fm systems for school aged children n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
FM Systems for School Aged Children PowerPoint Presentation
Download Presentation
FM Systems for School Aged Children

Loading in 2 Seconds...

play fullscreen
1 / 85

FM Systems for School Aged Children - PowerPoint PPT Presentation


  • 549 Views
  • Uploaded on

FM Systems for School Aged Children. Linda Thibodeau, Ph.D. Advanced Hearing Research Center Callier Center for Communication Disorders University of Texas at Dallas. Supportive information May be obtained at the Website of Linda Thibodeau www. utdallas.edu/~thib.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'FM Systems for School Aged Children' - oshin


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
fm systems for school aged children

FM Systemsfor School Aged Children

Linda Thibodeau, Ph.D.

Advanced Hearing Research Center

Callier Center for Communication Disorders

University of Texas at Dallas

Copyright by Linda M. Thibodeau 2005

slide2

Supportive information

May be obtained at the

Website of Linda Thibodeau

www.utdallas.edu/~thib

Copyright by Linda M. Thibodeau 2005

welcome to this lecture on fm systems
Welcome to this lecture on FM Systems!

I hope you will find this information interesting and rewarding as you learn of the significant differences that can be achieved with

FM Systems!

Copyright by Linda M. Thibodeau 2005

overview
OVERVIEW

1. Rationale for use of FM Systems

2. FM Systems

3. FM Evaluation Procedures

4. Use of FM Systems

Copyright by Linda M. Thibodeau 2005

slide5
Let’s start with the Rationale for using FM Systems.

Copyright by Linda M. Thibodeau 2005

1 rationale for use of fm systems
1. Rationale for use of FM Systems

A. Signal-to-Noise Ratio

B. Typical Classroom Noise

C. Audio Demonstration of

Classroom Noise

Copyright by Linda M. Thibodeau 2005

signal to noise ratio
Signal-to-Noise Ratio

A major problem for all persons with hearing loss is….Listening in Noise !

The problem is described by the

signal-to-noise ratio or SNR.

The amount of “Signal,”

what you WANT to hear

. . .compared to. . .

“Noise”,

ANY sound you don’t want to hear.

Copyright by Linda M. Thibodeau 2005

in a large group distance and noise can be a problem
In a large group, distance and noise can be a problem.

Copyright by Linda M. Thibodeau 2005

this results in a poor signal to noise ratio
This results in a poor signal-to-noise ratio.

Copyright by Linda M. Thibodeau 2005

i e the intensity of the noise at the listener s ear is greater than the signal of the speaker
i.e. the intensity of the noise at the listener’s ear is greater than the signal of the speaker.

Copyright by Linda M. Thibodeau 2005

a poor s n ratio is 10 db
A poor S/N ratio is -10 dB
  • the noise is 10 dB more intense than the signal

80 dB

70 dB

Copyright by Linda M. Thibodeau 2005

a good s n ratio is 20 db
A good S/N ratio is +20 dB
  • the signal is 20 dB more intense than the noise

70 dB

90 dB

Copyright by Linda M. Thibodeau 2005

slide13
So...ideally we want to have a positive S/N ratio and a constant signal level regardless of distance between the speaker and the listener.

Copyright by Linda M. Thibodeau 2005

slide14
We can accomplish this by placing a microphone on the speaker and delivering the sound directly to the listener.

Copyright by Linda M. Thibodeau 2005

b typical classroom noise
B. Typical Classroom Noise
  • Optimal noise level
  • for a class with students with hearing loss would be
  • 30-35 dBA,
  • yet the typical level is about
  • 60 dBA.
  • Average conversational speech is about 60 dBA, which means the SNR is often 0 dB!
  • (ASHA, 2005)

Copyright by Linda M. Thibodeau 2005

slide16

The optimal SNR for teaching students with hearing loss would be +15 dB,

  • (the teacher’s voice is 15 dB more intense than the background noise).
  • However, the typical SNR in classrooms is only about
  • +5 to – 7 dB!
  • (ASHA, 2005)

Copyright by Linda M. Thibodeau 2005

effects of noise on speech recognition
Effects of Noise on Speech Recognition

Finitzo-Heiber and Tillman (1978) measured the effects of noise and reverberation on speech recognition scores with 8 to 12 year old

children with

Normal Hearing and Hearing loss .

