Summary
A loop maker's managing director describes testing shortcuts that make a loop look as if it meets IEC 60118-4, and what correct testing involves, in the author's view.
Key findings
- Says some installers measure at very few points, generally next to the loop wire or in a pre-tested seat, and that the signal should instead be measured while walking the whole looped area, including the point farthest from any wire.
- Describes a case in which a maker's representative read only the 1 kHz level at the centre of each loop as proof of frequency response, while an accurate measurement found the response more than 10 dB outside the ±3 dB tolerance; the author adds that measuring within a foot of the wire gives misleading readings.
- Says peak levels in poorly designed loops are often -10 to -15 dB instead of 0 dB ±3 dB, usually because of a perimeter loop or loop widths too far apart, which a more powerful amplifier rarely fixes.
- Gives -32 dB as the IEC limit for background noise but recommends -40 dB, because in the US loop receivers with headphones are also used, and asks that a person without hearing aids listen through a loop receiver before a system is proposed.
- Proposes either "an independently trained and qualified group that certifies hearing loop systems" or that manufacturers, which train installers, help with designs and sell the product, be liable for a working loop and regularly send teams to test their contractors' installations.
Limits
One maker's experience, with anecdotes rather than counted data; the author's company sells loop equipment and installer training. The -40 dB preference is the author's own, and the IEC limit quoted has not been checked here against the paywalled standard. The date is the one printed on the reprint.
Read the original
Cited in
- How is an installed hearing loop checked against IEC 60118-4, and how often does it pass?Partly answered
Cite this source
McKinley R. Best Practices to Install a Hearing Loop System that Meets the IEC Standard. Hearing Loss Association of America (reprinted with permission). 30 September 2021. https://www.hearingloss.org/wp-content/uploads/best-practices-to-install-a-hearing-loop-system-that-meets-the-iec-standard.pdf (accessed 9 October 2026).
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