To repeat English Dispenser: I agree. Keep in mind is that fitting an aid for maximum comprehension requires knowledge and a specific skill set. The more severe and complex the loss the greater the skill required.
IMHO: A superficial or even a thorough knowledge of terms like db gain or loss is not enough. To handle the moderate/severe/profound losses you need a lot more. You need a modicum of understanding of the physics of sound plus the physiology of hearing. Ed
the point of the forum is to transfer knowledge right?
I agree with you absolutely!! People who donât want to transfer knowledge should not post at all.
This is something I barely understand. I am not an expert by far and my questions let me and others learn more. So far the concensus is that 0db is either impossible or nor desirable. I know two people who hear at 0db HL with CI in 1 frequency and an average of 10db in the rest. Isnât CI also subject to internal circuit noise?
Even if hearing at 0db didnât improve speech at 1 meter, wouldnât it still allow you to hear someone talking from across the room, house, hallway, building or some great distance? I know that you need +6db each doubling of distance. Also hearing at 0db would let you pick up very faint sounds as well.
Now, back on the topic of this thread,
Deaf123, my audiogram is:
(format: freq: right, left;)
250: 45, 45; 500: 40, 45; 1K: 35, 35; 2K: 25, 50; 3K: 55, 60; 4K: 65, 70
My hearing loss at 3K and 4K is 30 - 35dB greater than at 1K, yet my HA gain (ADRO comfort target) at those frequencies is 12 - 15dB (more than at 1K). In fact, the ADRO Maximum Output Level limits gain at those frequencies is set at 18 - 21dB) (More amplification is way too loud.)
I would focus on relative amplification rather than an absolute â0dBâ level, as being more useful in understanding hearing correction.
IMO, Zafdorâs post comes closest to explaining the âwhyâ of it here: http://www.hearingaidforums.com/showpost.php?p=26837&postcount=2
Thatâs like askingâŚ
If you have a car tire and rim that weighs 30 pounds and you put 30 pounds of air in itâŚ
âDoes the tire and rim combination now weigh 60 pounds?â
Inquiring minds want to know.
Shi-Ku Chishiki
No hearing professional who I have talked to has had thorough familiarness and skill with the subject. It has sometimes been difficult to get answers to simple questions like what some number or a curve means, and they have also made mistakes.
My hearing loss is diagnosed to be caused by otosclerosis. It is mostly conductive. Nevertheless, I have had a lot of trouble with loud sounds, and I have had the experience mentioned elsewhere where I got temporary hearing loss and tinnitus after a concert. That was even though my friend with normal hearing considered the volume level just right, and I was not wearing hearing aids. Around the time it happened the hearing of my right ear was about where my left ear is now, the left ear was better. Even though I may be unusually sensitive, usually when I have suffered about noise (without hearing aids) other people have complained about it too. When I had a louder close fitting I suffered not only for loudness but also an occluded sound. Until loud sounds were taken softer I used to think an open fitting much better than a close fitting, and reducing loud sounds helped a close fitting to sound natural without an occluded tone.
Kind regards,
Leia
Does anyone know why? Is there a way around this by reducing SPL/MPO? It goes on to say that hearing at 0db overamplifys(too loud) you and results in distortion. If someone has 70db HL and a 0db sound is amplified to 70db, that person should just barely hear a 0db sound. How can it be too loud? As for a 30db sound, donât give 70db gain, use compression so a 30db sound is only getting 55db gain, but a 0db sound gets the full 70db gain.
If someone canât benefit from hearing at 0db, would 5db or 10db be far easier to be able to tolerate? Also why arenât maximum gains always used in severe-profound hearing losses so you can hear aided at 25db or better so you understand the most speech and hear the most sounds?
Deaf123,
Take a look at this ADRO Compression video, which will give you a more intuitive feel for how hearing aids operate with the reduced dynamic range that an HOH person experiences.
