntek.it
+39 011 40 53 600