Inductive loop installation

[gotty]

Sorry to raise yet another question, but I've been asked to look into including an inductive loop for the school hall as part of the sound installation.

 

The physics (and my readings) say that dynamic mics and electric guitar pickups are potentially a problem inside an inductive loop.

 

But what is the reality?

 

Since the performance area will be within the loop, and they'll be using electric guitars and dynamic mics, I'm now concerned whether I need to change the mics, limit the use of electric guitars, or suggest that the inductive loop is not practical.

 

Why is life not simple :-)

[timtheenchanteruk]

not had a problem with dynamic mics as long as they are used on a balanced system.

 

electric guitars can be a problem, depends on if they are lilkly to be inside the loop.

 

I cant stress strongly enough to get a loop specialist in to do the install, they are complex bits of kit to get right.

pasive pickups in SOME guitars is suceptible to picking up the loop, (cant remember the pickup names) active guitars and those with double coil IIRC are not affected, the double coil acting like a balanced system and rejecting the unwanted RF.

 

if at all possible the loop wants installing for the audence seating area rather than the whole lot, this seems to reduce the effects, like I say a good installer will be able to sort most if not all issues arising from the installation.

[Brian]

But what is the reality?

They don't mix. Unscreened guitar pickups and non-humbucking types make wonderful induction loop pickup coils.

[themadhippy]

The other thing that often dont play nice is old spring revereb lines.

[gotty]

Thanks for the thoughts

 

not had a problem with dynamic mics as long as they are used on a balanced system.

 

My concern is more with pickup in the mic windings (and several installation guides say "must not be used with dynamic mics" for this reason - but maybe it's not as big a problem as they suggest.

 

electric guitars can be a problem, depends on if they are lilkly to be inside the loop.

 

They will nearly always be inside the loop

 

I cant stress strongly enough to get a loop specialist in to do the install, they are complex bits of kit to get right.

 

Unfortunately the budget doesn't stretch that far, and it may be that we abandon the idea for now.

 

if at all possible the loop wants installing for the audence seating area rather than the whole lot, this seems to reduce the effects

 

I would expect it to all but eliminate the problems. Unfortunately, the nature of the venue is such that this isn't practical.

 

A concurrent post has been automatically merged from this point on.

 

But what is the reality?

They don't mix. Unscreened guitar pickups and non-humbucking types make wonderful induction loop pickup coils.

 

That's what I thought. Thanks

[ramdram]

You might want to have a look at The Disability Discrimination Act...

 

You might find these links useful:

 

http://www.jeffbyard.co.uk/induction_loops

 

http://www.guardian.co.uk/technology/2009/.../law-disability

 

http://www.hearingloop.co.uk/products/dda-legislation.html

[paulears]

If you want the areas to be served by the system to include the area within the loop then frankly, you need to look at IR not loops! It's not really much different from expecting a PA to work properly when the mics are right in front of the cabs. It's just going to feed back. It would also not really work properly anyway. If the idea is to benefit people with hearing loss, then finding a system that can cope with electric guitars and speech at the same time is going to be tricky. The system will attempt to distribute what it can hear, so the loudest source in the area will be loudest in the assist system. With two good ears, we can 'tune' out sources and focus in on wanted sound, even when weak. A mono assist system is incapable of doing this - so probably a waste of money.

 

A loop system with condenser mics could be stable, and ok for speech use - but forget it when volume creeps up!

[revbobuk]

Worth taking a look at www.connevans.com to see about personal fm solutions for hearing impaired people - many schools already use these in classrooms, and you may be able to link in to this system instead of using a loop.

[ramdram]

#7 ref IR.

 

If you were referring to the broadcast IR system, as in audio converted to IR and used to irradiate the auditorium, then ensure you are seated when googling for cost of systems...I have "used" a Sennheiser system, with two channels, for Audio Described and Sound Reinforcement...pricey.

 

These systems, at the "user interface" (sorry), have a mini loop system for use with hearing aids fitted with a telecoil. This loop is worn as a "necklace", and plugs into the mini jack socket on the main unit, (which is also worn as a "necklace"). There is also a pair of headphones supplied in the pack. The mini jack socket is the same connector for the pair of headphones.

 

I believe that some early digital aids did not have a telecoil; so despite having hearing aids the patron was obliged to wear the headphones OVER their hearing aids. (Some ladies who had glammed up for the evening were not too happy with wearing the headphones, so opted to "hang them under the chin", which seemed to work OK if their heads were wide enough.)

 

The system is not just for the hearing impaired but sight impaired. Said patrons can listen to the Audio Described broadcast, so, if they cannot see too well, if at all of course, they can enjoy the performance as tho' it was radio play...almost.

 

This way they can enjoy a social occasion with their friends and family and not feel socially isolated...ie. they get the gags as well, if sometimes a fraction late depending the skill of the audio describer.

 

Obviously we have some patrons who are both a bit hard of hearing and can't see too well either, so they can also benefit from the Audio Described. The same show relay sound signal is fed as well as the audio described feed.

 

However, they can be tricky systems to install so as to avoid obstacles blocking the IR "beams". I found that owing to the IR tx being at a certain height on the side of the pros arch and, if you were sitting in the back row of the stalls, tucked quite a bit under the balcony, the IR signal could be blocked by a large person or ladies with "big hair".

 

In this instance I had to forget hanging the rx around the neck and hold it up to get a clear line of sight to the IR tx. Finding the signal was not difficult...but holding the rx unit in the beam for the entire performance was quite tiring.

