Telecoil Roundtable Discussion

How much does a loop system cost for a typical church or movie theater?

Mark: The costs vary depending upon the type of installation and facility. I believe that the average cost of installation in an average-sized church is around $2000. You can obtain details from the Website www.hearingloop.org. David: Fifteen years ago we installed an auditorium loop system in a hospital a couple of miles from here. This was for a presentation by Self-Help for the Hard of Hearing (SHHH). We went in one Saturday with the appropriate wire and looped it for about $140. This cost included all cables and connectors to bridge the output of the existing sound-reinforcement (PA) system and a dedicated power amplifier for the loop. People liked the system from the outset and it still is in use today. For best results, it is necessary to use a wire loop that has an adequate total impedance to match the specified load impedance of the power amplifier. The impedance of a given length of wire increases as the wire gets thinner. You can measure impedance easily, and thus select the correct gauge of wire. We found that the patients who had been using other assistive listening systems said that “suddenly the sound was inside of their heads” and that they could hear so much better. Just one caveat, though: you need to make sure that the whole system is compatible with the sound-reinforcement system in the auditorium. Audience member: The major loop manufacturers make very good loop receivers for people with mild or moderate hearing loss. They consist of a receiver and headphones and interface with an existing PA system. As a result you save a lot of money by using the amplifier that's already built in to the PA system. They cost around $700 to loop a large auditorium, in contrast to stand-alone loops which cost nearer $2000 or $3000.

Are loop systems for private use in the home available commercially? What is the source and cost?

Mark: There are quite a few different systems for home use available commercially, such as loops, infrared, and frequency modulation (FM) systems. I have tried many of them. All are good, but I have found loop systems to be the most convenient. Loop systems for the home are available for between $500 and $600 from, for instance, Oval Window, Oticon, and several other vendors. It is possible to loop virtually anything. I know people with loops in cars and someone who has their whole house looped. In London, there are even taxis and tour buses that are looped. The key to having an effective loop system is good microphone technique. David: If you are contemplating making a loop system for yourself, you don't need to string out 40 meters of wire to get the correct load impedance. You can buy standard ribbon cable used in computer hookups. This flat cable is made up of 4 to 32 parallel wires. If 5 m of one of the wires has a DC resistance of 1 ohm, and you need a total resistance of 8 ohms, you can separate a 5-m segment of 8 wires from the ribbon. Then, you can strip off the insulation from each wire at each end and splice all the ends together except the first and the last. This will yield a total resistance of 1 ohm × 8 = 8 ohms and produce a compact loop that can be used in a smaller area.

Are there any possible health concerns with T-coils and other systems located in close proximity to the skull?

Mark: I have looked into whether there are health effects to teachers wearing FM systems and people wearing loops. There do not appear to be any deleterious health effects with these systems. Harry: Loop systems do not use very strong electromagnetic fields, and thus are not a concern; the same goes for the transmitters of FM systems. Cellular telephones, however, do use relatively powerful transmitters. Standards have been published which specify the maximum allowable power of the radio transmission that is safe for humans. These standards have been implemented to ensure that the levels of the electromagnetic signals emitted from cellular telephones and other systems, such as the electromagnetic leakage from television sets or microwave ovens, are safe. Every now and then you hear a story about cellular telephones causing brain cancer. This is only likely to occur, however, if you had 100 cellular telephones wrapped around your head! Cellular telephones have been around for over 20 years and there is no evidence of cancer or any other negative effects. David: A T-coil cannot be a problem because it simply picks up signals. It does not have a transmitter and thus there is no electromagnetic radiation.

Should T-coils be used bilaterally or unilaterally to take best advantage of the loop?

Mark: I would suggest bilaterally. David: Remember though, if the binaural T-coils are not in phase, the percept of the sound will be out at the ears instead of being in the middle of the head.

How can you reduce the “buzz” that occurs when the strength of a T-coil is increased?

