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 FAQ's about hearing aid loops
Where can I find out about the Disability
Discrimination Act (DDA)?
- Visit the Government
website
- Contact your local council's
Access Officer
- Ask us
for help - we have a leaflet available too
-
Can I use electric guitars with the loop
system?
- Generally, electric guitars cannot be used within a loop
system.
- The "pick-up" coils on electric guitars will pick up the
electromagnetic field from the loop system in tha same way that the "pick-up"
(telecoil) in a hearing aid. If the guitar is used with its own "combo"
amplifier, the signal from the loop will be picked up by the guitar, and heard
through the guitar amplifier's speakers. Worse still, if the guitar sound is
fed to the loop system, feedback will occur. Acoustic guitars with "crystal"
(eg Barcus Berry) or Electret (eg C-ducer) pickups are not affected.
-
What type of microphones can be used with
loop systems?
- Ideally, phantom powered electret condenser microphones.
Dynamic microphones may cause problems because the coil in the microphone will
pick up the magnetic field from the loop, possibly causing feedback
-
I need to fit a loop system in a meeting
room. There is no need for a PA system but do I need a microphone?
- Yes, loop systems need microphones, but remember that
several microphones may be needed so that one is always close to the talker
!
-
How do I stop my electronic keyboard from
picking up the loop signal?
- Most modern electronic keyboards are not affected by loop
systems, however if "hum loop" if formed by the cables linking the keyboard to
an amplifier, the system may pick up the loop signal. Use an active Direct
Injection Box, or a good quality passive DI box with a screened transformer.
NEVER remove electrical earths from mains powered equipment. They are there for
your safety. We also recommend a RCD "powerbreaker" type device should be
fitted to ensure the safety of performers.
- How do I connect several
microphones to the loop amplifier?
- Microphones need to be close to the talker, so that they
pick up mostly the talker, with the minimum other noise or reverberation. If
several microphones are "on" then all microphones except the one nearest to the
talker pick up background noises or reverberation from the room. If more than 3
microphones are used, an automatic microphone mixer is recommended. This
"reduces" the sound from microphones that are not "in use" ensuring the best
sound is fed to the loop system
-
Can I use a PA or HiFi amplifier to drive
the loop cable?
- No. A specially designed loop amplifier is required.
Conventional amplifiers are designed to drive loudspeakers, and are called
"voltage amplifiers."
Loop amplifiers are "current amplifiers", designed to
give the appropriate current in the loop, even though the impedance of
the loop rises with frequency.
-
How many "turns" or cores of wire should I
use for the loop?
- We recommend single turn loops, as there are problems
associated with multi-turn loop cables due to the high voltages required to
produce adequate current at higher frequencies. This is due to the rise in
electrical impedance of the loop "coil" which rises with frequency, compounded
with the rise in impedance proportional to the square of the number of
"turns", (eg. A 2 turn loop will need 4 times the voltage to drive it, while
only gaining a factor of 2 in the effective loop current contributing to the
magnetic field strength.)
- How can I have more than one loop system in
the same area?
- I
already have microphones and a sound system, what do I need to
provide a hearing aid loop?
- If you have an existing sound
reinforcement system, to add a hearing aid loop you will
need to add a loop amplifier and install a loop cable. The
loop amplifier typically connects to a line (aux or,
record) output of the mixer or integrated mixer/amplifier,
so whatever is amplified by the sound system, is relayed
into the loop. If there are times when all the microphones
are switched OFF, it is advisable to install a dedicated,
omni-directional microphone connected to the loop
amplifier to provide ambient sound to the loop.
List
Of Brands for Audio Frequency Induction Loops
AVX
Univox
You can BUY LOOP AMPLIFIERS and ASSISTIVE
LISTENING DEVICES at our ONLINE
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