bump, learning more all the time!
Savia is not an adro hearing aid.
Kind regards,
Leia
What if the hearing loss at a certain frequency is already at NR (like my case) does it mean you can apply your preferred gain? 
We know that, beyond certain threshold there is no use in using amplification
because that cochlear zone is dead. the ideal option is to use either frequency
compresion or frequency transposition. Avr Sono had been doing freq compr for a very very long time. Phonak had popularized frequency compre. and it calls it sound recover.
Widex, had used freque. transposition in their inteo line for quite some time-
Im not sure they have been that sucessful. Most people reject transposition and it
requires a adaptation time⌠But the results are promisingâŚ
We are approaching the 2nd wireless products from phonak, siemens and Oticon.
I would expect siemens and Oticon to consider some sort of frequency transposition
products. We would know in april âŚ
bump
Really interesting information
dBHL is a measurement specifically for hearing loss â it is a weighted scale used to âflattenâ the ears response at differing areas of sensitivity (and audiometers are designed accordingly) â it cannot be used to compare or measure anything else except on an audiogram ---- gain on the other hand is the difference between input and output so to use these two terms together is in fact a non starter - they do not equate in any way.
In addition there are all the other things discussed hereâŚ
The big thing to remember about gain is that it is an amount of additional volume for any given input (or output depending on the hearing aid). So, if you have 30dB of gain it doesnât mean you are hearing sounds at 30dBâŚit means that you are hearing sounds 30dB above a specific input of sound. For example, say our hearing aid looks at gain for 3 input levels, 40dB, 60dB, and 90dB. If we just looked at the middle one, 60dB, and assumed a 30dB gain amount, that means sounds at that frequency would be heard by the wearer at 90dB (60+30). So if you had a hearing loss of 75dB at 3000Hz, and had gain of 30dB at 3000Hz, a sound at 60dB at 3000Hz would be heard at 90dB which is 15dB above the wearers threshold and should be easily audible. Now this is very simplistic but illustrates the concept of gain and how it works/is applied.
This may become more understandable next week when I get my first ever pair of HAs.
For someone with my hearing loss chart I do not understand why HAs cannot just act as small equalizers and simply boost the volume of a certain range of high frequencies.
I think my chart means I can still hear certain high frequencies but for instance, at 8000 they have to be 80dB louder than for a ânormalâ person. So if the hearing aid were able to boost sounds in the 8000 frequency range by 80dB without too much distortion or feedback then I would hear them and all would be well.
As I understand the Phonak SoundRecover feature it transposes high frequencies to a mid range one and mid range ones to lower ones and compresses the difference to fit the high ranges progressively into the lower ranges whereas other HAs simply transpose them so that high and mid range sounds are both duplicatively heard as the same mid range sounds. I am not sure I am going to like this which is why I checked whether this feature could be turned off. I think I would like the simple transposition even less. I wish that simple equalization worked. But until I get my HAs I wonât know.
You are not applying gain correctly. We donât use 0dB HL as a reference for gain. Gain is an amount of amplification over a certain input or output so if you have an input of 60dBHL and you had 80dB of gain, the sound would be 140dB HLâŚso that obviously doesnât work. Also, the goal of hearing aids isnât to try to get your hearing thresholds to 0dBâŚitâs to restore hearing to an audible level for normal conversational speechâŚso usually if we do aided testing after, thresholds are usually 15-30dB HL because normal conversational speech happens around 55dBHL. Hereâs another kickerâŚhearing aids function in dB SPL and not HL which is an artificial scale created so that hearing within normal levels it can be plotted in a nice, straight line (because everyone likes straight lines).
But wait, THEREâS MORE!!! Hearing loss in the high frequency range results from outer hair cell damage. If there is enough hair cell damage it results in essentially dead areas of the cochlea, so it doesnât matter if you could generate a million dB of gain, thereâs nothing there to send the signal to the brain. Soundrecover takes the sounds that would potentially fall in the cochlear dead regions and compresses them to an area where there could potentially be some lingering functional hair cells allowing the wearer to hear that /s/ sound whereas before they might not be able to.
To simplify a hearing aid, it is basically a very high -tech equalizerâŚapplying amplification of varying amounts where you need it plus tons of other features like noise reduction and all those other fancy things you get with hearing aids.
Thanks for the correction on âgain.â
I do not understand your comment on why boosting an input of 60 dB to 140 db at a certain frequency doesnât work (for me). If itâs at 60 dB I donât hear it and if boosted to 140 dB I would hear it as 80 dB. Why doesnât that work?
