Series on FM: Soliciting User Experiences&c.

Update #1 January 27, 2011: Please scroll halfway down to red portion of the text

The project of rating two new digital FM systems, the Bellman & Symfon Audio Domino (PDF w/specs) ($495 street)  and the Etymotic Research Companion (specshow it works) system ($699 street w/three transmitters and ER-6i isolator earphones) is turning out to be a three-part series of articles, taking much more time than I expected… And I am soliciting comments on any FM system about your user, parent, teacher or hearing healthcare professional experiences — Good .AND. Bad. Please post your experiences in either the Comment section below, or email them to me at Dan@Snip.Net

The first of the three will be how and why FM — When it’s done properly — is a tremendous help to the hearing impaired and others, from infants & toddlers receiving auditory therapy, to children (including those with cognitive impairments), to high school & college students in large classrooms & lectures, to adults on the job, and in noisy social situations, to the elderly watching TV.

Most of the first article in this series will center upon the discussion on these 4 pages in Jamie Berke’s About.Com Deafness Forum.  [And Yes, the story about the beer is true!]

The second article in the series will deal with the situation when FM is .NOT. done properly, and interference or other issues result. Phonak’s FM system appears to be a serial offender, but there are other culprits. This article will go into the techno-details on things like multipath distortion vs dropouts, transmitter power, and other things a computer geek or Ham Radio operator would understand… So the challenge is to make it readable for the average parent.

The third article in the series will be test results from these three systems:

§ The Bellman & Symfon Audio Domino (PDF w/specs) ($495 as tested with earphones) is a flexible single transmitter system, with excellent audio quality, decent range, and highly directional microphones on both the transmitter & receiver;

§ The Etymotic Research Companion (specshow it works) system ($699 as tested with three transmitters and ER-6i isolator earphones) ships with either one or three transmitters, and is the only system (besides the Phonak DynaMic extension to the troublesome Inspiro) that provides many-to-one capability;

§ The Comfort Audio Contego ($795 as tested w/neckloop) is a single encrypted transmitter system; and was screened by the author at the HLAA Convention in Milwaukee.

Update #1: Due to time constraints I have not been able to fully update this blog entry; however I posted this reply on Dr. A.U. Bankaitis’ blog:

Although they have differences, the Bellman Audio Domino Classic costs $200 less, and performs as well as the Comfort Contego. While the Contego has a zoom mic, the Audio Domino Classic has a tone control on the receiver, and also when stereo is input into the transmitter jack, the system switches to digital stereo (more on this in a moment).

Previously, A.U. raised a point about the 40ms latency of the Audio Domino vs 10ms delay in the Contego (vs. no latency with analog!) and how it can interfere with lipreading cues. [Note:In googling Comfort Contego specifications there is no mention of latency.] From personal experience, I haven’t noticed any latency issues; but more importantly, if either system is used with a TV, it is important to note that with the shift from NTSC to HDTV the lead/lag for the separate AC3 and MPEG audio streams can be up to 150mSec (and in practice is often much higher), so the (supposed) 30ms delta between the two doesn’t seem to be a factor.

Now, let’s say your patient wants a zoom mic on the transmitter & receiver: With the Contego, the user has to walk over and manually switch the transmitter. But, remember when I said above that the Bellman Audio Domino Classic transmits in digital stereo? Well, so does the Audio Domino Pro… But also, the Pro version does something Really Clever: The audio from the omni mic rides on the left channel simultaneously with the audio from the zoom mic! This way, the user need only push the button on the receiver to “zoom” the transmitter, saving endless user fiddling.

My friend Sarah, who blogs on her Speak Up Librarian website received upon my recommendation the Audio Domino Pro from her employer to use at work. She wrote two extensive first-person reviews here and here that are worth reading.

Finally, I welcome everyone’s own observations of FM ALD’s, whether good or bad; clinician or user, on The Hearing Blog’s article covering all things FM.

Update #1: January 27, 2011 @3:45PM EST

← Failing Ugly: Advanced Bionics cochlear implant circuit goes haywire Hearing Loss Ass'n of America Convention 2010 summary (updated) →

About the author

Dan Schwartz

Electrical Engineer, via Georgia Tech


  1. PinkLAM
    July 14, 2010 at 12:02 am

    I’m not sure how much I’ve told you about the FM brands I’ve specifically used. I’ve found that out of all Phonak’s FM systems, the Smartlink works best for me. I tried the (new at the time) Inspiro and had awful static and interference. With the Smartlink it was greatly reduced, but is still touch and go. Before I had my implants I used the Lexis (not sure who makes it, but I think Oticon has an FM that looks exactly the same). [Editor’s note: Oticon indeed makes the Lexis.] It’s silver and sort of oval shaped) and had good results with that. I was not wild about Phonak’s FM that I think was called the Campus SX — the unit itself always seemed to be breaking. I also used the Oticon Amigo for a short time, but found it did not bring in as much sound as the others. I think it may have been that the ratio and/or volume was set differently.

    I will be interested in hearing your reviews of other systems!

    • Supervisor
      July 18, 2010 at 8:25 am

      PinkLAM: Thank you for the update! It was you who brought this issue to my attention with details I had never seen before. I had seen scattered reports on the About.Com thread on FM, but many of these reports were from years ago, and traceable to the use of the induction neckloop — T-coil method of coupling.

