FM and Soundfield Systems

I want to start this post by saying that BOTH FM Systems and Soundfield Systems can be excellent options for students with hearing loss.  Both devices function to increase the signal-to-noise ratio, making the relevant signal (i.e. the teacher’s voice) louder than the noise and distraction (i.e. other children talking, chairs scraping the floor, etc.).  There are differences, however.

An ear-level FM System transmits sound directly from the teacher’s microphone (worn as a headset, lapel, or lavaliere… more on this below) to a “boot” or “shoe” attached to the child’s hearing aid, cochlear implant, or Baha.  Other receiver types include a lavaliere-style neckloop or a separate FM earmold system (the former is not so commonly used anymore).

 

Soundfield System

A soundfield system uses the same types of microphones, but transmits instead to speakers placed around the room or a portable speaker (about the size of a brick — but not as heavy!) that can be placed on the child’s desk and travel around the classroom with him.

 

I have used, and had success with, both types of systems for a variety of students with hearing loss.  However, I think one of the greatest issues to consider when deciding between the two systems is, “IS THE CHILD A GOOD REPORTER?” With FM systems that connect to hearing aids, it is possible for adults to listen to the FM+HA signal through the stetheset test headphones.  For a CI, however, parents/teachers/therapists are only able to test the microphone quality (and even that’s not what the child actually “hears”), NOT the FM+CI condition.  If you are considering an FM system for a child with cochlear implants, especially a very young child or a child who, for multiple disabilities, newness of implant, or any other reason, is not yet a reliable reporter of sound quality, adults must be extra vigilant to note any changes in the child’s hearing. If the FM signal is weak or static-y, a “poor reporter” will not be able to tell you this, which could lead to hours or days of reduced sound input with no one even knowing. Objective measures, such as testing the child’s hearing in noise in a soundbooth in the unaided, CI, and CI+FM conditions, can yield data that indicate whether or not the child is benefitting from the FM system, but on a day-to-day basis, a child who cannot reliably report the sound quality coming through the FM presents an extra challenge for parents and professionals.  With a soundfield, the sound from the microphone is broadcast through speakers that anyone so anyone can hear and monitor quality without extra equipment.  This might be a better choice for a young/new cochlear implant user who is not yet ready to troubleshoot her own device.

 

 

MICROPHONE TYPES

• Lapel: the microphone clips to the speaker’s lapel

• Lavaliere/Pendant: the microphone is worn like a necklace and hangs from the speaker’s neck

• Headset/ Boom (aka “The Madonna” or “The Britney Spears” — a real generation gap test!): the microphone is worn around the head/ears and projects out over the mouth

• Pass-Around (aka “The Oprah”): a wireless, typical microphone to be passed around for class discussions, usually used in addition to one of the three microphone types above, for secondary speaker(s)

 

Lapel Mic		Headset/Boom Microphone		Pass-Around Microphone

Of all of these microphones, the Headset/ Boom Microphone option gets the mic closest to the speaker’s voice.  In addition, this type of microphone moves with the speaker’s face, whereas the other microphone types remain in place.  When the teacher turns her head, her voice is directed away from the lapel or lavaliere microphone, and the student temporarily loses the signal.  By placing the mic right by the teacher’s lips, as in the headset/boom mic option, you ensure constant access to sound.  For older children in seminar-style courses or classes with lots of group discussion, adding a pass-around microphone may help a student with hearing loss follow dialogue from multiple speakers as the mic is passed back and forth around the room.

TIPS AND THINGS TO REMEMBER

• Make sure the transmitter (worn by the speaker) is on the same channel as the child’s receiver (attached to his device).

• Teachers can wear the transmitter in a pocket, attached to a belt loop or waistband, or worn in a special pack — careful not to let it fall to the ground when bending over!

• Teachers should be sure to turn off the FM/Soundfield system when leaving the classroom or having private discussions.

• Ling checks should be performed with and without the FM systems multiple times EVERY DAY to ensure clarity of signal.

• Remember that classroom amplification can benefit ALL children, not just those with severe-profound hearing losses.  Other groups shown to benefit from amplification include: children with minimal or unilateral hearing loss, children with transient hearing loss due to ear infections, children with ADD/ADHD, English language learners, and more!

• The FM/Soundfield is only useful when it’s being used!  Spot-checks in the classroom by the parent, SLP, or TOD can help to “encourage” teacher compliance with assistive technology use and serve as resources for troubleshooting.  Remember, if it’s in the IEP, it’s mandated by law that the child’s teacher comply with its use!

RESEARCH IN SUPPORT OF FM AND SOUNDFIELD SYSTEMS

• The Benefits of Sound-field Classroom Amplification

• Classroom Management of Children with Minimal Hearing Loss

• Classroom Amplification Technology: Theory and Practice

• Acoustical Barriers to Learning: Children At Risk in Every Classroom

• Classroom Amplification to Enhance Student Performance

• The Use of Soundfield Amplification of the Teacher’s Voice in the Regular Education Classroom

• Classroom Amplification: Not Just for the Hearing Impaired Anymore

• Soundfield-FM Amplification: Theory and Practical Applications

• Rationale and Use of Soundfield Systems

Images provided courtesy of Lightspeed Technologies, Inc.