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Hearing Resources

Regular (standard) FM or Dynamic FM 

FM has come a long ways since the early 80's when most of the equipment was larger body belt worn transmitters and receivers operating on the 72-75 MHz band set aside by the FCC as a shared band for Assistive Listening FM Devices and an assortment of commercial and personal walkie-talkies along with truck and taxi dispatch.  This was okay at the time as there was very little use of the radio band by other users at the time.  As time passed and wireless communication became more common the band being used became crowded with these other users.  Now this lower band is too crowed in most major metropolitan areas and the higher grade assistive listening FM equipment is moving to the higher 216-217 MHz band the FCC has set aside for our use exclusively. 

What is a wireless communication system (FM)?

Wireless communication technology is very common today for a multitude of applications and situations all over the world, whenever communication is in the focus of interest. Other examples of the use of wireless communication technology are:

• Cable-free telephones
• Walky-talkies
• Baby monitoring systems

An wireless communication system (FM system) for hearing instrument users works on the same principle. It consists of a transmitter, which picks up the voice from the speaker and sends it via radio waves, wirelessly, directly to the tiny radio (FM) receiver, which is connected to the personal hearing instrument.

Standard FM Features

Today we have extremely small FM receivers, some that integrate directly into a Behind-the-Ear (BTE)hearing aid or plug right into the bottom of the BTE hearing aid.  The FM transmitters, while not as small, are much more functional now days with switchable array digital microphone technology.

• Full frequency flexibility, with direct frequency synchronization through the transmitter and automatic frequency synchronization through the WallPilot

Dynamic FM Features

Highlights:

• All Dynamic FM products have the full feature set of Phonak's current multi-frequency FM systems.  This guarantees full backwards compatibility.

  Smart Noise Blocker: a clever way to suppress channel noise in the receiver and to improve sound quality when a person is not speaking.

• Dynamic Speech Extractor: A clever algorithm that improves the signal-to-noise ratio (SNR) in noisy conditions by up to 15 dB over traditional FM systems.  Improves speech scores by up to more than 80 percentage points. 

  • Working principle:  the transmitter measures continuously the ambient noise level, if the noise is above a certain level, a sub audio wireless DataLink from transmitter to receivers tells the to increase gain.  During validation, 100% of users preferred this in noisy situations over classic FM.

• Voice Activity Detector in the transmitter opens the receivers only when when someone is talking.

• Easy Adjustment of FM Advantage provides a convenient way to adjust the FM output level t the listener's personal preference.

• AutoConnect: A feature of the MLxi universal receiver automatically measures the impedance of the audio input of the hearing aid and sets its own output impedance accordingly.  This ensures that tolerances in specifications of hearing aids of different brands are corrected, that FM levels are always right on target, and that verification and programming of receivers is no longer necessary.

Now Dynamic FM features in many of the integrated products. Digital Dynamic FM (FMi) technology incorporates a wide range of features at includes the automatic monitoring of  background noise along with some suppression of this noise plus the automatic control of the hearing aid microphone sensitivity (sensitivity is reduced which reduces background noise at the person's hearing aid microphone) while the wireless microphone is being talked into and when the  wearer or source at the wireless microphone is quiet the volume of the person's hearing aid microphone is returned to normal.  In addition several other features are being modified automatically in the background to improve speech clarity.  In reality Dynamic FM is proving to be the greatest step forward in FM technology since the reduction in FM receiver size from a box the size of a package of cigarettes to a device the size of a dime and from a weight of 8-10 ounces to that of a nickel. 

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