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Educational ALDs

Roger System Basics for the Educational Setting

Today's modern classroom is a noisy place.  For a student with a hearing loss the classroom is actually a Hearing Hotspot Phone Imagehostile or toxic listening environment from which they receive very limited acoustical instruction.  This is do partly because of the way we build today's classrooms (hard surface walls, large glass windows, tile or concrete floors, etc.   And partly do to the laws of physics for acoustical properties which states that every time we double the distance between the speaker and listener we drop or lose 6 decibels (dB) in volume.  The average adult male teacher speaks at 65 dB SPL and the average adult female teacher speaks at 62 dB SPL at a distance of 3-feet from their lips.   The average noise floor in a classroom is between 56 dB SPL and 60 dB SPL.  The first row of seats in a classroom is about 6-8 feet from the teacher and the last row is approximately 24-30 feet from the teacher.  Using the shorter distances and computing the voice volume for a female teacher we then have at the first row the average a voice volume of 56 dB SPL and at the last row a voice volume of 44 dB SPL.  For the best understanding a normal hearing person needs +10 dB Signal to Noise Ratio (SNR).  Below this point they can function but are working very hard to follow what is  being said.   For a student with a mild to moderate hearing loss the ratio should be +20 dB SNR.   At 6 feet we have a ratio of 56 dB SPL for the teacher's voice with a noise floor of 56 dB SPL giving us a 0 SNR and at 24 feet we have a -12 dB SNR.  Even normal hearing students, in the back half of a classroom struggle to understand what the teacher is saying.  To overcome this problem we look toward an Roger system for hard of hearing students and soundfield systems to help normal hearing students. 

The Purpose of an Roger System

In the past we have used FM systems to meet the special needs of students in the classroom but with the advent of the Roger system which uses new and improved digital techniques to improve clarity for the student.  The Roger system is uniquely designed to capture the teacher's voice close to their lips, 1-18 inches, before the room noise can blend with the voice and move the teacher's voice electronically to hard of hearing student's hearing aid were it is then amplified in such a way that the student will receive maximum benefit from what is said by the teacher.   This lets us work around the laws of physics and the inverse square law for acoustics.  We now provide the +20 dB SNR, needed by a hard of hearing student, to follow an oral discussion without being totally exhausted before half the day is over.  

The Roger System

The Roger system is composed of two basic parts, the transmitter and the receiver, plus a method of coupling the receiver to the students ear, hearing aid or cochlear implant.   Since most hard of hearing students wear hearing aids or a cochlear implant (CI) the coupling is generally done through a form of magnetic induction or by direct coupling, called Direct Audio Input or DAI. 

Roger Transmitter: 

  •  Generally a small, battery powered, package that has a microphoneZoomlink +
    • The microphone is a separate piece that can be either a head-worn boom microphone (best option) or a lapel / lavaliere style that clips on the clothing about 8-18 below the mouth.
    • Some of the transmitters have a mute switch so the transmission can be muted when the teacher is talking to just one student or small group and does not want the voice to carry to the hard of hearing student.  This type of transmitter is depicted above
    • +
  • Roger PenThere is a new type of Roger transmitter now on the scene.  This is the Roger pen.  This microphone, when held is a very directional microphone, about a 60° pickup arc, that is great for use in small groups in noisy listening environments or when worn around the neck on a lanyard but when the microphone is placed on a flat surface it becomes an Omni-directional pickup.  It should be noted that the Roger line of products are not compatible with the installed base of standard FM products.

Roger Receivers

  • There are three styles of Roger receiver/ a body-worn receiver, a neck-worn receiver and a direct connect to a persons own hearing aids using either a DAI euro-coupler or an integrated receiver that becomes part of the hearing aid.
  • Generally the body-worn Roger receivers are used mainly for Assistive Listening Devices in auditoriums and public meetings and not used much in the school setting. 
  • The smaller around the neck receiver (Phonak's MyLink+) can connect to a person using either the built-in neckloop or a set of headphones can be attached to the receiver.  The headphone option is great for teachers and staff to check the receiver to see if it is working correctly.
  • The DAI receivers connect directly to a persons hearing aid or cochlear implant.
  • on DAI inputs the hearing aid must be programmed for the Roger receiver by the student's dispenser or audiologist before the Roger receiver is to be used.  With students having cochlear implants the CI processor must  be mapped for the DAI receiver.  If this is not done the receivers will not work for the student.  

Important Note about Telecoils vs. DAI

As explained earlier, a telecoil, also called a T-coil or Induction coil, is designed to pickup a fluxing magnetic field, generated by an induction loop or neckloop, and feed the signal into a person's hearing aid or CI.  The difference between an induction loop and a neckloop is the induction loop is designed to cover an area or classroom while the neckloop does the same thing on a more personal level, generating the field just around the head and neck of the person. 

Roger vs. FM Products

  • Educational FM equipment operates on the 216-217 MHz band set aside by the FCC for assistive listening devices only in the USA.  No other radio devices may operate on this band.  Other countries have set aside other frequency bands for Roger devices.  Devices bought for the US market may not work effectively in other countries.  If you are buying for a country other than the US market please let us know so we can check frequencies to insure compatibility.
  • Roger products are using the 2.4 GHz band  using Digital Spread Spectrum (DSS) to insure clean channels of operation.  The 2.4 GHz band is set by international standards and will work, without interference, any where in the world. 
  • The two bands are not compatible with one another.  If you are buying to work with an installed base of standard FM transmitters and receivers you should stay within the bands of your existing equipment.  If you are not worried about backwards compatibility then it is my recommendation that you start the move to the newer Roger class of equipment.