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.
- Loss of Audibility
- 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.