Hi.
Could this microphone be a good match with the hearing aid?
AOM-5024L-HD-R
Omnidirectional
Singel ended electret.
Sensitivity: -24dB
Signal to noise: 80dB
Maximum SPL Input: 110dB
True 20 Hz to 20 kHz performance
Diameter: 9.7mm
Height: 5mm
$4.94 per unit at digikey.
Hi,
Wow, that’s a pretty nice and comprehensive data sheet that you found. Often, the datasheets for microphones are very poor in detail, even for microphones from good vendors.
Looking at the microphone that you have picked, it appears to be a pretty good one. I don’t have a lot of experience, but I think that your microphone compares pretty well to this Knowles EK-23024 that have played with a little bit.
One difference is that I think that the sensitivity of your microphone is higher, but that’s not particular a good or bad thing, just different.
To me, the most important number is the self-noise of the microphone. No microphone ever reports its self-noise directly, but it can usually be inferred from the data. For example, if your mic says that the max SPL is 110 dB and the signal to noise is 80 dB (A-weighted), that means (to me) that the self noise is ~30 dB-A SPL.
While 30 dB SPL is pretty quiet, once you put +30dB of gain via the Tympan, now you’ll hear a steady noise floor at 60 dB, which is definitely annoying to normal-hearing people. So, if one truly has a hearing loss, it may be fine. But, if you’re going for super-hearing using the Tympan, you’ll hear a good amount of hiss.
For comparison, I think that the lapel mics that I often use with the Tympan have a self-noise around 35 dB SPL (I think). So, you’re mic is better. I think that my Knowles mic is ~26 dBA, so the Knowles mic is a touch quieter… The Knowles mic, though, is much more expensive ($16?), its frequency response isn’t very flat, and I don’t think that it goes up to 20kHz. Also, the Knowles mic is a 3-wire device (which Tympan supports) whereas yours is 2-wire (which Tympan and a tons of other devices support).
Personally, I think that you’ve found a pretty decent mic element. I’m curious to try it myself.
Chip
Oh, also, you should be aware that there are mics intended for general applications (like the one you found) and a whole different category of mics intended for hearing instruments (aka hearing aids).
The Knowles mic (and bunch more from Knowles) are hearing instrument mics. If you google the Knowles mic model number, and go to the Knowles page (not the Digikey page), you’ll see a few of the other hearing instrument mics that they have, for comparison.
I’m not saying that hearing instrument mics are better or worse than general purpose electrets, but they probably do warrant special attention if you want hearing-aid-like behavior.
Mostly, though, I’m just making you aware (if you weren’t already) that there is a whole genre of mics for this purpose.