Copyright by Linda M. Thibodeau 2005

slide18
In a soundbooth:

No Noise, Little Reverberation

Children with Normal Hearing scored

95% - Only missed 5% of words

Children who were Hard of Hearing scored = 83% - Only missed 17% of words

Copyright by Linda M. Thibodeau 2005

slide19
In a situation similar to a typical classroom:

Normal Hard of

Hearing Hearing

SNR of +12 dB: 83% 60%

SNR of 0 dB: 48% 28%

These results suggest that children with hearing loss may only be hearing about one fourth of speech in a typical

noisy classroom.

Copyright by Linda M. Thibodeau 2005

c audio demonstration of classroom noise
C. Audio Demonstration of Classroom Noise
  • Click on each loudspeaker to hear:
  • Typical Classroom Noise
  • A teacher reads a story in a classroom with a typical SNR
  • Same teacher reads a story in
  • an optimal SNR provided by
  • using an FM System

Copyright by Linda M. Thibodeau 2005

slide21
Now let’s look at the operation and design of FM Systems in our

second section of the lecture.

Copyright by Linda M. Thibodeau 2005

2 fm systems
2. FM Systems

A. Introduction to FM Technology

B. Transmitters/Microphones

C. Receivers/Sound Transducers

D. Cochlear Implants and FM Systems

Copyright by Linda M. Thibodeau 2005

slide23

A. Introduction to FM Technology

FM Systems use a frequency-modulated

signal to transmit the speech through the

air similar to an FM Radio station.

The system involves a microphone and

transmitter on the speaker and a receiver

for the listener with some type of

sound transducer.

Copyright by Linda M. Thibodeau 2005

slide24

All FM systems have these parts-

Microphone

Transmitter

Receiver

Sound Transducer

Copyright by Linda M. Thibodeau 2005

slide25

FM Transmission Process

3) Voltage fluctua-

tions produce fluctuations of electric and magnetic fields around the antenna at

a specific frequency

1) Speaker talks into

microphone which

generates rapid

fluctuations of

voltage

2) Voltage fluctuations are passed to a transmitting antenna

5) Electromagnetic

waves produce

fluctuations in voltage at a

receiving antenna

4) Electric and

Magnetic field

fluctuations travel

as electromagnetic

waves

6) The voltage fluctuations are amplified

8) The voltage

fluctuations in that frequency range are

sent to the

acoustic transducer

9) The transducer

converts the voltage

fluctuations into

sound waves to

go to the ear

7) A filter selectsthe frequency of interest

Copyright by Linda M. Thibodeau 2005

slide26

Transmitting Frequencies

  • Typically each transmitter is assigned a frequency,
  • also called a channel. These may be coded by numbers,
  • colors, or letters. The channel component may be
  • called an oscillator.
  • Examples:
  • Number Color Letter Trans. Freq.
      • #1 Red/Gray A 72.000-72.025
      • #2 Brown/Gray B 72.025-72.075
      • There may be as many as 40 different channels used
      • in a school.

Copyright by Linda M. Thibodeau 2005

slide27
Now let’s look more closely at the Transmitter/Microphone features….

Copyright by Linda M. Thibodeau 2005

b fm transmitters microphones
B. FM Transmitters/Microphones

Descriptive Categories

1) Microphone Type

2) Microphone Location

3) Channel Options

Copyright by Linda M. Thibodeau 2005

fm transmitters microphones
FM Transmitters/Microphones

Microphone Type:

The microphone characteristics can vary.

Omni-directional Microphone-

picks up sound from all around

Directional Microphone-

picks up sound primarily from the top

Multi-DirectionalMicrophone-

picks up sound from all around OR focused area

Copyright by Linda M. Thibodeau 2005

fm transmitters microphones1
FM Transmitters/Microphones

Microphone Location:

All Transmitters are worn on the body, but the microphone placement may vary.

On the Body

On the Head

On the Lapel

On the Cheek

(also called Boom mic)

Copyright by Linda M. Thibodeau 2005

fm transmitters microphones2
FM Transmitters/Microphones

Channel Options on the transmitters:

Single, but fixed-Oscillator channel set at the factory and cannot be changed Multi-Frequency

Manual frequency selection-Oscillator

can be removed and changed to another frequency

Wireless frequency selection-Channel

is changed digitally

Copyright by Linda M. Thibodeau 2005

wireless channel changeability
Wireless Channel Changeability

1) Direct Frequency Synchronization-

Pressing a button on the transmitter sends a signal to the receiver to synchronize the channel

Ex. Phonak MLxS with Campus S

2) Automatic Frequency Synchronization-

Walking near a plate on the wall that contains transmitter changes the channel to a preset number

Ex. Phonak MLxS with Wall Pilot

Copyright by Linda M. Thibodeau 2005

slide33

Automatic Frequency Synchronization-Students wearing Phonak MLxS walking past Wall Pilot as they enter classroom to get synchronized to the correct frequency for thatclass.

Copyright by Linda M. Thibodeau 2005

other options transmitters
OTHER OPTIONS - Transmitters

Programmable-Allows the channels to be set digitally via a connection to a computer.

Audio Input Jack-An input jack for the audio signal from another source such as a tape player, VCR, or computer.

No FM/Low Battery Lights-Alerts the users that the batteries or FM switches should be checked.

Talk Over-Allows the microphone to be active

even when the transmitter is connected to another audio source such as VCR

Mute Switch-Allows the microphone to be

deactivated so conversations can be private.

Copyright by Linda M. Thibodeau 2005

slide35
Now let’s look more closely at the Receiver/Sound Transducer features….

Copyright by Linda M. Thibodeau 2005

c fm receivers sound transducers
C. FM Receivers/Sound Transducers

Descriptive Categories

1) Type-Relationship to Personal Amplification/Cochlear Implant

2) Receiver Location

3) Channel Options

4) Sound Transducers

Copyright by Linda M. Thibodeau 2005

fm receivers sound transducers
FM Receivers/Sound Transducers

1) Type-Relationship to Personal Amplification/Cochlear Implant

There are two main types with respect to interacting with Personal Devices:

Basic-Does not interface with Hearing aid or Cochlear

Personal-Does interface with Hearing aid or Cochlear Implant

Copyright by Linda M. Thibodeau 2005

fm receivers sound transducers1
FM Receivers/Sound Transducers

2) Receiver Location:

Some FM Receivers interface with a personal hearing aid worn at the ear? (i.e.one that the student wears throughout the day)

Students and parents generally like this option!!!

Some are worn:

On the Body On the Ear

Copyright by Linda M. Thibodeau 2005

fm receivers sound transducers2
FM Receivers/Sound Transducers

3) Channel options on FM Receivers?

Single, but fixed-Oscillator channel set at the factory and cannot be changed

Multi-Frequency

Manual frequency selection-Oscillator

can be removed and changed to another frequency to match transmitter

Wireless frequency selection-Channel

is changed digitally by pressing a

button on the transmitter that is in close

proximity

Copyright by Linda M. Thibodeau 2005

fm receivers sound transducers3
FM Receivers/Sound Transducers
  • Sound Transducers

Two Basic Categories:

Basic System-Child takes off personal hearing aid each day and puts on the FM Receiver that picks up the teacher’s voice AND acts like a hearing aid.

Personal System-Child keeps the personal hearing aid on all day and the FM Receiver is interfaced through one of three arrangements.