I understand some of my hair cells are dead or damaged, but not all (yet, thank God) as I can still (I guess) hear some high frequencies (again, I guess if they are loud (or amplified) enough).
So in simplistic terms if the HA acted as an equalizer but with a reverse (or uphill slope), then that in combination with my hearing downhill slope results in a straight line, nâest pas?
The basics of correcting hearing loss are not about matching your loss to an amplifier that cancels it out, otherwise we would all have perfectly corrected hearing. Once sounds reach 100-120dB, even someone with a profound loss will find them too loud (read up on recruitment).
The way to think about how difficult it is to correct your loss is how much usable dynamic range do you have. Someone with perfect hearing would have about 100dB, hearing that mouse scurry across the rug (0dB) as will as tolerating a door slam (100dB). Now, if you have a flat loss of 70dB, you have only 30-40B of usable range. The job of the hearing instrument is to put that 100dB into the 30 dB you have left. In general, you will need voices 20-30dB above your hearing threshold before you can start understanding them as words, and this further complicates things. These are the reasons modern digital instruments work so well, a simple analog amplifier just canât do this kind of stuff.
From a previous thread:
OK, it comes down to the application of gain.
First you have to understand that these numbers we throw around on here 80-90-100 dB arenât a linear scale. To put it simply, if one speaker puts out 80dB and you put another speaker right next to it you produce a whopping 83dB. So a doubling of âpowerâ equates to a 3dB rise in measured output.
The next thing to take into the equation is that thereâs a reasonability test applied to gain which forms the basis of all gain calculations. IE: how much sound is âneededâ to hear whilst staying within peopleâs UCL or uncomfortable loudness levels.
The third aspect is that the inputs we have been discussing (speech) arenât 65dB AVERAGE, they are 65 dB âpeakâ value. The average value is about 30-40dB depending on the mix of ambient and speech proportion.
The fourth part of this is that given all of the above, engineers determined in the 50âs 60âs 70âs 80âs and 90âs refinements to the basic concepts so that you donât break some fairly fundamental ârulesâ of gain.
Namely: 1/2 gain and 1/3 gain rules, basically that if you have a conductive hearing loss, you will receive Half that amount back in gain, at the appropriate frequencies. If you have sensorineural loss, that will be 1/3 or less. Now in our fancy digital age, there are systems that deviate from this to an extent, but thatâs the basic precept.
So, if you have a 60dB loss, on average, youâll get 20dB gain on average. Which, even on a 65dB input signal doesnât put you anywhere near the 85dB (Aleq), simply because the average dose of continuous speech at 85dB is going to be around 40-50dB. Any more than this is going to do your swede in as youâll get Auditory Fatigue from the long term exposure.
To combat this, for the last couple of decades hearing aids have been built with circuits that incorporate compression - compression is a technique which allows louder sounds to be given less gain while still amplifying the quieter ones. This has the beneficial effect of making the quieter sounds audible but not blowing your head off with the louder sounds. Now, youâll hear some people saying that compression is bad, and linearity is good, especially for music. Yes, this is true to an extent, but, non-believers, listen-up! youâve had some degree of compression in your analogue aids for years - go and dig out the old Gennum and K-Amp specs if you like - or even ask Mead Killion (if heâs still going around on his unicycleâŚ) Basically all circuits compress the output to some extent to avoid the receiver clipping - overdrive distortion on the sound. ~(output-limiting compression)
And finally, just when you think that the manufacturers are really going to do you down, we have software. All the stuff you can see, and all the stuff you cant. Hereâs a thought: wouldnât it be a really good idea to put a limiter into ALL hearing aids? Just to keep the Lawyers happy and to stop self-programmers from really doing damage? Well, what if we put in default UCL limiters at 105-110dB? So that the peak values of the output wouldnât do any real harmâŚYou can override them of course, but thatâs at your risk.
Just think, if somebody fires a gun near your head with occluding hearing aids in - youâll experience less hearing damage than the person who fired itâŚ
So, there it is, in a nutshell. Hearing aids listening to speech are unlikely to damage your hearing further. I hope that doesnât sound too patronising. If you want more info, try to get hold of the excellent book: Hearing Aids by Harvey Dillon or Andi VonLanthenâs one.
So I got my first ever HAs this morning (Naida S IX CRTs). Greatest things since sliced bread.
Anyway regarding SoundRecover it has to be on or off for all the four automatic transition programs, but it can be selectively on or off for a manual program.
So initially I have a manual music program with all the same settings as the automatic music program except sound recover is off. I donât know yet which I will like, but I am happy it is doable.