FM Systems…when a hearing instrument is just not enough

Or should I call this post “Let’s get rid of the Freakin Noise 2: FM Systems”.

I talked about Directional Microphones and how they can reduce the noise but about 4-5 dB.  This technology is great for folks that have up to a moderate (50 dB HL) hearing loss.

But for people with moderate-severe (60 dB HL) losses or greater, you need more than directional microphones on your hearing aid.

Here’s why.  Many times we find ourselves in places where the signal to noise ratio (SNR) is 0 dB.  This means that the noise around you is the same loudness and the person you want to listen to.  Think about a restaurant or bar with all sorts of people blabbing away.  They are the same loudness as your spouse or buddy in front of you.

When you have a moderate-severe hearing loss, you need a SNR of 7 dB or greater to understand.  So if a directional microphone gives you a 4 dB improvement, that’s still not enough.

An FM system gives you a 15-25 dB improvement.  Now you can converse much easier in this noisy environment.

Here’s a link to a section on the Phonak Website that explains how FM systems work.  But the key to getting the most out of an FM System is knowing how and where to use them.  Here are the places that I personally use mine:

  1. Car
  2. Restaurant
  3. Coffee Shop (Tim Hortons…mmmmm)
  4. Meetings
  5. Skiing Lessons
  6. Kayak Lessons
  7. Parties
  8. Bars
  9. Listening to iPod
  10. GPS in car
  11. Bass Guitar Practicing
  12. Live shows
  13. Tour guides
  14. and more
Next blog entries will highlight how to use an FM system in this situations.

That’s Why I Like the Blues

Playing and listening to music can be a challenge to people with significant hearing loss.  For some people, the sound quality is poor.  Others find music noisy and confusing.  They can’t make heads or tails out of things.  It all sounds really bad.

Yet for other people like myself, music is quite enjoyable.  Not only that, there are some people with significant hearing loss like myself who even play an instrument in a band.

So why the huge differences?  Why do some people with hearing aids and cochlear implants find music to be unpleasant, while others love it?  This is a huge topic that is currently being researched at Universities as we speak.  Over time I will touch on many of the reasons that I am aware of, including the settings of the hearing instrument, the additional equipment you may use (e.g. FM systems), previous experience with music, musical training, and even the type of music you listen to.

One way to enjoy music is to become familiar with a certain genre.  Lets take the Blues for example.  What I like about the blues is that it has a certain predictable pattern we generally call the “12 Bar Blues”.  Basically it uses the following pattern:


In any scale there are 7 notes we use.  The most familiar would be the C scale.  So in the key of C, the notes and their corresponding chords would be would be:

Numeric Note Chord
ii D Dmin
iii E Emin
vi A Amin
vii B Bdim

So if I was playing the blues in the key of C I would play 4 bars of C, then 2 bars of F, 2 bars of C again, one bar of G, one bar of F, then 2 bars of C again.  I can figure this out for any key; all I need to know is what key are we playing in.  So if I am having a jam session with the band mates, I just ask for the root key.

By becoming familiar with the music, my brain seems to make more sense out of it.  It seems less confusing and less anarchic.

Our brains do the same thing when we are talking to one another.  When we are given a familiar phrase in a familiar language, we can predict what is coming next.  For example if some says ‘Please pass the salt and ______”, we pretty much know that the last word is going to be pepper.  But if someone says, “We were talking about______”, the last word could be anything.

Music is also like a language.  So if we stick to genres that have predictable patterns and cycles, it becomes easier to hear, enjoy, and even play.

And that’s why I like the Blues.

Let’s get rid of some of that freakin’ noise 1: Directional Microphones

As promised, I am going to continue the discussion on getting rid of noise.  In this post, I want to touch on the topic of directional microphones that can be found on hearing aids and cochlear implants.

But before doing so, lets summarize again the two main problems you have with a sensorineural hearing loss.

  1. Loss of Audibility
  2. Loss of Clarity

Loss of audibility simply means that you can’t hear certain sounds well. They are too soft.  So we need to make them louder in order to hear them again.  Interestingly, the loud sounds may still sound OK.  Also, the level in which sounds become uncomfortable for you may only be raised a little bit.