Copyright by Linda M. Thibodeau 2005

fm receivers sound transducers4
FM Receivers/Sound Transducers

Basic System Options

Button Earphone with Body-worn FM system

Ear Level FM Receiver with limited power

Soundfield Speaker to set on desktop or

mounted on the wall

FM Amplifier with Behind the Ear hearing aid

Personal System Options

Neckloop with Personal Aid on T Switch

Direct Audio Input with Personal Aid

Silhouette with Personal Aid on T Switch

Copyright by Linda M. Thibodeau 2005

slide42
Let’s look at some illustrations of these different types of sound transducers!

Copyright by Linda M. Thibodeau 2005

button earphone with body worn fm system
Button Earphone with Body-worn FM system

Copyright by Linda M. Thibodeau 2005

basic ear level fm receiver with limited power

EduLink

by Phonak

Basic Ear Level FM Receiver with limited Power

For Persons with Normal hearing, Mild loss, Auditory Processing Disorder

Copyright by Linda M. Thibodeau 2005

soundfield speaker to set on desktop or mounted on the wall
Soundfield Speaker to set on desktop or mounted on the wall

Desktop Speaker

Wall Mounted

Speakers

Copyright by Linda M. Thibodeau 2005

fm amplifier with behind the ear hearing aid
FM Amplifier with Behind the Ear hearing aid

Copyright by Linda M. Thibodeau 2005

neckloop with personal aid on t switch
Neckloop with Personal Aid on T Switch

Copyright by Linda M. Thibodeau 2005

direct audio input with personal aid
Direct Audio Input with Personal Aid

Copyright by Linda M. Thibodeau 2005

silhouette with personal aid on t switch
Silhouette with Personal Aid on T Switch

Copyright by Linda M. Thibodeau 2005

other options fm receivers
OTHER OPTIONS - FM RECEIVERS

Programmable/Digital-Allows the features of the receiver to be set via a connection to the computer which results in more precise control of the FM signal.

Audio Input Jack-Allows a direct electrical connection to a VCR, computer, or tape/CD player.

No FM/Low Battery Lights-Warning lights to indicate the switch settings and/or batteries need checking.

Microphones-When the FM receiver is not interfaced with a personal hearing aid that has a microphone, a microphone will be needed on the FM receiver to pick up the sounds nearby the student but at a lower level than the teacher’s voice.

Copyright by Linda M. Thibodeau 2005

slide51
Now let’s consider interfacing FM System with Cochlear Implants….

Copyright by Linda M. Thibodeau 2005

d cochlear implants and fm systems
D. Cochlear Implants and FM Systems

A child may receive a cochlear implant when they receive no benefit from a hearing aid. After a surgical procedure, they receive sound stimulation through electrical impulses applied directly to the auditory nerve. FM systems can be used with cochlear implants to provide that optimal SNR.

The same FM Transmitters and some of the same FM Receivers can be used.

Electrical Coupling of the FM Receiver to the Cochlear Implant can occur in two arrangements:

Patch cords connect FM Receiver to Cochlear Implant

Direct Plug-in of FM Receiver

Copyright by Linda M. Thibodeau 2005

patch cords connect fm receiver to cochlear implant
Patch cords connect FM Receiver to Cochlear Implant

Cochlear Implant

Ear Level Processor Body Worn Processor

FM Receiver

Copyright by Linda M. Thibodeau 2005

direct plug in of fm receiver
Direct Plug-in of FM Receiver

Cochlear Implant

Speech Processor

FM Receiver

Copyright by Linda M. Thibodeau 2005

slide55
It is very important to evaluate FM Systems to ensure proper settings for maximum benefit. Let’s see how that can be accomplished in our third section of the lecture….

Copyright by Linda M. Thibodeau 2005

3 fm evaluation procedures
3. FM Evaluation Procedures

A. Electroacoustic

B. Real Ear

C. Behavioral

Copyright by Linda M. Thibodeau 2005

a electroacoustic procedures
A. ELECTROACOUSTIC PROCEDURES

ASHA GUIDELINES FOR FITTING AND

MONITORING FM SYSTEMS (1999)

This document provides Recommended Measures to be performed to compare response through amplification settings with and without the FM system.