David: Often, the buzz you hear is electromagnetic radiation from a source other than the telephone, such as a computer monitor, a power supply, or fluorescent lamps. It is simple to locate the source. Attach a behind-the-ear hearing aid (BTE) to your stethoscope, switch the BTE to the T-position, and move it close to the possible sources of electromagnetic radiation. The buzz will increase when you are close to the source. A real problem comes, however, when your job requires you to use both a telephone and a computer. What do you do then? Does someone else have a suggestion? Audience member: Use an LCD monitor, instead of a CRT. David: That will work for radiation from the monitor, but first you'll need to take out a bank loan! Audience member: One way to decrease the interference between the loop and the hearing aid is to increase the signal from the source that is generating the loop signal while decreasing the hearing aid gain using the volume control. That way you can ensure that you have a stronger signal than the 60-Hz interference. This is not an ideal solution, of course, but it does work. However, as David Lilly said before, an office environment is especially problematic for use of a T-coil due to interference from the fluorescent lighting and monitors all around. These sources of interference are virtually impossible to eliminate. David: Yes, a major problem in this country is 60-Hz interference, while in Europe it is 50-Hz interference. Your suggestion to increase the gain of the power amplifier driving the loop is a good one; this will reduce much of the interference. Additionally, you can use a stand-alone telephone amplifier so that you can control the gain independently. Another solution is to cut the gain of very low-frequency signals in your programmable hearing aids. This often will cut out a lot of the interference.

Some patients have success using a neck loop for their cell phones, and others do not due to interfering noise and distortion. Why is this?

Harry: The interference can come from two sources. One is associated with the position of the T-coil relative to the direction of the magnetic field within the loop. It must be at the correct angle for the magnetic field. If it isn't adjusted just right, you get a poor, noisy signal. But with practice, one can learn to make the necessary adjustment to get a good signal with little or no interference. The second source of interference is due to the interaction between the radio transmissions of the cellular telephone and the electronics of the hearing aid. Older hearing aids with less immunity to electromagnetic transmissions can pick up substantial amounts of this interference. Note that this interference is picked up by the electronics of the hearing aid and is not limited to the T-coil. It is easy to differentiate between these two types of interference. If the interference is picked up by the electronics of the hearing aid, the interference will increase dramatically when the cellular telephone is brought closer to the hearing aid. One of the advantages of using a neck loop is that the cellular telephone need not be held close to the hearing aid, thereby reducing or eliminating this form of interference. If the interference is caused by a misalignment of the T-coil with the direction of the neck loop's magnetic field, changing the location of the cellular telephone will not change the degree of interference, but changing the relative positions of the hearing aid and neck loop so as to align the T-coil with the magnetic field will reduce the background interference and improve the level of the signal.

Dr. Ross told us that loop systems are very common in Europe. Are data showing that people in Europe are satisfied with the fact that many public places are looped?

Mark: I don't know if there are data on this. But, if hearing-impaired persons can go into most public places and have a signal available to them, they are probably very satisfied. I certainly would be and I shouldn't think I am an exception. David: We are fortunate to have some visitors here from Europe-Charlotte from Denmark, Ann-Catherine from Sweden, and some representatives from European hearing-aid manufacturers. From what they and from what other European colleagues have told me, there is good acceptance of loop systems in their countries. Charlotte: I don't know of any statistical data either, but it is my impression that people who use loop systems in various public places in Denmark are very satisfied with the systems. Ann-Catherine: The same goes for Sweden. David: Well, if we have Danes and Swedes agreeing, it must be true!

Are loop systems in Europe funded privately or by the government?

Charlotte: Loop systems in public places are installed because it is mandated by law, not due to magnanimous behavior!

Is there an organization in this country advocating for loop systems in public places?

Mark: Yes, Self-Help for Hard of Hearing People (SHHH) is active in this arena and in many other aspects of advocating for the hearing impaired. I write a column for them every couple of months. I suggest that you tell all of your adult clients about SHHH as they are in the forefront of many issues associated with helping the hearing impaired.

What do the panel members consider to be the best ways to enhance classroom communication both between a hearing-impaired teacher and normal hearing children and vice versa?