[Simon Lewis]

A few thoughts on the items discussed so far...

 

The signal can be as strong outside the loop as it is inside.

 

Dynamic mics can be susceptible, but I've not had much problems with good quality dynamics with reasonable magnetic screening.

 

Guitar pickups can indeed be a real pain, and can pick up the loop signal outside the area covered quite happily. Having said that, I have dozens of installs with loops and electric guitars that work OK.

 

The DDA talks about "reasonable adjustment". It does not mandate loops per se, (useful though they are (although Building Regs suggest an ALS in given situations)). Furthermore, there are deaf people with hearing aids that do not have a loop receiver built in, and deaf people who do not use hearing aids. A loop does not help these people (although an adaptor could be used for the former) and you could argue that not accounting for them contravenes DDA (e.g providing a BSL interpreter where needed).

Many businesses think that a loop solves all their responsibilities, and they pay to make the problem "go away". As one of the links stated, most small loop systems just don't work, and staff have no idea how to work them. In many cases, the money would have been better spent sending staff on a deaf awareness course.

 

Of equal - if not greater importance - than the transmission method is the way in which the audio signal gets into the assisted listening system. Stick a boundary mic on the wall or ceiling and the deaf person will simply not gain any benefit from it. I still see numerous loop and IR installs with inappropriate mics used to "pick up" the event. The person with normal hearing thinks it's just fine. The person with hearing loss not only loses bandwidth but also acuity - they simply cannot discriminate between wanted and unwanted sound any more. Therefore, you need to remove unwanted and uneccessary sound (including the guitars - which helps stop magnetic feedback) and specifically include speech. This is best done from a mixer with close miked sources, not from an ambient mic.

 

Loops are often preferred by hearing aid users - there's no intermediate gear to obtain/wear/get fresh batteries for/forget to return etc.

 

Having said all this, there are some smaller infra red systems available now (Sennheiser etc.) that cover around 80m^2 per unit. Although you still have the receiver management issues to deal with, they can be a useful alternative to loops - as long as the input is properly taken care of too! Hearing users will say IR sounds so much better. Many deaf users will not notice the difference.

 

Normal FM systems can tend to encroach on radio mic frequencies & bandwidth. The personal fm systems are often a 1:1 device - and may not be appropriate for a publically accessed system.

 

Bluetooth enabled aids are now available, but the vast majority of aid users have very simple (read feature reduced and costs cut to the bone) NHS jobbies that have a loop receiver.

 

Lastly, despite what many of the suppliers state, VAT relief is for personal use by specific user(s) of the aid or device. The example given is that of a nursing home: a stair lift fitted to help Mrs Jones get upstairs can be zero rated. If the home fitted a stair lift because it is a general facility or they might need it in the future, it shouldn't be zero rated. Of course, it's the seller who handles the VAT paperwork so many will simply zero rate any aid for the disabled.

 

Simon

[Stan Hope-Streeter]

... Since the performance area will be within the loop, and they'll be using electric guitars and dynamic mics, I'm now concerned whether I need to change the mics, limit the use of electric guitars, or suggest that the inductive loop is not practical.

 

Having toured into various venues with induction loops, I can assure you there WILL be problems if the performers are within the loop coverage area. You can't guarantee that every guitarist will have a super-expensive set of pickups with high immunity to external fields.

 

The loop will need to be switched off when guitar pickups are in use. This is no big deal with rock type shows, since the volume will be such that the hard of hearing will probably turn their aids off anyway.

 

Dynamic mics are less susceptible, but I'd guess that "cheap and cheerful" types might be problematic.

 

Any earth loops in the audio cabling will pick up the AFILS and this will be more troublesome than the mains hums that they normally cause.

 

If the Powers That Be insist on installing a loop, they need to be fully prepared for any additional costs of making the sound reinforcement system compatible with it.

 

Far too many loops in these places are actually a complete waste of money - the management only see them as a way of washing their hands of another piece of Political Correctness, so they don't spend the money on ensuring they work properly. A truly usable system doesn't come cheap, either in equipment or the expertise needed to design and commission it.

[Andrew C]

A truly usable system doesn't come cheap, either in equipment or the expertise needed to design and commission it.

Or keep it running, with training for FoH staff, batteries for stethoscopes (IR systems) etc

[ramdram]

Just a thought...this Bluetooth hearing aid topic might be "linked" in with the topic on the new type of FHSS radio mics discussed elsewhere in Sound...it begs yet another question of yet more rf interference in the theatre.

 

Until these topics came up you would have had NO idea of how much rf was flying around in a theatre. Amazing stuff this new technology, ** laughs out loud **.

[Simon Lewis]

Just a thought...this Bluetooth hearing aid topic might be "linked" in with the topic on the new type of FHSS radio mics discussed elsewhere in Sound...

 

Bluetooth enabled hearing aids are pretty much at the "high tech" (read expensive) end of the private market, and although no doubt they will be popular for those who can afford them (perhaps £2500 each) the majority of aid users will have less esoteric units, or standard free issue NHS ones. I'd worry more about the hordes of schoolkids with their Bluetooth enabled gadgets ;-)

 

To return to the OP's query, I would suggest he presents the pros and cons of both AFIL, IR (and possibly FM) assisted listening systems to the powers that be. Both have different advantages, and they need to make a judgement on which suits their situation best.

 

Simon