Assistive Listening Devices for the Classroom

The issue

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Inclusion in the general education classroom has opened doors for deaf and hard-of-hearing (DHH) students across the globe.  The benefits of inclusion are numerous; however, communication in the classroom can present obstacles when students utilize different communication modalities.  More and more DHH students are enrolling in mainstream programs where the majority of information is delivered via spoken language.  Access to spoken language through listening presents challenges that revolve around three basic acoustic factors: noise (any unwanted signal/sound), reverberation (echo), and distance from the speaker/teacher.  The classroom must be modified to accommodate for these acoustic barriers.

What we know and what we don’t know

There are a variety of ways to adapt the environment to reduce negative effects of these three phenomena.  These include, but are not limited to, classroom alterations such as carpeting, acoustic wall/ceiling tiles, curtains, cork boards, sound barrier walls, and hanging students work around the room.  Many of these are inexpensive and can be done in any room.  These solutions can reduce the negative impact on speech recognition, but by only fractions.  The best practice for overcoming unfavorable acoustics is assistive technology.

While there are different options for assistive technology, the basic premise is the same for all.  The teacher or speaker wears a microphone and transmitter.  The student or listener wears a receiver that is coupled to their hearing aid(s) and/or cochlear implant(s).  The spoken signal is transmitted via FM radio waves from the teacher to the student, across the 2.16MHz band.  The radio frequencies used in education are dedicated bands to prevent channel interaction from other FM broadcasting.  It is important to remember that educational channels can interfere with other educational channels and an audiologist can help to properly establish dedicated channels for each classroom.

  • Traditional FM is an analog signal.  The system provides around a 10dB FM advantage to the signal to noise ratio (SNR, or how much louder the signal is than background noise).  When the noise level in the classroom changes, the SNR changes accordingly.  This means that an increase in room noise the SNR will simultaneously decrease.
  • Dynamic FM is also an analog signal.  The microphone is constantly measuring the noise levels of the room.  When noise levels increase, gain (loudness) is increased in the receiver, maintaining a better SNR.

Roger is the newest solution to the combating poor classroom acoustics.  Roger operates along the 2.4GHz band and is a fully digital signal.  The 2.4GHz band is globally license free; any Roger system can be used around the globe.  Additionally, there are no channels to program and therefore no interference with neighboring channels.  This allows for Roger systems to be used simultaneously by adjacent classrooms without the concern of competing signals.  The microphone in this system is adaptive, similar to Dynamic FM, maintaining a positive SNR.  When comparing speech recognition between options, Roger users saw a 54% improvement over traditional FM and 35% improvement over Dynamic FM.

With any FM or Roger system there are a variety of transmitter, receiver, and accessory options available to the listener.  The choices depend on the age of the student, classroom arrangement and format, and other technologies present in the classroom.

Transmitters

  • FM or Roger Inspiro Transmitter: Robust design for durability in the classroom.
  • Roger Touch Screen Microphone or Roger Pen: The most versatile option with advantages both in and outside the classroom.  Microphone focus depends on the orientation of the device, using an accelerometer:  Vertical for 1:1 interaction, horizontal for small groups, and diagonal for interview (pointing at a speaker/teacher).  Bluetooth functionality can pair to cell phone and other Bluetooth-compatible devices.
  • Table Mic: For small group situations.

Receivers

  • Dynamic Soundfield: Speakers within the classroom where all students have access, including hearing classmates.
  • Individual Receivers (integrated receivers, Roger X, myLink): Ear level receivers that work directly with students’ personal devices.
  • Focus: Ear level receivers that function as headphones for hearing students.

Accessories

  • Pass Around Microphone: Microphone that is passed around to different speakers in the classroom.
  • Multimedia Hub: Used for all classroom media options, providing equal access to supportive materials.

Implications

It is imperative that DHH students who rely on spoken language be given the best access in all situations.  FM or Roger systems make that possible, with a wide variety of solutions.  While FM and Roger devices can be expensive, they are deemed to be reasonable accommodations under the Americans with Disability Act.  Technology is advancing at a rapid pace and access in the classroom is just one of the many benefits.

Posted on Oct 6, 2016 by
Amanda Picioli
Department of Communication Studies and Services
National Technical Institute for the Deaf
aldnce {at} rit.edu

Further reading