Combating induction or hearing loop spill

Summary

A loop maker's explanation of how far a hearing loop's magnetic field spills outside the room, and of the array designs it offers to limit spill.

Key findings

• Says the field is fairly even inside a loop but that, outside a simple rectangular perimeter loop, an audible signal can be heard as far as about four times the room's width away.
• Says the field also spreads vertically by roughly the same distance, so it can reach rooms above and below, and that two loops within each other's spill area interfere.
• Names settings where spill matters: adjacent classrooms and lecture theatres, cinemas, and venues with a performance area for electric instruments, where the loop field can interfere with electric guitars, dynamic microphones and some other equipment.
• Presents low-spill and ultra-low-spill array designs, or a cancellation loop, as the ways to contain the field, and says they are more complex to install than a perimeter loop. Its comparison is given as field plots, without measured distances.

Limits

A manufacturer's account, illustrated with plots from its own design tools rather than independent measurements, and promoting its own array products and design service. The page shows no date (its metadata gives first publication on 28 March 2018 and a last change on 17 January 2022).

Read the original

www.ampetronic.com/info-centre/learning-zone/loop-spill-explained

Link checked 9 October 2026. We link to the original and do not host copies.

Cited in

• Auracast, hearing loop, infrared, RF or Wi-Fi: which suits which room?Disputed
• Where do hearing loops fall short: metal, spill, noise and upkeep?Partly answered
• What works in courtrooms, council chambers and other meeting rooms where speech must be heard by all and kept in the room?Partly answered
• What works in hospitals, clinics and pharmacies, where a misheard word can matter most?Partly answered

Cite this source

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