Posted on Friday, 12th September 2014 by Cynthia Compton-ConleyPrint This Post
Hearing aid and implant wearers know only too well that their devices perform best when in close and quiet listening situations. However, listening may not be so easy when attempting to understand dialogue on the TV, over the phone, or when listening in noisy situations such as in the car, restaurants, or movie theaters and lecture halls. Although directional microphones are being used in hearing instruments to improve understanding in noise, the degree of improvement depends upon several factors including distance (how far you are from the sound source) and how much noise and/or reverberation is in the room, etc. To ensure that your hearing instruments meet your listening needs in all situations, it is important that they be equipped with wireless receivers. Currently there is no one “universal” wireless receiver. For now, wireless receivers can be of several types:
- NFMI (Near Field Magnetic Induction)
- 2.4 GHz
- 900 MHz
A telecoil is a small circuit consisting of copper wire wrapped around a small permeable metal core. It is designed to function like an antenna for the pickup of electromagnetic signals sent from inductive devices such as room loops, neckloops, or hearing aid compatible phones. When the hearing instrument is set to “T” (telecoil mode), its microphone is turned off and the hearing aid is ready to pick up electromagnetic signals from the inductive devices mentioned above. Your hearing instrument also can be equipped with the M + T option, meaning the microphone (M) and the telecoil (T) can be activated simultaneously, thus allowing you to listen through a room loop or other device and continue to monitor the outside word (your own voice, a companion’s voice, etc) By using a telecoil with an assistive listening device such as a room loop, or a neckloop along with an FM or infrared receiver, you can hear better across distances than you can with your hearing aids alone.
Using a telecoil with a hearing aid compatible phone can make it easier to understand speech in noise and prevent feedback, that annoying “eeeee” sound that can occur when you hold a phone up to your hearing aid.
Although telecoils have been in use in the United States since 1947, they have recently enjoyed a renaissance due to the increasing popularity of loop systems. Many public places now have installed room loops as a way of providing hearing access to people with hearing loss. To read more about loops and the loop movement, go to this link: http://www.hearingloop.org/.
Telecoils are inexpensive and can be installed inside of all brands of hearing instruments as long as they are large enough to accommodate the circuit. In my opinion, to achieve the most listening flexibility most hearing aid users (and all implant users) should use hearing instruments equipped with telecoils. While you may decide to use a different form of wireless technology to connect to the phone and to TV or your spouse, for now, telecoils are essential if you want to connect to wireless assistive listening devices (ALDs) used in public places such as lecture halls, convert halls and movie theaters. To read about these devices, go to this link: http://soundstrategy.com/content/technology-enhancement-media#alds.
NFMI, 2.4 GHz, and 900 MHz
NFMI, 2.4 GHz and 900 MHz are newer wireless receivers that are now installed in certain hearing aids and/or implants. They are used in conjunction with wireless transmitters and special devices called streamers. Streamer is just another name for what is really a transceiver. A transceiver both receivers and transmit a signal. It serves as a gateway between a wireless transmitter and the receiver inside of the hearing instrument. It’s job is to change one form of energy into another.
NFMI systems consist of a Bluetooth® transmitter, a Bluetooth® and NFMI transceiver (streamer), and a NFMI receiver built into the hearing instrument. The Bluetooth® transmitter may be located inside of a Bluetooth®-enabled phone or it may be plugged into the audio board of a TV or other device. It also may be in the form of a battery-powered microphone clipped to someone’s lapel. The Bluetooth® signal from the transmitter is sent to the streamer that you wear around your neck, hold in your hand, place in your pocket, or place upon a table. The streamer changes the Bluetooth® signal into a NFMI signal and re-broadcasts to your hearing instruments. The transmission/reception sequence looks like this:
Bluetooth® Transmitter -> Bluetooth®/NFMI Streamer -> Your NFMI-equipped Hearing Instruments
NFMI systems require you to always have your streamer with you if you want to be connected to a Bluetooth® signal.
2.4 GHz and 900 MHz Systems
2.4 GHz and 900 MHz systems required that you use a streamer when using a Bluetooth® phone. However, they do not require the streamer when using their battery-powered microphones or plug-in 2.4 transmitters. For example, if you want to wirelessly listen to TV (or another sound source) at home, you simply plug a 2.4 Hz or 900 MHz transmitter into the audio panel of your TV. The transmitter then sends the TV signal across the room, directly to your 2.4 GHz or 900 MHz wireless hearing aids. In the same way, if your spouse uses a battery-powered 2.4 HZ or 900 MHz lapel microphone, his or her voice is sent directly to your hearing aids. However, if you want to use a Bluetooth®-enabled phone, then you must use a streamer that picks up the Bluetooth® signal and changes it to either 2.4 Hz or 900 MHz and then re-broadcasts that signal to your hearing instruments. Note: ReSound’s new 2.4 GHz LiNX™ hearing aids allow you to broadcast phone calls, face-time calls and media from an iPhone5®, iPad® or iPod touch® directly to the hearing aids. This system uses a type of 2.4 GHz technology with that is also called Bluetooth® Smart. It also works with ReSound’s TV transmitter and wireless microphone transmitters.
