HIS 140 - Technologies Which Support HI Effectiveness

Technologies which support HI effectiveness

There are two causes for sound wave travel degradation.

First, the weaker sound is more easily masked by background noise.

Second, the initial sound may begin to be deflected and begin to reverberate.


Critical distance

Is defined as the distance from the source beyond which the level of the reverberant sound exceeds the level of the direct sound.


Critical distance is what must be determined for the patient/client’s communication requirements and the performance of the hearing instruments you are recommending.


There are four basic remote sensing and transmitting hearing systems which may support HI effectiveness.

They are:

1. Induction loop systems

2. FM systems

3. Infra-red systems

4. Bluetooth systems


Induction Loop Systems

A transmitter creates a magnetic field through a wire loop. This wire loop can be a large as an auditorium.


The listener must be within the magnetic field of the loop transmitter and possess/wear a device which is capable of transducing the magnetic field information into acoustic sound.


Many hearing instruments have telecoils which are magnetic field receivers. They may be a standard HI feature or an ordered option.


Older telephones emitted a magnetic field to activate the telecoil of hearing instruments. Most telephones today must be purchased as a “hearing aid compatible” telephone to ensure that the phone will activate the telecoil receiver.


As a hearing instrument professional, it is important to make certain that the frequencies transduced by the hearing instrument receiver are appropriate for the patient/client’s hearing loss.


FM—Radio frequency systems

These devices transmit on radio frequencies dedicated for communication purposes. They have the same success and limitations of radio transmissions we have enjoyed over the years.


Their dedicated transmission distance is small enough that the same transmission frequencies may be used in classrooms of large schools.


For individual FM transmitters, a body worn microphone is used by the speaking individual. Please review Dillon page 65 for some practical tips on wearing an FM transmitter.


FM receivers may be integrated into hearing instruments or, ordered with an FM boot option attached to the HI. Again, the fitting professional must make certain that the frequencies transduced by the FM boot/coupling are appropriate for the patient/client’s hearing loss.


Infra-red hearing systems

These are ultra-high frequency radio waves. Their frequencies are so high, that their radiation is perceived by humans as a red light.


Since these frequencies operate at almost the same frequency as light waves, its effective distance can be reduced by bright sunlight.


Due to its characteristics of light, this system will, of course, require a “line-of-sight”.

It will not emit through walls, doors, etc.

due to its characteristics of light.

A system comparison chart detailing the relative advantages of these three systems may be found in Dillon page #71.


Bluetooth Hearing Systems

Are very popular connections between cell phones and “streamers”

Streamers are devices which transform and transmit the Bluetooth signal to the hearing instrument.


Again, the hearing instrument provider must make certain that the transmitted frequency information is sufficient for the patient/client’s hearing loss.


Other assistive devices

There are two primary categories of other devices which may assist the deaf and hearing impaired. They are:

1. Devices which improve speech intelligibility.

2. Devices to detect environmental sounds


We will cover assistive listening devices (ALD’s) in a future

presentation.

Technology

HIS 140 - Technologies Which Support HI Effectiveness