ELECTROACOUSTIC PROCEDURES

Performed by an Audiologist

Child need not be present, only need child’s

Hearing Aid (HA) and FM System

Very objective, efficient way to set systems

Copyright by Linda M. Thibodeau 2005

slide58

First step is testing the child’s HA alone.It is attached to a microphone and a sound is delivered, and the output is measured and graphed.

Copyright by Linda M. Thibodeau 2005

next the fm receiver is attached and the ha fm system is evaluated
Next the FM Receiver is attached and the HA/FM system is evaluated.

Copyright by Linda M. Thibodeau 2005

slide60

The output curves are compared to verify that Curve #2 (FM + HA) shows that the FM signal will be higher than the Hearing Aid alone signal.

Copyright by Linda M. Thibodeau 2005

b real ear procedures
B. Real Ear Procedures

Settings can also be verified by placing a small tube microphone in the child’s ear canal and measuring the sound level while

1) first wearing the HA alone, then

2) while wearing the HA + FM system

2)

1)

Copyright by Linda M. Thibodeau 2005

c behavioral testing with fm systems
C. Behavioral Testing with FM Systems
  • Threshold Testing typically not recommended due to lack of significant information
  • Speech Recognition Testing is more meaningful
    • Without FM System
    • With FM System, with examiner wearing FM transmitter
  • Test each arrangement in Quiet and in Background Noise if time permits

Copyright by Linda M. Thibodeau 2005

test arrangement
Test Arrangement

Examiner Side of Test Booth Student inside Test Booth

Copyright by Linda M. Thibodeau 2005

behavioral fm verification case illustration
Behavioral FM VerificationCase Illustration

Third Grader who resisted wearing FM system.

Testing done to show him benefits.

  • Hearing Aid Alone
    • Quiet 90%
    • In typical classroom noise 60%
  • Hearing Aid with FM
    • In typical classroom noise 90%
    • Quiet 100%

With the FM System, the speech recognition score improved from 60% in noise to 90%!

Copyright by Linda M. Thibodeau 2005

slide65
We’re now at the fourth, and final section

of the lecture….

Let’s consider some ABC’s of using FM Systems in the Classroom!

Copyright by Linda M. Thibodeau 2005

4 use of fm systems
4. Use of FM Systems

A. Microphone Technique

B. Care and Use

C. Settings for Various Teaching Arrangements

D. Troubleshooting

E. Common Problems

F. Manufacturers

Copyright by Linda M. Thibodeau 2005

a mic technique
A. Mic Technique
  • 1. proper distance 6-8 in from mouth

(unless using boom mic, then 2 in)

  • 2. don't stand near noise
  • 3. turn off when leaving the classroom
  • 4. antennae must hang free, not wrapped around transmitter

Copyright by Linda M. Thibodeau 2005

b care use
B. Care & Use
  • 1. clean units with damp cloth
  • 2. if put in prolonged storage - need even temperature
  • 3. annual electroacoustic checks
  • 4. daily listening checks
  • 5. keep in chargers when not in use

Copyright by Linda M. Thibodeau 2005

c settings for various teaching arrangements
C. Settings for Various Teaching Arrangements

Copyright by Linda M. Thibodeau 2005

settings on fm receivers
Settings on FM Receivers

FM Receivers usually have switches that can be set to send certain signals to the listener:

FM Only-Sends only the teacher’s voice

Environmental (ENV) Only-Sends

only the voices picked up by the

microphone on the FM Receiver

FM+ENV-Sends the teacher’s voice and the environmental sounds around the student, ideally the teacher’s voice is about 10 dB more intense than the ENV signal

Copyright by Linda M. Thibodeau 2005

1 teacher lecture
1) Teacher lecture
  • Set Receiver to pick up FM Only Signal

I think they like

my tux!