For (1) TV (and other devices), (2) Bluetooth®-enabled phones, the transmission/reception sequences look like this:
- 2.4 GHz/ 900 MHz TV Transmitter -> 2.4GHz/ 900 MHz-equipped hearing instruments
- Bluetooth® phone -> Bluetooth®/2.4Hz/900 MHz streamer -> 2.4GHz/ 900 MHz-equipped hearing instruments
With the new iPhone 2.4 Hz LiNX system, the transmission/reception sequence looks like this:
iPhone 5 -> ReSound LiNX hearing aids
Meeting “Near-field” and “Far-field” Listening Needs
The environment in which we listen is called the sound field. It consists of close and far listening situations. When listening at close distances, such as when listening on the phone, watching TV, or conversing with one another, you are fairly close. As such, you are considered to be listening within the near-field. This is where the newer wireless systems like NFMI, 2.4 GHz and 900 MHz shine. As long as you have your transmitter and/or streamer with you, you can wirelessly pick up the signal of interest to you, even in challenging listening situations.
IMPORTANT POINT! When listening in large venues such as classrooms, lecture halls, concert halls and movie theaters, you are engaging in far-field listening. In this situation, wireless systems will NOT solve your listening issues unless you have a telecoil circuit – either inside of your hearing instruments or inside of your wireless streamer.
The newer wireless systems, especially the 2.4 GHz, are touted as being the most advanced due to their technology and the fact that you can go without a streamer when using the 2.4 GHz transmitters with TV (and other sound sources) and the portable microphone. However, it is not being used to broadcast in large venues.
The only wireless transmission systems now being used in public areas are loop, FM and infrared transmission. These systems are mandated by the Americans With Disabilities Act. Loop systems require that you have a telecoil. This telecoil can be inside of your hearing instruments (as discussed above) or can be inside of a wireless streamer that you must purchase and bring with you to the venue.
With loop systems, the electromagnetic energy sent from the loop installed in the room must be picked up by a telecoil. If inside of the hearing aid, then all you do is walk into the looped room, set your hearing instruments to telecoil mode and, voila!, you begin to hear. If you do not have telecoils but you own a streamer that contains a telecoil (not all streamers do), then the loop sends to the telecoil inside of the streamer and the streamer then re-broadcasts the signal to your hearing aids via NFMI, 2.4 GHz or 900 MHz. The transmission/reception sequences for using a room loop (1) with telecoils inside of your hearing instruments versus (2) inside of your streamer look like this:
- Loop transmitter -> Telecoils inside hearing instruments
- Loop Transmitter -> Telecoil-equipped streamer you bring with you -> wireless hearing aids
If the room is equipped with an FM or infrared system, then you must wear an FM or infrared receiver that you borrow from the venue. If your hearing loss is mild, you can remove your hearing aids and use earphones with the FM or infrared receiver. If not, then you must borrow a neckloop from the venue and plug it into the receiver so that you can use it with your telecoils. This is necessary because the FM or infrared signal must be changed to an electromagnetic signal in order to be used by the telecoil. If you do not have telecoils inside of your hearing instruments, but you own a telecoil-equipped streamer, then you can position that inside of the FM/infrared receiver’s neckloop. This can be tricky (clunky), which is why it may make sense to be sure that your hearing instruments are equipped with telecoils.
The transmission/reception sequences for using an FM or infrared receiver (1) with telecoils inside of your hearing instruments versus (2) inside of your streamer look like this:
- FM/infrared transmitter -> FM/infrared Receiver equipped with neckloop -> Telecoils inside hearing instruments
- FM/infrared transmitter -> Telecoil-equipped streamer placed within neckloop of borrowed FM/Infrared Receiver -> Wireless hearing aids
Again, not all streamers have telecoils. So, before you decided on a wireless system, assess your near-field and far-field listening needs at home, at work and at play so that you can decide which way you want to go.
My advice right now would be to follow Dennis Damp’s lead and consider a 2.4 GHz system for your near-field needs and be sure that your hearing aids also contain telecoils that are positioned vertically and programmed properly so that when you switch from microphone to telecoil mode the loudness and sound quality will be the same. You might also want to make sure that your hearing health care professional provides you with an M + T option. This will enable you to hear the target signal through the wireless system as well as the outside world. For example, you may want to monitor your own voice or hear comments from your companion. If, however, the room acoustics are bad and you just want to hear what is coming through the wireless system, then you can go to the “T-only (telecoil only)” mode. This is similar to what normal hearing folks to when they want to listen in private. For example, when my husband is watching his beloved Red Sox on TV and I want to be watching an art film on Amazon Prime on my iPad, I simply insert my noise-isolation earbuds and watch the movie in peace.
After reading this, you might be wondering: “Why so many systems? Why so many ways to connect? There are many ways to approach the problem of hearing at a distance and in noise. And there is no legislation stipulating which way is the best (at least not yet). It is confusing, not only for you the consumer, but also for hearing health care professionals. Not everyone has the training necessary to help you assess your listening needs so that the best technology can be recommended that will meet these needs as well as your budget. What is needed is a universal way of connecting people to the various sounds that they need to hear. I’m not sure that this will happen in my lifetime, but be assured that there are people are working on it.
Cynthia Compton-Conley Ph. D. is a Board Certified Doctor of Audiology, Professor of Audiology, Hearing Industry Consultant and Host of the Hearing Loss Help Forum. Dr. Cynthia is a retired Professor of Audiology who taught in the graduate school at federally-funded Gallaudet University for 32 years and retired in the CSRS system. In 2013 she founded Compton-Conley Consulting.
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Last 5 posts by Cynthia Compton-Conley
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