  2. Miranda Smith
    August 5, 2010 at 11:22 pm

    I’ve used two different FM systems and I hated them both. They both broke in less than a year. My first one was the Oticon Lexis. I really liked how it work, I didn’t get much interference and it had a long range so if my teacher went out in the hallway I could still hear them (and I overheard alot more than I wanted to with that thing.)I also liked how simple the controls were and was easy to take on and off. However after about 6 months the unit stopped taking a charge. I changed batteries and it still didn’t fix it. I was only able to get an hour use of it at a time before it would die. It would have been a decent system if it worked for longer than it did. After that died I got the Phonak Campus SX. I didn’t like this one at all from the very beginning. In order for the wearer to use it, they would have to uncoil the antenna, clip one part to their belt and the mic to their shirt. This would be fine for an elementary school student that has the same teacher the whole day but not for a college student who changes classes every hour. Also, if the wearer accidentily bumped it and hit a button it would change the channel rendering me unable to hear what was going on. The Campus SX also had a more limited span than the Lexis, if I sat towards the back of the classroom it would start cutting out. Those are the only two I’ve had and I’m getting fitted for new hearing aids the 18th of August, I didn’t even bother asking if they were FM compatible because I kind of gave up on them because of those two bad devices.

    • Supervisor
      August 6, 2010 at 10:32 am

      Hi Miranda!
      Thank you for your detailed reply. I’d like to ask you a few questions and make a couple comments. Please reply here; but any details you’re not comfortable with, you can email me at Dan@Snip.Net

      1) What are you using for receiver(s):

      * Are they microLink (thumbnail) size on each hearing aid?
      * Is it a single receiver plugged in via Direct Audio Input (DAI) wire?
      * Is it a single receiver coupled in via neckloop?

      2) Do you have any lab classes in college with partners?

      3) How severe is your hearing loss?

      4A) Have you chosen your new hearing aids yet?

      4B) Will these hearing aids have Bluetooth capability via streamer (Oticon Streamer or Phonak iCom)?

      5) Does your college supply the FM; or does Vocational Rehabilitation?

      OK, now let’s do a cursory failure analysis:
      Looking up the Oticon Lexis, it’s actually a system, not an individual transmitter. That being said, you probably had the integrated unit worn by the teacher as a pendant.
      The battery issue is something generic, though: For any rechargeable battery chemistry (Li-ION, NiMH, even lead-acid) you want to leave them on the charger topped off, unless actually using it untethered (applies to laptops, cell phones & such, too); as leaving it in a fully discharged state is deadly.
      However, since you replaced the battery and still only got an hour, that means either the replacement cell is bad (can happen), or more likely there is a short in the circuit, which would be repaired by the factory under warranty, replaced by your school or DVR, etc…
      The fact that it had little interference and worked well should point you back to using it again;

      Now, your analysis of the Phonak Campus SX is interesting: There is a keypad lock you can use; but I understand hustling from class to class and wiring up the prof each time, and the stares it gets from students.

      However, Phonak has a nasty habit of limiting transmitter power to 10mW, even though 100mW is allowed in US and Canada, in order to “harmonize” their worldwide distribution for their “convenience” — North American users be damned. [And, I took their VP of regulatory affairs over in Switzerland to the woodshed over this very issue, as more transmitter power would fix interference problems.]

      My suggestions:

      1) Don’t give up just yet on FM — Life is too easy in college do not have it, especially when the lecture hall is large &/or has poor acoustics; or the prof mumbles into the blackboard, has a thick accent, or both!

      2) Find out which HA’s are being recommended to you, and write back, along with what your present hearing aids and receiver(s) are. Also, if you can, take a snapshot of your HA’s (w/earmolds) so I can analyze them;

      3) Also, if you have an audiogram, scan it in & email it to me, and I can make alternate suggestions.

      4) Take a few minutes to read this important thread on FM on the Deafness Forum; and see if any of the things described in there match up with your experiences; and post a reply.

      Dan Schwartz

      PS: The story about the beer in the Georgia Tech lecture halls is True!

  3. Miranda Smith
    August 6, 2010 at 4:20 pm

    I used microlink receivers for the campus sx and I think the lexus had its own kind of receivers but both were boots that connected to my hearing aids. I only had one lab class but I have a notetaker for all of my classes. They give me carbon copy of their notes after class just in case I didn’t get all of the lecture. My hearing loss is a little odd to say the very least…I used to have a severe/profound loss in both ears but I now have a mild/moderate loss in both ears. I was going through the candidacy process for the CI when they noticed that my ABR only showed a mild/moderate loss and diagnosed me with a central hearing loss. Through more testing and other process they found the cause of that loss (if you need more details I will elaborate in private.) but I still have a mild/moderate sensory-neural loss. My previous hearing aids were Oticon Sumo and I was using a skeleton type mold. Here is a picture of those: [Editor’s note: Image inserted]
    Miranda Smith's Oticon Sumo hearing aids

    I will be getting fitted for the Oticon Epoq, they have already been picked out. I know it is compatible with the Streamer but not sure if it comes with it or you have to get it separately. [Editor’s note: The Streamer is a separate option.] I guess I will find out in 2 weeks. I don’t have a recent audiogram yet, but I can ask for one when I get it and send it to you. Vocational Rehab has payed for both hearing aids and FM. My insurance only covers a minuscule amount of my hearing aids and OVR picks up the rest. I still have both how ever I have no idea where my boots are for the lexus, I moved and things have gotten separated so I would have to go looking for them. I’m going to donate my campus sx though because I think someone will find better use for it than I did.

    [Editor’s note: Image embedded and three external links to Oticon’s products added for clarity on August 12th, 2010.]~

  4. Hearing Aids
    January 13, 2011 at 3:05 am

    Superb blog post, I have book marked this internet site so ideally I’ll see much more on this subject in the foreseeable future!

Leave A Reply

Time limit is exhausted. Please reload CAPTCHA.

%d bloggers like this: