IEC TR 63079:2017/AMD1:2018
(Amendment)Amendment 1 - Code of practice for hearing-loop systems (HLS)
Amendment 1 - Code of practice for hearing-loop systems (HLS)
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IEC TR 63079 ®
Edition 1.0 2018-09
TECHNICAL
REPORT
AMENDMENT 1
Code of practice for hearing-loop systems (HLS)
IEC TR 63079:2017-04/AMD1:2018-09(en)
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IEC TR 63079 ®
Edition 1.0 2018-09
TECHNICAL
REPORT
AMENDMENT 1
Code of practice for hearing-loop systems (HLS)
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 17.140.50 ISBN 978-2-8322-5928-3
– 2 – IEC TR 63079:2017/AMD1:2018
IEC 2018
FOREWORD
This amendment has been prepared by IEC technical committee 29: Electroacoustics.
The text of this amendment is based on the following documents:
DTR Report on voting
29/983/DTR 29/992/RVDTR
Full information on the voting for the approval of this amendment can be found in the report
on voting indicated in the above table.
The committee has decided that the contents of this amendment and the base publication will
remain unchanged until the stability date indicated on the IEC website under
"http://webstore.iec.ch" in the data related to the specific publication. At this date, the
publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.
_____________
2 Normative references
Replace the existing text of Clause 2 by the following new text:
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
IEC 60118-4:2014, Electroacoustics – Hearing aids – Part 4: Induction-loop systems for
hearing aid purposes – System performance requirements
IEC 60268-16, Sound system equipment – Part 16: Objective rating of speech intelligibility by
speech transmission index
4.1.1 Persons addressed
Replace the existing text of the second bullet point by the following new text:
• designers of HLS and HLS equipment (Clauses 9 and 10, 20, Annex A, Annex C to Annex
G and Annex J),
IEC 2018
10.3.16 Equalization, other than for compensating loop impedance characteristics
Replace the existing third sentence of Subclause 10.3.16 by the following new sentence:
It is likely, therefore, that equalization to compensate for the microphone and auditorium
characteristics can provide a useful improvement in sound clarity and intelligibility (see 10.5
and Annex I for further information).
10.5 Objective measurement of intelligibility
Replace the existing second paragraph of Subclause 10.5 by the following new paragraph:
The recommended procedure is to use the STIPA method (described in IEC 60268-16) with
acoustic input (see Annex I for further information).
Replace the existing title and text of Subclause C.1.1 by the following new title and text:
C.1.1 Magnetic field strength produced by conductor element
By Ampère's rule (also attributed to Laplace, and to Biot and Savart), the magnetizing force
δH at a point P, distance d from a conductor element δx in conductor XL carrying a current I is
given by the following formula:
Iδϕxcos
δ H=
4π d
where
φ is the angle between the line joining the point to the element and the perpendicular from
the point to the line containing the element [see Figure C.1)].
If a is the length of the perpendicular PX, then:
cosϕ= ad
and:
δ
δϕxcos
δϕ=
d
so that:
δ xcosϕ δϕ δϕcosϕ
d da
and:
ϕ
δ HI= δϕcos
4π a
==
– 4 – IEC TR 63079:2017/AMD1:2018
IEC 2018
Add, after the existing Annex H, the following new annexes:
Annex I
(informative)
Measuring STI with hearing loop systems (HLS)
I.1 Causes of loss of intelligibility
As stated in 10.5, it is recommended that the HLS achieves a minimum value for the speech
intelligibility. With a HLS where the recommendations of the IEC 60118-4 are achieved and
with microphone positions close to the source (mouth), an acceptable level of speech
intelligibility is normally attained.
However, particularly in situations where the microphone positions do not correspond to the
recommendations in this document, a m
...
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