Audio

Aid Memoire! A Follow up to ‘Loop Gain’

It would seem that my September and October 2015 discussions have sparked more interest than almost any other I have written over the past eight years. You’ll find two of the emails printed below. I have added some additional information to them to conclude the topic…at least for now!

Thank you for the excellent articles in your September and October issues on audio frequency induction loops systems (AFILS). Dr. Mapp is obviously an AV engineer who gets it: Loops and telecoils (T-Coil) are the most user friendly ALS because they free the user from borrowing equipment and also from realizing too late that a receiver/headset/neck loop is needed and to borrow one. Accessing the ALS by simply touching a button on a hearing aid or cochlear implant makes loops the preferred system for almost any hard-of-hearing person in any large public venue.

It’s unfortunate that, in my experience, too many AV engineers look at assistive listening systems from the perspective of easy installation rather than from the user’s perspective. In order to meet the requirements of the ADA [Americans With Disabilities Act], assistive listening systems must consist of more than just loudspeakers, so they sell and install FM and IR systems that integrate receivers and headsets (or since 2012, some neck loops) that studies have shown are simply not used by those most in need of clear, clean sound (the hard of hearing).

They apparently don’t understand (or don’t care) that hard-of-hearing visitors to a venue may not realize until too late that they are going to need a receiver and headset or neck loop. They don’t understand that many have hygienic concerns in regard to the loaner headsets, object to calling attention to their disability by donning a headset, or find it a real inconvenience to have to seek out a source to borrow and then return a receiver.

Small, independent AFILS installers are cropping up all over the US and, with the advent of national looping campaigns by the Hearing Loss Association of America, SERTOMA and others, plus a growing number of community efforts by concerned citizens who live with a hearing loss, AV firms are, in my opinion, losing business to start-up looping installation companies for no good reason other than a lack of awareness of the real advantages of AFILS and the knowledge required to properly install the systems.

In my own experience, I usually refer inquiries regarding the sale and installation of a loop system to those I know who specialize in them and warn the applicants that, if they wish to go to a large AV firm, to insist that they want a loop system because, too often, people have come back to me with a report that the AV firm attempted to direct them to an FM or IR system instead of a loop.

I suggest to any firms not already familiar with AFILS and trained to install these systems, that they seek out one of the many manufacturers/distributors of the equipment and sign up someone on their staff for the training offered in this technology.
—Stephen O. Frazier, Hearing Loss Support Specialist

Many thanks, Stephen, for your input and reasoned discussion. It is true that infrared (IR) or wireless systems are often easier to install than an effective loop (it is often not just a matter of running a cable around the perimeter of the room). However, on occasion, a combination of technologies may be required. The hearing aid is designed to optimize speech clarity and intelligibility for a hard-of-hearing user in ways that other systems cannot replicate. However, the installation of the loop cable (or antenna, as it is officially known) can be difficult or even impractical in some large venues. Here, a neck loop, used in connection with an IR system for example, can provide an excellent solution.

I do not think it unreasonable for hard-of-hearing attendees to have their own neck loop and bring it along to a venue, particularly if that venue is one that they regularly attend or suspect will have an assistive listening system. For example, every London West End theater has an infrared system (as do most provincial theaters in the UK). So, if you are going to regularly attend one of these venues, it would be worth having your own neck-loop and receiver. This does, of course, assume that the system is actually on and the signal being transmitted is adequate. This can be readily checked out by theater staff/sound technician, etc., because the venue owner/operator has a greater responsibility than just having an assistive listening system: It has to be working and effective.

I was intrigued to learn recently of a court case in the UK where a hearing-aid user sued the venue for not providing an effective assistive listening system. Now, this may be of no surprise in the litigious US, but here in the UK, this is almost unheard of and, indeed, the case has set a legal precedent. To summarize the saga, it would appear that the hearing aid user was going to attend a meeting (ironically, concerning people with hearing and vision disabilities) at a particular venue and inquired beforehand if they had a deaf aid/induction loop (AFILS) system.

He was told that they did and was directed to sit in a particular seat location. For three hours, this individual sat where directed and heard nothing through his hearing aid when switched to T-Coil. (How many people realize that the effective range of a normal hearing aid is only about six feet or a couple of meters…something that few device manufacturers will tell you!)

