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Assistive Listening Systems

John McJunkin • October 2020Sound Sanctuary • October 11, 2020

We use a lot of technology to help people hear all the details of our services — worship music, announcements and, of course, the message. We do a pretty good job, and we’ve even achieved sophistication to the point of directing sound toward very specific areas with magical cutting-edge speaker technology so the sound reaches every part of the room.

However, this process presumes everyone in the room has regular and naturally sufficient hearing, which is not the case for everyone. In fact, if we’re honest, the quality of our hearing begins to deteriorate pretty much immediately after birth, and seems to accelerate once we reach our twilight years. Due to this inconsistency in the quality of hearing throughout our congregation, we must ensure everyone hears what we’re presenting. This is important enough that the federal government has deemed it worthy of action. The Americans with Disabilities Act (ADA; ada.gov) requires that public spaces where people congregate for presentations must provide solutions for improved and clearer sound to those who suffer hearing loss. The ADA spells out the number of patrons (or congregants) the public space must serve with assistive listening, based upon the total number of seats. The expectation is that the more seats, the greater the assistive listening capacity. The good news is that tax deductions and tax credits are available to help fund the installation of these systems, and the systems improve what we do, so it’s a win-win all the way around. And government mandates aside, we simply want the people who attend our services to hear everything clearly, so it’s a worthwhile pursuit.

‡‡         Choices and Decisions

Once a decision to pursue assistive listening is reached, the system type must be selected. These fall into four basic approaches: RF, IR, loop and Wi-Fi. RF employs good, old-fashioned radio waves carrying the signal to our listeners, each of them with their own receiver. IR works similarly, using infrared light to carry the signal to each listener. Loop systems are also RF, strictly speaking, albeit a bit different. Standard RF requires a transmitter and a receiver, both tuned to the same frequency. Loop systems employ a loop of copper wire or tape placed around (and sometimes through) the space, radiating sufficient electromagnetic energy to induce current in “telecoils” or “t-coils” in hearing aid systems. The energy is actually modulated at audio frequencies and is transduced into audio by the user’s hearing aid. Wi-Fi is the most recent arrival in the world of assistive listening systems, where digital audio is made available via Wi-Fi routers in the space. Bluetooth falls under the rubric of Wi-Fi, but is a less popular solution for a couple of reasons.

RF systems have remained popular over the years because they are less costly than loop systems (largely due to reduced installation costs), and they are reliable. They’re simple to use — we just send our mix to the transmitter, offer receivers to all who wish to have them, and they tune in and get a clear signal. IR systems are similarly easy to use, albeit at a somewhat higher price tag. More expensive to install, loop systems are typically the spendiest option, but are liked, because they literally require no additional hardware; t-coil-equipped hearing aids can automatically “tune in” to loops without additional gear. And coil-equipped “receivers” can be deployed to provide signal to other devices for those who are not equipped themselves. Bluetooth might seem like a logical and likely solution, but the pairing that it requires becomes a bit problematic if there are many potential listeners, and it can exhibit substantial latency as well. Wi-Fi, particularly when used in BYOD (bring your own device) mode — with smartphones, for instance — is gaining in popularity.

In the spring of 2020, those who were not already streaming their services online were tossed into the lake and had to quickly learn to swim. Now, a few months later, we have (hopefully) gotten these things sorted out, and among the most important attributes of that process is the notion that the broadcast stream must be discrete and separate from the mix feeding the main P.A. speakers in our sanctuary.

I visited that notion in my April, 2020 column, where I noted that our FOH mix takes into consideration the acoustical energy of certain loud musical instruments (typically drums, but amplified guitars/basses as well). These loud elements don’t need to be amplified by our FOH system as much as quieter elements like vocals or keyboards or acoustical instruments. The FOH mix, (when isolated from the sanctuary’s acoustical space), probably sounds terrible — with drums and any other loud sources noticeably under-represented, and quiet stuff over-represented. At FOH, we are striking a balance between two different types of elements. A result of this phenomenon, we cannot route our main FOH P.A. mix directly to the assistive listening system, although a separate streaming feed may be a better choice. Every house of worship should move toward that goal as soon as it’s plausible, to present an online streaming experience that’s nearly as good as the in-person experience.

In fact, for sophisticated operations, establishing more than one kind of assistive listening mix makes sense. With RF or IR systems, we typically have control over what kind of transducer actually delivers audio… over-ear headphones or earbuds. If so, we can tailor the bandwidth of our mix to the reproduction capacity of the end transducer. However, with loop systems, we must presume that the bandwidth of users’ transducers will be somewhat limited, and band-limit our mix accordingly. In particular, we’ll probably need to apply a high-pass filter to limit the amount of deep low-end. Another consideration in developing our special mixes is intelligibility. The spoken word is our most important content, and we should focus our attention on presenting it as clearly as possible. Boosting the intelligibility frequencies in the upper mids can help ensure that the hearing impaired can clearly make out what is being said. Another consideration? Sometimes the hearing impaired will turn up their personal devices to levels that are audible by those seated around them. If the timing of the signal is such that the signal arrives earlier than the sound heard by those without assistive listening, it can be perceived as obnoxious — preceding what’s heard from our FOH loudspeakers. In that case, the assistive listening audio should be delayed, just as we’d delay speaker towers in a stadium.

Assistive listening systems are strongly encouraged by law, but we should provide this service for the right reason — to ensure everyone can hear the message clearly. A little research and effort can help make it happen with a minimum of difficulty and out-of-pocket expenditure. Give it some consideration!

John McJunkin is the chief engineer and staff producer in the studio at Grand Canyon University.

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