Thank you for an interesting video link jchunter. What comes to WDRC aids and Deaf123âs questions (I couldnât get to the link though), one way to look at it is that maybe technology has developed faster than the audiology field itself. The book Textbook of Hearing Aid Amplification which is published 2000, so almost ten years ago, talks about possible distortion when the dynamic range of a hearing aid is restricted, on page 113, referenced again to Hawkins 1984. When I tried mpo down with much newer Savia hearing aids it was a success. I use it with a close fitting for microSavia 100 dSZ and an open fitting for Savia 211 dSZ and they are both handling it well.
Kind regards,
Leia
The fundamental problem that most HOH people have is that they can not hear the complete range of sound loudness that ânormalâ people can hear. People with perfect hearing can hear sounds that range from the softest whisper to sounds 100dB louder. However, HOH people may be only able to hear the loudest 40dB.
Early attempts at dealing with this reduced sound dynamic range of HOH people began when hearing aids were still analog. Some of these early circuits just clipped the loud volume peaks, which introduced harsh distortion at the clip points. You can think of this in terms of the above ADRO video as attempting to âeraseâ the (loud) upper portion of the first scene of the video.
Later attempts operated by âcompressingâ the entire sound dynamic range, which eliminated the harsh clipping distortion but introduced other subtle distortions (visualized by the second scene, where the people appear squashed vertically).
Today, we have ADRO and WDRC sound processing algorithms for digital hearing aids, which both try to eliminate the compression-induced distortion. Here is a link to additional information on how these algorithms operate.
Thank you for the new link again jchunter. The analogy with pictures is helpful in some way, but the actual sound experience I have is different. If we look at the picture with human figures, after the picture is squashed it doesnât look right. However, the sound picture I get with a reduced dynamic range is still full. I couldnât tell the voice has less dynamic range by listening, I only hear that loud sounds are less loud. Either it has been worse with older equipment, or âdistortionâ here refers to a subtle difference in the voice which is not easily recognised.
Kind regards,
Leia
Yes. The squashed figures ARE distorted by trying to compress the entire dymamic range into the limited HOH range. This picture illustrates the problems (side-effects) of pure compression.
So, todayâs HAs use different methods. Oversimplified explanation:
ADRO tracks sound loudness and provides just enough amplification to maintain it in the userâs Comfort zone (just the userâs reduced dynamic range) - without much, if any, compression.
WDRC operates by compressing just the loudest sounds that exceed a âknee pointâ that the audiologist enters, along with attack & release time parameters.
The way my high frequencies have been compressed is so that they are most likely never coming out of compression. Would attack and release times then lose their meaning and not be used at all?
Kind regards,
Leia
Has anyone seen this post or my others? I still donât have many answers 
You have lotâs of good answers. Unfortunately you seem to still be missing the forest through the trees! 
You need to get over simple sound pressure levels and move onto understanding the dynamics of speech. If a hearing aid could amplify every sound perfectly to a comfortable level for you in real time you still would not have hearing that was normal; e.g. the trailing âsâ on a word is not supposed to be as loud as the vowel that just proceeded it. Once your hearing is degraded in itâs dynamic range, comprehension will suffer.
Finally, something that I understand and makes sense.
However, thereâs something wrong with that idea⌠rather loud speech is crystal clear with my hearing aids, yet they are in huge compression. I also recall reading on some acoustic book that relative loudness of sounds carries only very little information, but I donât have the book here.
Kind regards,
Leia
pretty much no one uses adro anymore.
the old savia used to, now they have steer awayâŚ
What if someone(such as me) wants to hear environmental sounds as good as a hearing person, could 2 programs be loaded on the HA, one that optimizes speech and the 2nd one that gets you to 0db or as close to 0db as possible so you hear all the sounds a hearing person can? Check post 28, id like to understand why that ebook says 0db is too loud if you limit the SPL/MPO.
Speech has a 40db dynamic range, but you do need to get to 15db aided to be above the speech banana. Ok, say we forget about 0db, is it true the worst your hearing can be is 85db HL in order to get to 15db aided with HAs offering 70db gain? I do know you wonât understand 100% speech because of distortion, but youll understand a high percentage on the basis you arenât outside any part of the speech banana.