When he complained that there was no hearing loop signal, he was told that the hearing loop provision was adequate and regularly tested. Not being satisfied with either the answer or the way he was dealt with, the hearing aid user sued the venue owners under UK discrimination law. For some reason, they decided to contest the case. Expert opinion was sought and it was shown that the portable loop system provided was inadequate for the purpose intended and that, indeed, the hearing aid user in question would not hear a useful/intelligible signal via the system.

The venue owners lost the case. Ignorance, it would appear, is not a viable defense! It is too soon to see what impact this case will have, but it has put down a very firm marker. Now, if the same logic were to be applied to PA systems in general, then we could be in for some interesting times. So it is clear that just providing an assistive listening system is not enough: It actually has to be effective! This brings me to my second correspondent:

Thank you for your articles. Your column is one of two each issue that are on my “must read” list.

My interest was definitely peaked by your mention of induction loop systems. And I would welcome an article highlighting the pros and cons of the various solutions, as they might be used in a house of worship (HOW) in the US.

Frankly, in my limited experience, no ALS solution has a highly desirable outcome. And induction loops seem to me to be an ineffective solution where I live.

Here’s my saga (the long version):

Several years ago, an acquaintance returned from a trip to Europe and promptly insisted that we install an induction loop type ALS in our church, based on his positive experience in a cathedral he toured. Having no knowledge of ALS systems, I began researching and contemplating a solution for our HOW, where I am the “tech guru.”

My first inclination was to throw a bunch of 14-2 Romex above the ceiling, connect it to a power amp that can tolerate a 2 ohm load and, as a frame of reference, see what happens. However, it occurred to me that I could get feedback from our Helpinstill piano mic (a magnetic pickup). After pondering whether the loop would, indeed, dump much magnetic energy into the piano mic, I concluded that it wouldn’t reach to the piano, and also would not reach the pews(!) because of the distance involved and practical limitations concerning the diameter of the loop in our facility.

So I drew up a floor loop plan that would not encroach on the piano, but still cover about 70% of the seating area. But then the shunting effect of the rebar in the concrete floor concerned me. After puzzling over that situation, I concluded it was nothing that a big enough power amp couldn’t overcome.

I then went to the church board with the possibility of installing an ALS inductive loop in the floor. However, because a new sanctuary was on the horizon a few years down the road, and the cost of installing wire under a carpet floor was substantial, they nixed the plan.

A couple years later, a church member suggested that the board consider purchasing a wireless system, so his elderly father could hear better. The board was favorable to that solution. I noted that we could implement a comparable (temporary) system at no cost. It turns out that our musicians were using an Aviom-based IEM system, and had implemented two channels of wireless IEM using Sennheiser EW IEM G3 units. Because they only were using one of the two channels, I absconded the second transmitter for ALS.

Our Soundcraft GB4-32 mixing console has an output with a limiter, so I used it to feed our “homebrew” ALS transmitter. I also added the center channel (which was previously unused) output to the ALS input, and mapped our “announcements” mic and pastor’s Countryman mic to the center channel (in addition to L+R). I then turned up the center channel master so speech would come through the ALS at nearly the same volume as the music portion of our worship service. I also added a simple R/C network to the connection between the mixer and the ALS transmitter so we get about 6dB of boost at the consonant frequencies. Thus, we have an ALS system with limited dynamics and some EQ (to somewhat compensate for the fact that people are using conventional earbuds rather than their hearing aids).

Finally, I ordered one necklace loop and we made a sign advertising the availability of ALS devices.

To my surprise, no one has used the necklace loop. It turns out that, in practice, it simply does not work! Few people in our church know what a T-Coil is, or how to enable it on their hearing aid.

In the past (and when the guy mentioned earlier went to Europe), hearing aids had a “T” switch on them. But no more. Furthermore, when I visited our local hearing aid store, they told me they do not normally enable the T-Coil feature because it is not needed and only confuses the user.

