Number Color Freq (MHz)

#1 Red/Gray  ___________

#2 Brown/Gray  ___________

etc.....#40

10 Wide Band

#1 Red  ___________

#2 Brown  ___________

etc....#10

Five types of FM systems are:

Soundfield: speakers in a room for a group of people to listen
Basic: button earphone to deliver sound to child
Personal: sound coupled to the personal HA via direct input, silhouette, or neckloop.
Earlevel: FM receiver is in BTE case which also works as a HA
Boot: FM receiver is in boot that snaps onto BTE HA

Basic FM Signal - Transductions = acoustic > electric> FM frequency> electric > acoustic

III. PARTS OF THE FM SYSTEM

A. Transmitter

Microphone Options:

___________
Directional
Boom
Conference
___________

Transmitting Frequency Options:

___________ frequency
___________ frequency

Signal Inputs:

Audio in jack
Microphone jack

Controls:

Low Battery Light
___________
Automatic Gain Control

B. FM Receiver Options

Microphones:

___________ Omnidirectional
Dual Omnidirectional
Dual ___________
Behind the Ear

Frequencies:

Single Channel
Dual Channel

Internal/External

Input/Output Jacks:

___________
Audio in jack
Audio out jack

Controls:

FM, FM+ENV, ENV
___________, Tone FM Ratio, R/L Ratio, Gain
Volume of FM Signal
Volume of Env Signal
NO FM Light
___________ Light

Coupling Options:

Headphone
___________
Bone Oscillator
___________ Earphones
Behind the Ear
Personal Hearing Aid via:

___________
Neckloop
___________
FM Boot Receiver

C. Battery Options

Batteries:

Removable  ___________ Battery Pack
Removable  ___________
Removable  ___________

Chargers:

Case
Modular
Wall

D. IDEALIZED FM SYSTEM

Ideal Transmitter

___________ Transmitting channels
Audio input with Talkover
___________ Microphone
Low Battery Lights
No FM Lights

Ideal Receiver

Dual Channel  ___________
Input/Output jacks
Options for FM, FM+ENV, ENV
Direct-input Coupling or Boot Receiver (?)
Low Battery Lights
No FM Lights

Ideal Battery

Operate on Nicad OR Alkaline
Modular charger with auto off

E. FACTORS INFLUENCING CHOICE OF FM SYSTEM

Age of the Child- The older the child the more likely they’ll want to use the neckloop or direct-input. Select hearing aids that will be capable of working in neckloop or direct-input arrangements.

Type of Hearing Aid- Fit with direct-input if all signal options are available (FM only, FM+ENV, and ENV only). Do not fit with direct-input or neckloop if "FM only" is not available.

Degree of Hearing Loss- Children with mild losses may use headphones or soundfield amplification. Children with more severe losses may use personal aids, button or ear level receivers.

Availability of Support Personnel- Use of personal FM involves more equipment to check and therefore may require additional personnel. Also important that personal aid is maintained by the family.

Instructional Arrangement- May not be able to use a personal FM arrangement if FM+ENV is not available and the child is in a class where passing of the FM mic is not feasible.

Financial Resources- The more options that are included, the greater the cost (eg. Comtek systems have few controls for tone, output, etc. and are least expensive.)

Client Preference- This is more important as the child gets older. Preference may take priority over acoustics (i.e. may go with neckloop rather than direct-input).

F. Comparison Shopping

??? Basic vs. Personal FM ???

The personal FM system is most desirable because.....

Potential for more consistent   ___________ characteristics exist

Child can keep personal aid on all day

Adds to  ___________ of personal aid

??? Direct Input vs. Neckloop ???

Although in both direct-input and neckloop arrangements.......

Frequency range is possibly altered & FM receiver  ___________ are not
linear,

Direct-input is electroacoustically most desirable because.....

Low frequencies are generally reduced with  ___________.

Signal strength is variable with head orientation re: neckloop.

Equivalent input noise is higher with neckloop/silhouette than with DI

IV. EVALUATION OF FM SYSTEMS

A. Auditory-Visual Checks

___________
FM receiver as body aid (set to ENV only)
FM receiver as a an FM system; (HA coupled to FM and receiver set to FM only)

The individual steps may be done monthly and only the final step done daily. If there’s a problem, then the individual steps should be done.

B. Electroacoustic Measurements-

There are two procedures, depending on whether there is only a single unit or several units within a school. For the single unit, the steps for the aud/vis inspection are followed.  ___________ test procedures for hearing aids are used. The FM microphone is placed in the test box while the output of the FM receiver is connected to the2cc coupler. Results may also be obtained at user settings. Because there are no standards for the evaluation of FM systems, the results may only be compared to baseline results obtained with the same procedures. For situations where multiple units are used, the variability across units should be assessed. A control unit, which is working properly, must be used to provide constant components while the component of interest is varied.

The following components are evaluated using ANSI procedures while holding the remaining components constant:

FM Receiver as a body aid, FM lapel microphones, FM receiver in FM mode, and neckloops.

