Listen Technologies HLS-2D – Metal Loss Test Driver

Product Overview

The Listen Technologies HLS-2D is a metal loss test driver used during hearing loop site survey to measure how much magnetic field strength a building's structure will absorb. Steel decking, reinforcement and structural framing all attenuate the field a hearing loop produces, and the loss varies enough between buildings that it cannot be assumed. This instrument quantifies it before the loop driver current rating is fixed.

Product Description

Metal loss is the variable that most often turns a hearing loop installation into a remedial job. A loop designed for a nominal floor area will fail its IEC 60118-4 measurement if the structure absorbs more field than the design assumed.

The HLS-2D drives a test loop on site so the resulting field can be measured against what the same loop would produce in free space. The difference is the metal loss, expressed in dB per octave, and it feeds directly into both the driver current rating and the metal loss correction setting on the installed driver.

Survey with the test driver, verify with a field strength meter and its signal connection cables. Doing the survey first is considerably cheaper than discovering the loss after the loop conductor is buried in screed and the driver is on the wall.

Key Features

• Quantifies structural metal loss — Measures field absorption by steel decking, reinforcement and framing before design is fixed.
• Informs driver selection — Produces the dB per octave figure that determines current rating and correction setting.
• Survey stage instrument — Used before installation rather than after, when remedial work becomes expensive.
• Pairs with field strength measurement — Works alongside a field strength meter for full IEC 60118-4 commissioning workflow.

Typical Applications

• Auditorium
• House of worship
• Conference room
• Boardroom
• Government space
• Training room
• Multi-purpose room
• Commercial meeting space

Technical Specifications

Specifications sourced from the Listen Technologies product listing. Detailed electrical data is not published for this part.

Frequently Asked Questions

What does metal loss actually mean?
Steel in a building structure absorbs the magnetic field a hearing loop produces. The loss is expressed in dB per octave and rises with frequency, which is why loop drivers provide adjustable metal loss correction.

Why survey rather than estimate?
Loss varies substantially between buildings depending on decking type, reinforcement density and framing. A loop designed on an assumed figure can fail its IEC 60118-4 measurement, and remedial work on a buried loop is expensive.

When in the project is it used?
At survey stage, before the loop design is finalised and before any conductor is installed.

Does it replace a field strength meter?
No. The test driver quantifies loss during survey; the field strength meter verifies and certifies the finished installation. Both are needed for a complete workflow.

Which buildings need a survey?
Any building with significant structural steel — composite floor decks, heavily reinforced slabs, steel frames. In practice that covers most modern commercial construction.

What warranty and support apply?
Warranty terms are set by Listen Technologies. Contact Creation Networks for current terms and hearing loop survey guidance.