I had a friend ask that his T-Coil feature be enabled, but it still does not work. He said they explained to him that it did not have an On/Off setting, and was “automatic.” I wonder how the automatic feature works: Does it detect the magnet in the earpiece? If so, then a loop necklace is not going to work because it has no magnet and is not even within sufficient proximity to the hearing aid for that to work.

I am aware that many hearing aids have Bluetooth [BT] capability. However, I am not aware of any BT profile that accommodates any sort of broadcast mode. Thus, any BT solution has to be implemented on a one-to-one basis, and thus is not feasible in a public venue. So, in summary, it seems to me that BT and loop solutions are not practical. And I doubt IR would be obstruction-free in a large room.

Obviously, my experience and expertise in ALS is quite minimal! Thus, I would welcome an article highlighting the comparisons of various ALS solutions, and specifically addressing the various peculiarities and practical issues that arise in real-world HOW situations in the US.
—Tim

Tim highlights some interesting and highly relevant points and I have to admire his resourcefulness. I am a little surprised that the neck loop did not work. It certainly should, and should be designed to produce a local magnetic field of the strength required by a hearing aid and in compliance with IEC 60118-4, which defines the magnetic field strength requirements for induction loop systems for hearing aid purposes. A long-term average level of 100mA/m with a 12dB headroom capability (i.e., allowing max RMS “peaks” of 400mA/m). The frequency response and other parameters are also defined in the standard.

If the RF receiver and neck loop were working correctly, a hearing aid fitted with a T-Coil should certainly enable speech of adequate level to be heard via the hearing aid. However, this assumes a vital point: that the T-Coil capability has been activated. Worryingly, as you indicated, many audiologists and hearing aid dispensers do not activate the capability; primarily, it would appear through ignorance and not understanding (a) the limitations of the hearing aid or (b) the benefits that a good loop system can provide. It begs the question, “Are hearing aid users and dispensers in the US less capable of dealing with the technology than their Northern European counterparts?”, as the latter seem to cope adequately well and users derive considerable benefit from the facility!

I suspect that, to deal with the topic in more detail is beyond the intent and scope of this column, but if there is sufficient interest, I could certainly write a separate feature. A few further points to close with:

  • Loop systems can be designed to specifically not cover a given area so guitar pickups, magnetic pickups and organs/other magnetic field-sensitive musical instruments and equipment are not affected.
  • The electromagnetic field strength of a loop is highly predictable, and sophisticated computer programs exist that will compute and display the expected magnetic field and its strength.
  • Digital hearing aids without a remote control usually have a button that steps through the programs that have been set up by the dispenser. Remote controls usually have a similar stepping system. It is to be hoped that the programs include a “T” program and preferably an “MT” program (microphone with T-Coil signal) as well, but some dispensers may not provide either unless asked (demanded, it would seem in many cases!).

There are fewer hearing aids these days that don’t have T-Coils, but the smallest TIC ones (Totally In-Canal) may have a smaller horizontal coil, which is not as effective (or, as one UK expert told me “a bit better than nothing”).

Some US hearing aids have an internal magnetic T-switch that operates if a phone (or any permanent magnet!) is held to the ear. This doesn’t work with loops, of course, although I gather that there is at least one hearing aid that does have a loop detector.

  • Although deaf aid loop systems (also known as AFILS) can work extremely well, they are not always the optimal/most cost effective solution in some venues/situations; in those cases, other technologies or combination of technologies might have to be used.
  • There is more to installing a viable loop system (AFILS) than many people might imagine. Many factors have to be taken into account in determining the best loop layout and format to use. Long gone are the days of just connecting a wire running around a room to an amplifier that can tolerate a low impedance inductive load. Potential installers have to be chosen with care.
  • At the present time there is no universal Bluetooth protocol for hearing aids, so they are only compatible with dedicated transmitting equipment from the same manufacturer. This is hardly viable for a “public” building.
  • All that being said, it shouldn’t be forgotten that hearing aids are designed primarily to optimize the reception and intelligibility of speech, but some of the associated DSP algorithms and processes can be detrimental when listening to music. However, that’s a whole different can of worms.

In the meantime, may I wish you a happy, prosperous and intelligible New Year.

Previous ArticleNext Article

Send this to friend