C. ___________ Eval-

In order to account for the greater input to the FM microphone relative to that at the HA microphone, use a higher input for the FM system than for HA only. Hawkins recommends using 80dB SPL for the FM system and using 60 dB SPL for the HA only (Pure tone Stimuli).

In both cases the, microphones are positioned at the top of the ear near the reference microphone. Assuming that the HA has appropriate gain, Hawkins suggests matching the output at 1000 Hz achieved with the HA only (60 dB SPL input) to that obtained with the FM system (or HA + FM) (80 dB SPL input) by rotating the volume on the FM receiver.

D. ___________ Eval-

First aided thresholds may be determined with their personal hearing aid in typical way. Then the FM mic is placed in the calibrated location in the soundbooth and the client wears the FM in the room with the clinician.

In this arrangement, it is expected that the HA alone condition will result in lower thresholds because the gain is higher than with the FM system because of the different input levels to the two systems. Remember with the FM system, the mic is closer to mouth and the input is higher so we don’t need as much gain. The difference in thresholds is approximately 20 dB.

Problems with  ___________ testing- It’s hard to replicate the real-world situation. Some try to do this by placing the FM mic 6 inches from the speaker but there are two problems.......

1) There is too much variability in vertical and horizontal dimensions which may result in variability in the signal levels arriving at the FM mic.

2) In addition, the FM systems may operate differently for low level signals than for higher level ones like speech because of compression.

E. Results of Electroacoustic and Behavioral Evaluations

1. SPEECH RECOGNITION FOR DIFFERENT  ___________ MICROPHONES (Mayfield, 1992)

Percent Correct on SPIN Sentences by Normal Hearing Adults with Different FM Microphones

Button Earphone BTE

Omnidirectional  ___________
Directional  ___________
Boom ___________

CONCLUSION:
The  ___________ microphone resulted in significantly better speech recognition for normal-hearing listeners than the other microphones except for the directional microphone with a button earphone.

2. Electroacoustic   ___________ in Direct-input Arrangements (Thibodeau, 1990)

2 FM systems were evaluated with 20 Direct-input Hearing Aids

Conclusions:
FM System #1 resulted in an average  ___________ in the frequency range for Aid+FM re: Aid alone while FM System #2 generally resulted in an ___________ (Figure 2) Aids with similar gain may not have the same output when connected via direct input to an FM System (Figure 5)

3. Electroacoustic variations in   ___________ Arrangements (Thibodeau, McCaffrey, Abrahamson, 1988)

2 FM Systems were evaluated with 12 Hearing Aids via  ___________ arrangements

CONCLUSIONS:
There was an increase in FOG for one FM system while there was a slight decrease for the other in the Aid+FM re: Aid alone conditions (Figure 1a) There was an increase in EIN for both FM systems when used in the neckloop arrangement (Figure 1b) The degree to which the low-frequency gain was reduced could be predicted by comparing the output of the HA alone in microphone and T-coil modes (Figure 2). The variations in signal strength with head movement were greater for FM System #2 than for #1 (Figure 4).

4. Electroacoustic Variations across a group of  ___________ (Thibodeau & Saucedo, 1990)

Evaluated 30  ___________ of the same manufacturer across 3 different schools and found variations primarily in frequency response, volume control linearity, and EIN.

V. SOUND FIELD FM SYSTEMS

A. Rationale - Improving  ___________ ratio and keeping an even sound pressure level around the room.

B. Target Populations - Normal hearing children with attention deficit disorders, learning disabled , children with mild or fluctuating loss (preschoolers w/ME infections or Down’s children).

C. Components

Microphone--- ___________

Base Receiver--- ___________----Speakers

D. Studies showing benefit

-MARRS-Mainstreamed Amplification Resource Room Study (Ohio, 1981) - Kindergarten class - mild losses w/ NUCHPS showed significant improvement w/ FM.

-MARRS- compared SF amplification to Resource Room (RR) placement in 4th, 5th, and 6th grades w/ kids w/ mild hearing losses. There was a control group in regular class.

The SF and RR kids showed improvement over control group. SF is more natural intervention (helps all kids); doesn’t make HI kid as self-conscious. Also SF is less expensive than RR.

-Ohio-Putnam County did MARC-Mainstreamed Amplified RegularClassroom - Kindergarten through 3rd grade in regular classroom for normal hearing children. Some used SF, some didn’t.

With SF, significant gain in academics over control classes. Number of Special Education kids reduced from 68 to 42 over 5 yrs.

E. Advantages and Disadvantages

SF ADV-

1. Cost- 1 system is less expensive than SP Ed for 1 child

2.  ___________ all children

3. No stigma

4. Lower  ___________ for children

5.  ___________ acceptance-save their voice

6. Teaches good communication skills-use mic one at a time, etc.

SF DISADV-

1. Doesn’t work well in noisy or  ___________ room- only 30 dB gain because of feedback

2. One signal level may not be   ___________ for all.

3. Sound via  ___________ arrangement is not 100% uniform unless there are a large number of speakers.