Copyright by Linda M. Thibodeau 2005

2 class discussion led by the teacher
2) Class discussion led by the teacher
  • Set Receiver to pickup FM + Environmental (ENV) Signals

I’m not sure

they’re listening.

How To Select

Hearing Aids....

Copyright by Linda M. Thibodeau 2005

3 independent work at desk
3) Independent work at desk
  • Set Receiver to pickup up ENV Signals

I’d rather be

shopping!

Copyright by Linda M. Thibodeau 2005

4 group work

I’d rather be

fishing.

4) Group work
  • Set Receiver to pickup ENV Signals

Copyright by Linda M. Thibodeau 2005

d troubleshooting
D. Troubleshooting -

Works best when two people check each component separately and the add components progressively according to the following steps:

Copyright by Linda M. Thibodeau 2005

slide76
1. check FM receiver in microphone mode (as a body aid)
  • 2. check FM receiver & transmitter in FM mode
  • 3. check FM receiver & transmitter in FM & Microphone mode

Copyright by Linda M. Thibodeau 2005

slide77
4. check FM Receiver & transmitter & personal aid (boot with loop silhouette)
  • 5. check personal aid alone.
  • 6. annually check each component, daily check entire system (#4)

Copyright by Linda M. Thibodeau 2005

e common problems
E. Common problems
  • 1. setting volume controls - must be determined by audiologist
  • 2. matching oscillators between transmitter and receiver
  • 3. setting the mic switch
  • 4. neckloops often noisy & inconsistent signal

Copyright by Linda M. Thibodeau 2005

slide79
5. changes in frequency response re: to hearing aid alone when using direct input or neckloop
  • 6. access to audiologist who can monitor
  • 7. dead batteries
  • 8. broken cords

Copyright by Linda M. Thibodeau 2005

f manufacturers
F. Manufacturers

Web pages are VERY helpful, but do not hesitate to contact manufacturer to ask questions:

1. Phonic Ear

www.phonicear.com

2. Telex

www.telex.com

3. Comtek

www.comtek.com

4. AVR Sonovation

www.avrsono.com

5. Phonak

www.phonak.com

Copyright by Linda M. Thibodeau 2005

summary
SUMMARY
  • The SNR can be significantly improved by using an FM system.
  • Because there are so many options, the audiologist is responsible for selection and fitting of FM systems and the necessary orientation and counseling.
  • Any connection of hearing aid or cochlear implant with an FM system should be tested in controlled conditions to determine benefit.
  • FM systems must be monitored on a regular basis by trained personnel under an audiologist’s supervision.

Copyright by Linda M. Thibodeau 2005

last minute advice regarding using fm systems
Last Minute Advice regarding using FM Systems….

If you have a lot of tension and you get a headache, do what it says on the

aspirin bottle: "Take two aspirin"

and

"Keep away from children."

Copyright by Linda M. Thibodeau 2005

references
REFERENCES
  • American Speech, Language, and Hearing Association (2005). Acoustics in Educational Settings: Technical Report, ASHA Supplement 25, In Press.
  • American Speech, Language, and Hearing Association (1999). Guidelines for Fitting and Monitoring FM Systems. ASHA Desk Reference, 2, 151-171.
  • Finitzo-Hieber, T., & Tillman, T.W. (1978). Room acoustics effects on monosyllabic word discrimination ability for normal and hearing-impaired children. Journal of Speech and Hearing Research, 21, 440-458.

Copyright by Linda M. Thibodeau 2005

acknowledgements
Acknowledgements

Erin Schafer, M.S.

University of Texas at Dallas

Paul Dybala, M.S.

University of Texas at Dallas

Gary Overson, M.A.

University of Texas at Dallas

Jack Scott, M.A.

University of Texas at Dallas

Marcia Crouch, M.S.

Plano Regional Program for the Deaf

Amy Popp, M.S.

Cochlear Corporation

Sallie Frye, M.S.

Frye Electronics

Helmut Ermann

Phonak Hearing Aids

Copyright by Linda M. Thibodeau 2005