Several hearing aid manufacturers have a tab on their fitting software that allows the hearing health care professional to adjust the parameters of the “music program” for various music genres. For example, one manufacturer specifies less gain for rock and roll and more gain for jazz and blues. The rationale is that they want to obtain the same output regardless of the type of music- a louder form of music needs less gain in order to obtain a desired output.
This assumes that all other aspects of the hearing aid have been optimized to handle the inherently louder inputs of music, and this is rarely the case. Since the advent of digital hearing aids we have been playing catch-up to the time of the late 1980s. The analog K-AMP of 1988 had it all figured out and could transduce music with virtually no distortion.
With the advent of digital hearing aids and the necessary analog to digital (A/D) converter we have taken a major step backwards. And the specification of music genre specific settings in the hearing aid fitting software is just the latest incarnation of this “catch-up game”. Very loud music will typically only have a few decibels of gain associated with it and soft jazz/blues may have slightly more.
But we really don’t need to have the various music genre offsets or corrections in the first place. More intense inputs will generate less gain and will simply operate within different ranges of the input-output function of the compression circuitry.
Returning to the issue of the analog-to-digital converter, also known as the weak link in modern digital hearing aids, if this is overdriven by intense inputs of music, the ensuing distortion will be uncorrectable. Software that sets lower gains to an already highly distorted signal will really not be much better than specifying higher gains to a highly distorted signal.
The same can be said for altering the shape of the frequency response. This is more of an issue related to the configuration of the audiogram as well as its severity (with a more narrow band response specified for steeper sloped audiograms). This has been well studied and is related to the hearing loss, and not the input. Differing genres of input music should have no effect of the frequency response.
The way to optimize a hearing aid for music has been known for years (I even wrote an article about this which was published in Trends in Amplification in 2004). I admit to being frustrated by the hearing aid manufacturing industry’s rather minimal attempts to build a better hearing aid for music. Increasing or decreasing gain in certain frequency regions, or altering the frequency response are, feeble attempts to return to the K-AMP fidelity of 1988.
And having a glossy ad showing a musician smiling while playing their music does not mean that the hearing aid technology can handle music- it’s just a glossy ad.
Forget about music specific genres. Forget about altering the bandwidth of the hearing aid for music. And forget about wasting money on glossy marketing ads and posters.
If the louder components of music distort the analog-to-digital converter which is before the software, nothing “programmed” later on in the hearing aid circuit can bring back the fidelity of the music.
So, what are some things that can be done? To be more specific, what can be done before the signal reaches the analog-to-digital converter to ensure that it is not over driven by intense inputs?
One can reduce the input to the hearing aid- an easy recommendation for our hearing aid clients. When listening to music at home or in the car, turn down the volume of the stereo or car radio, and if necessary turn up the volume of the hearing aid. The opposite will not work. There will be poor fidelity if the home stereo is turned up and the hearing aid is turned down. The input must be minimized to the extent that it can.
Ready for “low-tech”? Try this experiment. Place several layers of scotch tape over the hearing aid microphone(s). You may need to experiment with one, two, or three layers to see which is the best, but this idea works because it reduces the sensitivity of the hearing aid microphone to the point that what is delivered to the analog-to-digital converter is 10-12 dB less intense. There will be significantly less distortion.
There are many other techniques- see previous blogs- but let’s not waste our time fiddling with software programming adjustments that are designed primarily as marketing techniques to sell hearing aids.
