Commercial Audio 01663 Induction Loop Planning Tech Guide User Guide
- June 15, 2024
- Commercial Audio
Table of Contents
Technical Guide – Planning an Induction Loop System
User Guide
Planning the System
Induction loop system design and installation is simple, provided a few basic
facts are understood. To avoid poor performance and the need to re-position
the amplifier or loop cable at a later stage, please select the appropriate
amplifier and cable to suit the
coverage area required. However, it is important to consider the construction
of the building and the potential effect of any other equipment in the room or
in neighbouring rooms. If in doubt, please contact us for advice.
Area of Coverage
The maximum square room coverage (with ideal conditions) is usually specified
by the manufacturer. For rectangular (2:1) aspect ratio coverage this value
may be increased by around 20%. For example: an amplifier which has a square
room coverage of 200m² will cover a rectangular space with 2:1 aspect ratio of
around 240m².
Sometimes, the system may not have to cover the whole of a room. For example,
churches may only require coverage in the pews. Seek advice from the relevant
authorities before installation begins.
Loop Cable Selection
Almost any single core tri-rated cable can be used for the induction loop
provided it is of the appropriate DC resistance (ideally 0.5 to 1 Ohm).
The graph shows the recommended CSA for different lengths of loop cable.
Simply calculate the length of the loop required and choose a cable size that
falls into the non-shaded area of the graph.
For example, to cover a room 15m x 10m (150m²) the loop cable would need to be
50m long (2 sides @ 15m and 2 sides @ 10m). The recommended cable CSA for a
loop this length is between 1mm² and 2mm². Therefore, an amp which can cover
areas of at least
150m² using 1.5mm² cable would be ideal.
Loop Cable Position
The field strength in the plane of the loop (the height at which the cable is
positioned) varies greatly so it is best to install the loop above or below
the listener at floor or ceiling height (2.5m max.) – the loop field will not
be as strong but it will be more even and give better results. Listening
height (with the hearing aid user sitting or standing) is normally 0.9 to 1.8m
from the floor.
With floor loops, avoid running the loop up and over door openings as the
signal strength in the doorway will be excessively strong and may cause
discomfort to the users.
Metal Compensation
Large amounts of metal in the construction of the building can affect the
strength of the loop field. Avoid running loops along girders or under floor
mesh. If unavoidable, an amplifier with metal compensation control can help
combat the frequency response
problems associated with such installations, but overall current capability
may be reduced.
Trial Loops
Always run a trial loop and evaluate performance by listening to the signal with a hearing aid or a dedicated loop test receiver. For compliance with BS7594, we recommend you also test the system using a pink noise generator and magnetic field strength meter.
Overspill and ‘Cross-Talk’
The signal generated by the loop will radiate outside as well as inside the
loop. If there are other loop systems in close proximity, overspill such as
this may lead to ‘cross-talk’ (signals from different loops merging into one).
If this is likely to be an issue, special
designs of loop can be implemented to help reduce the overspill field – please
contact us for advice.
Asking Us For Help – Things We Need To Know
Coverage
What are the dimensions of the area to be covered (L x W in metres)?
If the room is very large, or are other loop systems fitted in adjacent rooms?
If so, a low spill phased array will be required.
Flooring Construction
The construction of the flooring can alter the performance of the loop so it’s important to find out what it’s made of. The most common flooring constructions are:
- Wooden floor boards and joists, with no metal content
- Steel re-enforced concrete slab
- Metal compartment
Audio Inputs
We need to know what audio is required to go through the system.
For example; a line level feed from an existing PA system, wireless microphone
or boundary microphone.
Building Plans
Please provide us with scaled plan drawings wherever possible, especially if
multiple loop systems are required.
Telephone: 01663 767888
www.commercialaudiosolutions.com
sales@commercialaudioslutions.com
Planning An Induction Loop Tech Guide
References
Read User Manual Online (PDF format)
Read User Manual Online (PDF format) >>