EN 60118-4:2015

FOREWORD
INTRODUCTION
1 Scope
2 Normative references
3 Terms and definitions
4 General
5 Using components of a sound system in an induction-loop
   system
6 Meters and test signals
7 Magnetic background noise level of the installation site
8 Characteristics to be specified, methods of measurement
   and requirements
9 Small-volume systems
10 Setting up (commissioning) the system
Annex A (informative) - Systems for small useful magnetic
        field volumes
Annex B (informative) - Measuring equipment
Annex C (informative) - Provision of information
Annex D (informative) - Measuring speech signals
Annex E (informative) - Basic theory and practice of audio-frequency
        induction-loop systems
Annex F (informative) - Effects of metal in the building structure
        on the magnetic field
Annex G (informative) - Calibration of field-strength meters
Annex H (informative) - Effect of the aspect ratio of the loop on
        the magnetic field strength
Annex I (informative) - Overspill of magnetic field from an
        induction-loop system
Bibliography
Annex ZA (normative) - Normative references to
         international publications with their
         corresponding European publications

IEC 60118-4:2014 is applicable to audio-frequency induction-loop systems producing an alternating magnetic field at audio frequencies and intended to provide an input signal for hearing aids operating with an induction pick-up coil (telecoil). Throughout this standard, it is assumed that the hearing aids used with it conform to all relevant parts of IEC 60118. This standard specifies requirements for the field strength in audio-frequency induction loops for hearing aid purposes, which will give adequate signal-to-noise ratio without overloading the hearing aid. The standard also specifies the minimum frequency response requirements for acceptable intelligibility. Methods for measuring the magnetic field strength are specified, and information is given on appropriate measuring equipment (see Annex B), information that should be provided to the operator and users of the system (see Annex C), and other important considerations. This standard does not specify requirements for loop driver amplifiers or associated microphone or audio signal sources, which are dealt with in IEC 62489-1, or for the field strength produced by equipment, such as telephone handsets, within the scope of ITU-T P.370. This third edition cancels and replaces the second edition published in 2006. This edition constitutes a technical revision which includes the following significant technical changes with respect to the previous edition: Addition of Annexes G, H and I where more information is provided about practical considerations and methods of measurement.