Tech Forum

An advanced digital hearing aid employs digital signal processing for all sorts of tricks. For one, the individual's hearing loss spectrum can be compensated without large analog filters. But DSP also allows for the removal of noise, constant tones (real ones), feedback, etc. and for the adjustment of gain and directionality. I think I've read that certain types of tinnitus can be reduced by sufficient levels of band-limited noise. Apparently, the brain interprets zero noise as a tone. Such noise generation is easy with DSP.

Analog amplifiers amplify all audio frequencies equally, simply making everything louder. Digital hearing aids process the digitized sound with a tiny microprocessor before converting the digital signals back to analog for your ear. Therefore, they can be programmed to amplify different frequencies by different amounts.

Most senior citizens with hearing loss have more loss of high frequencies than low.  Unfortunately, it's the high frequencies that convey most of the meaning of speech. Your audiologist will probably program your digital hearing aid to amplify high frequencies more than low, resulting in much better speech understanding than simply making everything louder.

It usually takes two or three trips to the audiologist to get your hearing aid programmed just right for you. That personal attention is built into the price of the digital hearing aid, which is why they're so expensive. Believe me, they're worth the extra cost!

A digital hearing aid still has an analog microphone, mic pre-amp, audio power amp and speaker (earpiece). It's what's in the middle that's digital: a programmable digital signal processor. The DSP takes the mic input and converts it to bits of data (digital). The DSP can analyze the data and make adjustments depending on the programming. For example, if you have a hearing loss at 2,000 Hz the audiologist can program a boost in your hearing aid at 2,000 Hz. If after some time your hearing becomes diminished overall, the audiologist can program a general boost of all the frequencies if needed. The DSP can make smart decisions to automatically reduce or eliminate feedback and background noise. The latter can help you understand conversations in a noisy room. The DSP can automatically adjust the volume too. After the DSP does all this processing, it converts the bits of data back to analog and sends it to the audio amp. The beauty of a digital hearing aid is that a single design can be programmed to be used by many people without changing the electronics. All you need to have customized is the ear mold to fit your ear. An audiologist connects the hearing aid to a laptop computer to program its many parameters. Take a look at www.hearsource.com to see an example of how you can program your own digital hearing aid. As always, don't underestimate the value provided by your audiologist. Consider self- programming as fine-tuning and let the audiologist determine your baseline. (I am not a hearing professional. Consult with your doctor and audiologist for expert advice.)

I have been wearing "digital" hearing aids for three years. Here's what I've learned.

The "analog" aids of yesteryear were nothing more than sound amplifiers. Some could have been designed as high pass filters/amplifiers for those who lost high frequency hearing. Those analog aids also "squealed" at times from feedback due to the "microphone" (called pickup) hearing sound from the "speaker" (called receiver).

The "digital" hearing aids today operate using I.C. chips for DSP, Digital Signal Processing, and are tailored for each individual's specific type of hearing loss. This is done by "programming" each DSP chip for each ear based on results of a hearing test in order to overcome each ear's deficiency. The result is a custom made hearing amplifier for each of your ears.

The "digital" hearing aids also are programmed to avoid the feedback phenomenon, although they are not perfect. The "digital" hearing aids come in a variety of styles (behind-the-ear, in-the-ear, in-the-canal, etc) to suit the taste of the wearer. Prices vary all over the map with the best price I've found at Costco (Siemans hearing aids) for about $1200 apiece to as much as $5000 apiece at other hearing aid providers carrying a range of manufacturers.

None of these devices is "cheap" but they are effective depending upon one's specific type of hearing loss.

Here's my brief explanation. Digital audio for a hearing aid can help in a number of ways. First it can (or should be able to be) tailored to your particular type of hearing loss. This means it should be able to amplify the frequencies you need help hearing and not amplify the frequencies you don't need help hearing.

It should also be able to reduce ambient noise, reduce feedback/screeching, and even more.

I found a good article at:

www.livestrong.com/article/32866-digital-hearing-aid-work/

if you want to read more.

The bottom line is, if the people selling these things do not know the features of the new units, then go somewhere else because they need to be tailored to you. If they don't know that then it won't be done and there’s no advantage to buying it. Except for perhaps the reduction of noise and amplification of voice in general.

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