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IR Assisted Listening System

Discussion in 'Sound, Music, and Intercom' started by elite1trek, Jun 18, 2008.

  1. elite1trek

    elite1trek Active Member

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    At my theatre we have IR cameras in the house. I'm not sure what model they are. Money came through for an assisted listening system, and I don't really know what to get. I have heard that the IR systems are the best, but I am worried that the cameras will interfere with the ALS. So this is a 2 part question.

    1. Will the IR cameras interfere with the system?

    and

    2. What are the best assisted listening systems to get?

    Any insight you can provide would be great!!
     
  2. cutlunch

    cutlunch Active Member

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    As the cameras are pointing at the stage it shouldn't be to much of a problem but it also depends if you have an infrared light source used to illuminate the stage.

    I am not familar with IR assisted listening systems. These would need professional installation to work well in a theatre.

    I found this website, I don't know anything about this group apart from they help people with disabilities, but it lists the pro's and con's for each system.
    assistivetech.net AT Report - Assistive Listening Devices

    Also you'll see at the top of the page links to products and vendors.

    One of the main problems with IR is you have to give a person a receiver.

    The most common ALD system seems to be the induction loop system because a lot of hearing aids have this built in.
    So people comming to your theatre carry there own receiver for those without hearing aids that work on this (T) system you can buy head set receivers. But you would have to get a professional to install if your theatre would take it.

    Hope the website gives you some ideas.

    Just noticed at the bottom of the link the reference to disabilty law. So that might become an issue you need to look at.
    Because they are talking about 4% of your seat numbers needing receivers. Without looking at the act I don't know whether they class patrons own hearing aid with the "T" built in as excluding you from providing a receiver for that person, when using an Inductive loop system. If you go IR then you will have to buy the number of receivers equal to %4 of your seat numbers. Eg 1000 seats = 40 IR receivers needed. Whereas with Inductive that number may be lower.
     
    Last edited: Jun 18, 2008
  3. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    With any ALS system the theatre has to provide the patron with something. Most theatre box offices handle this by holding a driver's license hostage. Depending on audience demographics, a theatre may need more than 4%. The theatre needs to educate its patrons to request any special needs at time of ticket purchase.

    In 1988, my theatre used the Sennheiser ALS system with satisfactory results, except when the blue hairs would pull their white sweaters over the receiver's "eye". At that time, I believe Masque Sound was the exclusive US distributor for the system.
     
    Last edited: Jun 19, 2008
  4. Sean

    Sean Active Member

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    First of all, depending on where you are (relative level of radio traffic) an RF system may be better. They are not "line of sight", so you don't have to deal with the "sweater over the receiver" problem, and odd sightlines, etc.

    The IR emitters used for the systems are essentially a modulated IR floodlight. So, if the emitter will be in the shot of the camera (as in, you'd see the emitter's location on the TV) then you'll have a bit of flare. It looks like someone shining a flashlight at the camera. Not terrible.

    As a side note, if you have an old IR-based system, you can take the emitter and turn it around and use it as an IR flood light for your IR camera.

    --Sean
     
  5. museav

    museav CBMod CB Mods Departed Member

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    IR assistive listening systems are quite common in theatrical applications for a couple of reasons. For many years IR systems offered superior sound quality than the available induction loop or FM systems, but that is no longer as much a difference. What is a difference is that IR systems can be contained by anything opaque at IR frequencies, so IR signals tend to not extend outside the main room envelope, a factor in applications like Broadway shows, courtrooms and some government facilities where one does not want anyone outside the room to be able to easily listen to or even record the signal. IR system require a dedicated receiver that must typically be line of sight from the emitter(s). Large or oddly shaped spaces (as well as spaces like courtrooms where you may have hearing impaired listeners facing different directions) may require multiple emitters, which can increase the cost.

    Induction loop systems can offer a limited range outside the desired coverage area and some other benefits such as allowing T-coil hearing aids to be used without any special receivers or equipment, however they are also need to be correctly designed and installed as they can interfere with other devices and systems. And you cannot necessarily count on all listeners having T-coil enabled hearing aids, you still have to provide some compatible receivers for anyone who does not. Induction loop are also typically the most difficult and expensive to add to existing facilities without encountering problems.

    RF systems are probably the most common and can offer a good combination of quality, simplicity to install and cost. They do require dedicated receivers but are not limited to line of sight operation. Also, current RF ALS systems usually operate in bandwidth dedicated for this use so all the upcoming DTV and other RF spectrum changes are not really relevant.

    As far as interference, it depends. An IR system typically uses an emitter panel that is an array of individual emitters that give a specific pattern to the radiation emitted. Beyond that, it is much like an RF system but at different frequencies. You have a carrier frequency onto which the audio is modulated and a transmitter/emitter may support several channels of audio at different carrier frequencies. So whether a camera IR emitter interferes depends upon the frequencies involved and the directionality and level of the signals.

    A couple of other issues. The 4% of rated occupancy (9% in New York) for the number of receivers is based on ADA compliance but I believe that number does become a sliding scale for very large facilities, you don't need 2,000 receivers for a 50,000 seat stadium. Also, ADA compliance is often misunderstood. You are not going to get arrested for not having ALS receivers for 4% of the audience, the issue is being compliant with ADA should there ever be a problem or complaint. If someone files a complaint you may be asked to show compliance, if you are found to not be compliant then you typically will be given an opportunity to show a reasonable attempt to comply. Being compliant from day one is a good idea but many facilities are not technically in compliance with the ADA requirements on ALS and never receive a complaint, in fact depending upon the audience it is fairly common for a facility to start with fewer than the 4% requirement for receivers and then increase the number as they find is required to serve their audience.
     
  6. Van

    Van CBMod CB Mods Premium Member

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    Check out Listen Technologies they are from Salt Lake they are super nice, their prices are fantastic, and they are 100% forward compatible withe all the new FCC bandwidths set aside for the purpose of complying with the ADA. I Highly VErily, and wholeheartedly discourage you from using an IR Assisted listening system. Even the absolute best ones are fraught with problems. I hate and detest them.
     
  7. TimmyP1955

    TimmyP1955 Active Member

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  8. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    So your next hurdle is how/what to feed it. I suggest a shotgun mic from an FOH lighting position, or possibly just in front of the sound booth.
     
  9. museav

    museav CBMod CB Mods Departed Member

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    If it is practical, I prefer to run the ambient mic into the console and use an aux send for the ALS system. Not only does that let you create a mix just for ALS, for example maybe adding in some character mics directly for intelligibility, but that ambient mic can also be handy to have included in recording, BOH and other mixes.
     

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