Harry: There is a movement to improve communication in classrooms and there is still much room for improvement. One method is to improve classroom acoustics by reducing the reverberation and ambient noise caused by reflections off the walls, ceiling, and other hard surfaces in the classroom. Acoustic tiles and other sound-absorbing materials are commonly used for this purpose. It is an effective although expensive approach and is not a complete solution for large classrooms. A second approach is to use a sound reinforcement system. These systems are essentially acoustic amplifiers that increase the level of the acoustic signal reaching the student. These systems are very useful in large classrooms, including those that have been acoustically treated for reverberation, since the level of the teacher's voice is relatively low for students at some distance from the teacher. Mark: As a hearing-impaired professor, my options have been limited to moving close to the individual asking the question, or having the individual speak more loudly. This doesn't work well for elementary school children though. I still don't have a good answer. We used to recommend having the students use a pass-around microphone but that's not too practical. Pointable array microphones help in a small classroom but not in a large auditorium or lecture theater. Audience member: I had a patient who was a graduate student teaching assistant. He taped an FM transmitter to a radio-operated car that he would drive up to the student asking the question. The students loved it. Audience member: There is a Web site (www.beyondhearingaids.com) that provides a lot of interesting information about approaches to using assistive devices in all sorts of situations. It might provide some interesting ideas.

Is sound field FM a good solution for the classroom?

Mark: Sound field FM certainly helps the hearing-impaired child but does not help a hearing-impaired teacher. A dual-microphone system is an option but the children need to pass the microphone around. Perhaps the solution is to implement what a group called the “Indian Guides” used-a talking stick! Basically, only the person holding the stick (microphone) was permitted to speak. Amazingly the kids followed this rule. This would help all the children in the classroom, as well as the teacher.

Instead of asking hearing aid manufacturers for improved T-coils, should we be requesting a different solution?

David: Some hearing aid companies already have introduced an alternative approach. They have developed adaptive routines in software for the real-time cancellation or suppression of feedback. These systems enable the use of telephones without the need for a T-coil. Harry: This is a very good question because we are at the threshold of major new advances in technology. However, the situation is this: Loop systems are cheap, they already exist, and their use is growing, particularly in Europe. It is most likely that loop systems and T-coils will be with us for some time. A new wireless technology that one day may challenge the dominance of loop systems is known as Bluetooth ©, named after the Danish king Harald Blåtand (Bluetooth) who improved communication between Denmark and Norway by unifying the two countries. Bluetooth is a short-range, very high-frequency wireless technology that permits digital communication in two directions (i.e., it can both transmit and receive signals on the same wavelength). It is widely used with computers and its use in cellular telephones and other portable digital devices is growing rapidly. A variation of this technology, developed by the entertainment industry, uses one-way radio transmissions and is less expensive than Bluetooth. One of these two systems will dominate eventually. Time will tell which one. The cost of Bluetooth and related technologies is expected to come down substantially as a result of large-scale mass production. Further, the size and power consumption of Bluetooth transmitters and receivers also are expected to be reduced substantially to meet the growing demand for this technology in small, portable digital instruments such as cellular telephones, palmtop organizers, and other handheld digital devices. When Bluetooth technology becomes small enough to be practical for use in hearing aids it will represent a more effective alternative to loop systems and T-coil technology. However, as I said, these are emerging technologies while loop systems already exist and are relatively inexpensive. Loop systems will be with us for the immediate future and probably for some time to come. Mark: The point I made is that I wouldn't know what to ask of the telephone industry, since we already have amplified T-coils. The issue is getting public places looped when they are first built. Consider this auditorium. Had they incorporated a loop system when it was built it could have been hooked directly into the PA system instead of what we currently have, which is a microphone we need to pass around from speaker to speaker. David: Yes, such a system would be simpler for Mark and other hearing-impaired individuals, and it would be transparent to everybody else. Audience member: You could probably interface the output of the PA system to an FM transmitter in addition to the loop. This approach would be useful for patients who don't have T-coils in their hearing aids. David: I believe the statement here is that a loop system is not really a solution for people who don't have telephone coils in their hearing aids. This is true and published data suggest that BTE hearing aids and in-the-ear hearing aids with T-coils are more common in Europe than in the United States. Certainly, adding an FM transmitter or an infrared transmitter and appropriate receivers would be helpful for these people. There is another way that also is useful and inexpensive. We acquired $ 20.00 Radio Shack portable amplifiers and cemented a loop of wire on the inside of the case. Next we added a switch that allows the listener to select between the microphone and the loop. In the microphone position the amplifier is an inexpensive “Pocket Talker” with a wired microphone that can be placed near the talker's lips. In the loop position it picks up the electromagnetic radiation from the loop in the room or from the telephone. The output from the amplifier then can be delivered to a pair of earphones or to the audio input of a hearing aid.