DELTA - Technical-Audiological Laboratory, Denmark
Presented by Gert Ravn & Allan G. Kristensen
•
>50 years’ experience
•
Independent self-governing foundation
•
Staff 270 (>120 university educated)
•
Turnover 40 Mill USD
•
40% export
•
2500 client assignments/year
DELTA - Technical-Audiological Laboratory
• >40 years of experience in
technical solutions for audiology
• Broad knowledge in all aspects of
audiology
• Widespread international network
• Accredited hearing aid testing IEC/ANSI
– Electroacoustic
– EMC
• Certification of hearing clinics
• Software solutions
Improvement of HA Electro-Magnetic Immunity
through the last nine years
Input Related
Interference Level - IRIL
IRIL values EHIMA Hearing Aid manufacturers Year 1997-2006
40
30
20
Mic. IRIL 800-960 MHz
10
Mic. IRIL 1400-2000 MHz
0
-10
-20
1996
1998
2000
2002
2004
2006
Year
DELTA has carried out IEC 60118-13 hearing aid tests on almost 1000 different
hearing aid types from all international leading manufacturers during the last 10 year´s.
Overall immunity of hearing aids has improved by more than 30 dB !
ANSI C63.19 dipole test – HA part
Advantages
•Test field strength > 200 V/m
•Test freq >3GHz
•Near field test
Disadvantages
•Poor test/retest repeatability
•Expensive setup (shielded room/calibration)
•Time consuming test
•HA shell size matters
•Categorization criteria not documented
•Not widespread in HA industry
•Little experience in test
ANSI C63.19 GTEM / IEC 60118-13 test
Advantages
Disadvantages
•Good test/retest reproducibility
•Limitation's on very high field strength's
•Quicker test
•Test > 3 GHz not possible
•Homogene field (far field)
•Shielded environment not needed
•Widespread in HA industry
•Pass/fail criteria thoroughly documented
•>10 year´s experience in testing
HA GTEM / dipole comparison
Used electromagnetic fieldstrength [dB V/m], at the same
carrier wave frequency (CW), to obtain equal IRIL output from
hearing instrument
60
At equal field strength the GTEM test
method inducts a relative higher IRIL
value than the dipole.
y = 0.8*x + 14.7
55
50
45
40
ANSI
Tolerances on hearing aid immunity
measurements are quite large, but it can
be concluded that the difference is in the
range 5-10 dB.
35
30
25
This difference in field strength will
typically result in an acoustic difference
of 10 – 20 dB IRIL.
20
15
10
10
15
20
25
30
35
40
45
50
55
60
IEC
800 - 950 [MHz], Microphone
1.6 - 2.48 [GHz], Microphone
800 - 950 [MHz], Telecoil
1.6 - 2.48 [GHz], Telecoil
Regresion Line
Suggested test field strength´s for GTEM measurement´s ANSI (M3/T3)and IEC
Frequency range
GHz
0,8 to 0,96 M and T mode
1,4 to 2,0 M and T mode
2,0 to 2,48 M and T mode
>=2,48
Bystander compatibility
Test field strengths
(unmodulated carrier)
for IRIL=55 dB in V/m
>=3,5
>=2
>=1,5
to be considered
User compatibility
Test field strengths
(unmodulated carrier)
for IRIL=55 dB in V/m
>=90
>=50
>=35
to be considered
Field strengths of RF test signals to be used to establish immunity for
bystander compatibility(1 and user compatible hearing aids(2.
The user compatibility level´s is suggested for the ANSI M3/T3 categorisation.
Dipole test has to be carried out for M4/T4 categorisation
Test field strengths in the frequency range above 2,48 GHz will be considered
for use of new generations of digital wireless devices
(1:
Hearing aid users will not be annoyed by interference from bystanders using mobile
phones
(2: Hearing aid users will be able to use mobile phones themselves in most situations