Fortunately, today’s modern digital hearing aids do a really good job at making things audible again.  They amplify soft sounds more than loud and amplify some pitches more than others (based on your hearing loss).  Cochlear implants also do a great job of bringing sound back to people who can barely hear at all.

Loss of clarity especially in noise means that when there are other noises present, you have a hard time communicating.  Amazingly, people with normal hearing can still communicate when the signal to noise ratio (SNR) is 0.  In other words, if the person talking to you is 65 dB and the other people around you are also 65 dB (think a restaurant), that is a 0 dB SNR.  Normal hearing people can still understand in the situation (makes me sooooo freakin’ jealous).

We folks with hearing loss can’t do that.  We need a higher SNR and the more hearing loss you have, the higher the SNR you need.

Directional microphones on the hearing aid (and cochlear implant) are one way to get rid of noise that actually works.  There are some great sites that explain how they work.  This link has a nice article that explains directional mics.  Also check out this link that shows what a modern directional mic system can do.

In a nutshell, directional microphones work by picking up sound in front of you more than behind you.  The assumption is that the person talking to you is typically facing you.  They get rid of about 4 to 5 dB of noise.  This amount of improvement is sufficient for adults with mild to moderate degrees of hearing loss.  But once we get to a moderate-severe degree of hearing loss (around 60 dB HL), the directional microphone won’t be enough.

So who should get a directional microphone? Well, every person with a hearing loss, regardless of degree of loss.  Folks with milder losses will need it in a restaurant, shopping mall, store etc.  People with moderate losses or greater may even need it in the home if the fridge noise, dishwasher, or TV is on.

But people with moderate-severe, severe, and profound hearing loss must have an FM system if they plan on stepping out of the house.

Time for one more rant:

If you as an audiologist are not picking hearing aids with at least a directional microphone, you are only doing half of your job.  All you have done is addressed the audibility problem, and are doing nothing about hearing in noise.  If you don’t plan on adding a directional mic, I hope you have picked a hearing aid that can use an FM system (see earlier rant).

If you as a hearing aid wearer insist on only wearing tiny “dirty little secret” hearing aids that have no room for a directional microphone or no capability of using an FM system, you are doing yourself a huge disservice. Good news however, is that the hearing aids with directional mic and FM capability, while not exactly the “tiniest” ones out there, are still quite small.

Challenges of hearing loss.

Many people think that a hearing loss simply means that we need to make things louder.  It is actually more complicated than that.  Not only do we need to make sounds louder, but we also need to make sounds clearer.

Most people have what is called a sensorineural hearing loss.  This usually means that the tiny hair cells of the inner ear, or cochlea, have been damaged.  This link here has an excellent picture of both healthy and damaged hair cells of the cochlea.

I have added the picture below.

The cochlea has 2 types of hair cells; inner hair cells (IHC) and outer hair cells (OHC).  The function of the outer hair cells (OHC) is actually to make soft sounds louder.  These are the first to get damaged.  If this were the only damage you have in your cochlea then amplifying only the soft sounds is all you need in order to hear better.

The second type are called the inner hair cells (IHC).  Inner hair cells actually trigger the nerves that send the message to your brain.  As you can see from the picture, the inner hair cells can also be damaged.  The greater your degree of hearing loss. the more damage you also have to the inner hair cells.

Inner hair cell damage results in pieces of sound missing altogether.  It makes speech unclear.  It makes it harder to pick out speech from background noise. For musicians, it makes it harder to recognize the correct pitch of a note.

Today’s modern digital hearing aids that carefully amplify soft sounds more than loud sounds and amplify certain pitches more than others, do a very good job of replacing the function of the outer hair cells.  But as the hearing loss gets greater and you have more inner hair cell damage, we need to clean up the signal even more.

In my next blog entry, I will explain how directional microphones and remote wireless FM systems help to clean up the sound and make hearing aids work even better.