Costco messed up my dad's hearing aids for 3 years

It’s very interesting and understandable.

Sometimes when I’m trying to describe it to people, I’ll draw a sharp sloping V with little hashmarks for different decibels. And then I’ll explain that the bottom half of that is not functioning, so we have to turn up the volume. But when we turn up the volume, we wake up the neighbors and they start banging on the wall telling us to turn it down.

@Neville said:

I’m still on holiday, can someone else do the math for me and tell me approximately what sized vent that acoustic mass translates into?

I’ll try, but I have to find a math solver which I saved 1 year ago and can’t find it yet One year ago I have made an equation for fast transitioning diameter to acoustic mass (and vice versa), assuming constant length.

It worth be noted thats that equation in the second screen is very rough, which we see in R² = 0.59 value, which roughly means that cutoff frequency value can be determined by x (acoustic mass value) with 59% certainty.

@Neville said:

I’m still on holiday, can someone else do the math for me and tell me approximately what sized vent that acoustic mass translates into?

I assumed selfishly (see my audiogram) 500 Hz cutoff value:

Someone feel free to notice any mistakes. I am not a mathematician or a professional engineer.

First part is from graph in the second screen, second part is from first screen (Harvey Dillon book)

However:

@Neville said:

But 20dB in the lows is not normal.

For me, a 1.1 mm diameter is too large, and much noise enters through the vent then.

In my case, assuming roughly:
lenght of the vent = l ≈ 17 mm
Vent diameter ≈ 0.9 mm

It turns out that acoustic mass = 32 815 Henrys

therefore cutoff Hertz value in my particular case = 220 Hz.

Interesting Costco fitting problem: I got both a Jabra pro 30 and a Philips 9050 at Costco so I could compare them (and return one) before the 6 month return window expired. Had REM testing and adjust mentioned on both by the same Costco fitter. With the Jabra, I could barely hear the TV at the folks are were visiting and our ghost voiced we’re excruciatingly loud. With the Phillips, the TV came booming thru and I could barely hear our hosts voices. At the airport, with the Jabra, the voiced and PA system was crisp and clear. With the Phillips, it was garbled. I would expect that after REM and adjustment the two HAs would sound somewhat similar. This makes me seriously question Costco fitting altogether. I go back to Costco in a few days and will raise this issue with the fitter.

I too need a bootleg home audiology clinic LMAO

If I may ask, where did you get the supplies such as REM machine? as you can see by my audiogram I am a unique case, and in the future I will be self fitting.

eBay. Mostly available are Verifit VF-1, but you want to make sure it is verified working and expect to pay over $2000. Mine was medrx which don’t come up often and was $2500. You can get a Fonix FP 35 for under $1000 if it has the rem hookups but there is a steeper learning curve with those as they are 90s tech even though they were made through 2017. I have one that I use as a HIT box but I’ve done rem just for kicks and it matches the medrx but is harder to learn.

If you buy REM machines new, they are $5000-$15000 and, at least in the US, you need to be licensed.

@Bimodal_user said:

Oh, I forgot the most important cause of my purpose.

The more efficient earplug effect of my HA side greatly facilitates my CI ear isolation when I rehabilitate. It’s then as simple as turning down volumes maximally and turning off HA microphones OR simply turn off the Sphere.

With my new cShell my HA ear isn’t occluded as effectively and I can talk with someone in quiet situations even when I have no CI and HA turned on, with my cShell REOR values.

OH. Yes, that makes sense. So nothing to do with the gain of the hearing aid at low frequencies–I would be suprised if it was significantly affects with and without just a pressure vent.

But I was hoping to get an idea of what sized vent has an acoustic mass of 10,000 kg/m^4. I thought Henrys were current.

Edit: Goodness it’s been a long time, I got most of the way there but I forget how to manage dividing kg/m^2 by kg/m^4. AI tells me that if I assume a standardish earmold length of 12 mm then the diameter is 1.36 mm, but I have asked for confirmation from my father the mathematician.

But I’m just not sure I believe what this paper is suggesting (or what I’m interpretting with a rough google translation and my limited french for interpretting untranslated axis labels). I just find it super hard to believe that at -5 SNR that the difference between no vent and a 1.36 mm vent is 35% speech intelligibility. This doesn’t mesh with my patients’ experience, although it is not something I’ve looked at systematically. I’d need to see more in support.

Lour, something you might look in to, I recently got Jabra BTE’s from Costco and was having a terrible time with muffled speech and overly loud noises. Basically they were terrible to wear. My fitter changed my earmolds and that helped slightly, but when she switched the programing from the Jabra/Resound method (or whatever it is called) to NAL-NL2 it was like someone flipped a light switch in a dark room. Dramatic difference. I’m happy now.

@Neville said:

OH. Yes, that makes sense. So nothing to do with the gain of the hearing aid at low frequencies–I would be suprised if it was significantly affects with and without just a pressure vent.

When I occlude that 0.9mm vent with guitar string (not only in Sphere cShell, but also in Paradise) I feel it works a bit better when I increase the lows by 1-2 step in myPhonak/Amplifon app (roughly 2-5 dB gain). However it isn’t blinded randomized trial, so I can be biased much.

Even with that thing, new titanium cShells aren’t that occluding like M sized power domes placed past 2nd bend. Although my Paradise cShell have SDS 5.0 receiver, so it can be placed a bit deeper (or it had better fitted its shape to align with mybear canal wall) than Infinio SDS 6.0 with up and the same vent

@Neville said:

But I was hoping to get an idea of what sized vent has an acoustic mass of 10,000 kg/m^4. I thought Henrys were current.

Edit: Goodness it’s been a long time, I got most of the way there but I forget how to manage dividing kg/m^2 by kg/m^4. AI tells me that if I assume a standardish earmold length of 12 mm then the diameter is 1.36 mm, but I have asked for confirmation from my father the mathematician.

I’m sorry, I missed your request about 10 000 Henrys. My calculations are roughly similar, 1.34 mm assuming 12 mm vent length.

@Neville said:

But I’m just not sure I believe what this paper is suggesting (or what I’m interpretting with a rough google translation and my limited french for interpretting untranslated axis labels). I just find it super hard to believe that at -5 SNR that the difference between no vent and a 1.36 mm vent is 35% speech intelligibility. This doesn’t mesh with my patients’ experience, although it is not something I’ve looked at systematically. I’d need to see more in support.

Indeed, you surely are right. The purpose of that article is to show that chasing like “the more open, the better” is not necessarily much beneficial.

@DrJimmyJoeJimbob said:

Did you factor in the Heisenberg uncertainty principle?

lol just kidding but I’m bowing out of the math😂

Love that question. I have felt like Schrödinger cat during making that calculations…!