Balancing FM Systems. BATOD March 2013

Colin PeakeEducational Audiologist

South of England Cochlear Implant Centre

Two Questions ……

• Why Use Personal FM Systems?

• What is the purpose of balancing FM Systems?

Balancing FM systems. BATOD March '13

Balancing FM systems. BATOD March '13

Why Use Personal FM Systems

FM AUDITORY TRAINING SYSTEMS.

Characteristics, Selection, and Use.

Ross, 1991

Why Use Personal FM Systems?

The ability to discriminate individual phonemes, to hear words/sound differences, is defined as intelligibility, as distinguished from audibility, which is the ability to detect the presence of speech. If because of hearing loss, poor classroom acoustics, and/or poor attending skills, a child cannot discriminate wave from raise, for example, he or she will not learn appropriate semantic distinctions unless deliberate intervention occurs.

•Carol Flexer in, FM AUDITORY TRAINING SYSTEMS. Characteristics, Selection, and Use. Ross, 1991,

Balancing FM systems. BATOD March '13

Balancing FM systems. BATOD March '13

Why Use Personal FM Systems?

“The purpose of using technology is to promote the child’s right to hear and to benefit from educational instruction.”

Carol Flexer in, FM AUDITORY TRAINING SYSTEMS. Characteristics, Selection, and Use. Ross, 1991,

Balancing FM systems. BATOD March '13

Kimberly

Balancing FM systems. BATOD March '13

What is the purpose of balancing FM Systems?

• To ensure that the level and quality of sound a child hears through the FM Systems microphone matches what he hears through the hearing instrument’s microphone.

Balancing FM systems. BATOD March '13

Importance of Level• Too High

– Serious risk of distortion

– Danger of Compression

• Too Low

– Makes little difference to the child

– Denied the right to access and benefit from instruction

– Waste of resource

– Disenchantment

Balancing FM systems. BATOD March '13

Importance of Quality

• Frequency response curves

Balancing FM systems. BATOD March '13

Frequency response curves for Medel Opus 2 (curve #1 @ 60 dB and with CA Digisystem (curve#2 @ 65 dB

When Should Balancing be Done

• At initial fitting

• Change of hearing instrument

• Change of FM system

• Disturbance of controls

Balancing FM systems. BATOD March '13

Balancing FM systems. BATOD March '13

Good Practice Fitting Procedure Listening check of speech processor and FM

system where possible, adjust settings.

An objective test-box method for setting up levels (see Quality Standards and Good Practice Guidelines)

Validate the settings with a speech test (eg McCormick)

or

Validate the settings with a speech in noise test

But, what if a child can’t do a speech test?• May have poor discrimination years after

implantation

• May not co-operate due to

– tiredness

– immaturity

– language difficulties

– behavioural difficulties

Balancing FM systems. BATOD March '13

• Callum

Balancing FM systems. BATOD March '13

Other Inputs Applied to FM TransmittersOutput from

– Television.

– CD player, other audio devices

– Computer/Whiteboard

– Soundfield device.

Balancing FM systems. BATOD March '13

Other Inputs Applied to FM TransmittersTelevision, CD player, other audio devices,

computer/ whiteboard.

All should be used with caution – only on children who can report accurately.

Soundfield systems .

Used in the context of learning so must be balanced.

Balancing FM systems. BATOD March '13

Balancing Soundfield Systems

• Obtain FR curve for hearing instrument

• Obtain FR curve for FM system and adjust volume so curves match

• Set FM transmitter to re-broadcast, place soundfield emitter in the test box – lid open.

• Obtain frequency response curve and adjust output of soundfield system so curves match.

Balancing FM systems. BATOD March '13

Demonstration

• Re-broadcasting.avi

Balancing FM systems. BATOD March '13

Any further enquiries to:

c.peake@soton.ac.uk

Balancing FM systems. BATOD March '13