Hearing Aid Compression and Amplification software algorithms

pvc

pvc

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I am trying to visualize-and-simplify the function of the typical (Compression and Amplification) software algorithms used in hearing aids for correcting a hearing loss. Insomuch as I understand the problem to be corrected, a HoH person has lost the ability to hear the full (decibel-range/intensity/loudness) from zero to 120 dB. So the low intensity sounds such as whispers are gone (can't hear them) and maybe even the moderate intensity sounds are difficult to hear.

Yes, the hearing loss may also vary in Frequency/Pitch in cycles per second (Hz). But for the sake of simplicity, I would like to focus on the ability to hear the full (decibel-range/intensity/loudness) from zero to 120 dB.

The below middle image (speech banana) represents the full (decibel-range/intensity/loudness) from zero to 120 dB to describe the intensity/loudness of certain sounds, and it also represents the Frequency/Pitch (from 125 to 8000 Hz which we are ignoring for now).

The below Left image represents an Oticon 85 receiver for a moderate hearing loss (ignore the dark gray lines for now which attempt to show the difference between an open vent fit and an occluded sealed-or-small-vent fit). For the power=85 receiver, the full (decibel-range/intensity/loudness) from zero to 120 dB will be compressed and sufficiently amplified to fit into a range of (zero to 85) dB.

The below Right image represents an Oticon 105 receiver for a severe or profound hearing loss. The full (decibel-range/intensity/loudness) from zero to 120 dB will be compressed and amplified to fit into a range of 20 to 105 dB.

sb8.jpg
 
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Interesting, it looks like the Oticon 105 receiver wouldn’t get to “th” and “s.”
 
Well, you may still hear “th” and “s”.

In laymen terms, normal hearing from (zero to 120 dB) for a total of 120 dB is compressed and relocated to where you can hear it even with your hearing loss. It gets compressed and amplified into the new range where you can hear, in this example the target range of (20 to 105) or 85dB in total.

So, you can still hear “th” and “s” because it will be amplified/louder. Though the downside is, you won't have the full range (0 to 120 dB) anymore because it has been cut down to a range of (20 to 105 dB) or 85dB in total.

A bigger downside (for someone with really profound hearing loss) is that you may run out of space to accept the new hearing range because the top of the target range is limited and not infinite.
 
Caveat: I am not an expert on how this works, and this is only my understanding in laymen terms.

The reason I bring this up is that I saw another topic (in a galaxy far, far away) where musicians were seeking a way to turn off compression. Yikes, compression is used to repair your hearing loss. You can't just turn it off! There are other things that can be done instead, And we would have to get into discussing the other scale of Frequency/Pitch in cycles per second (Hz) and not just the decibel/dB range of (0 to 120 dB).
 
pvc said:
Well, you may still hear “th” and “s”.

In laymen terms, normal hearing from (zero to 120 dB) for a total of 120 dB is compressed and relocated to where you can hear it even with your hearing loss. It gets compressed and amplified into the new range where you can hear, in this example the target range of (20 to 105) or 85dB in total.

So, you can still hear “th” and “s” because it will be amplified/louder. Though the downside is, you won't have the full range (0 to 120 dB) anymore because it has been cut down to a range of (20 to 105 dB) or 85dB in total.

A bigger downside (for someone with really profound hearing loss) is that you may run out of space to accept the new hearing range because the top of the target range is limited and not infinite.
Click to expand...
I am surprised, I tough Phonak was the only doing this:
relocated to where you can hear
Click to expand...
 
pvc said:
Caveat: I am not an expert on how this works, and this is only my understanding in laymen terms.

The reason I bring this up is that I saw another topic (in a galaxy far, far away) where musicians were seeking a way to turn off compression. Yikes, compression is used to repair your hearing loss. You can't just turn it off! There are other things that can be done instead, And we would have to discuss the other scale of Frequency/Pitch in cycles per second (Hz) and not just the decibel/dB range of (0 to 120 dB).
Click to expand...
I thank you for that effort to bring your understanding, I think this is how we all learn more to deal with our unschooled knowledge of programming a HAIDs
 
I am surprised, I tough Phonak was the only doing this:
Click to expand...
No, all hearing aids will compress and amplify (decibel-range/intensity/loudness).

I think you are talking about Phonak's Sound Recover 2. This takes a range of Frequency/Pitch in cycles per second (Hz) and relocates those into a lower frequency range where you can hear it. It is not (decibels/dB/intensity/loudness). Also, other hearing aids have this capability (not just Phonak) and it helps some ppl who no longer hear birds tweeting and such because they have lost hearing in the high frequencies.

This frequency lowering only works for some ppl who are good candidates for frequency lowering.
 
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Think of decibel-range/intensity/loudness this way;
  • someone is whispering in your ear in a barely audible voice
  • someone is yelling at you with a very loud/high dB voice
  • decibel-range/intensity/loudness is depicted vertically on the chart
Think of Frequency/Pitch in cycles per second (Hz) this way;
  • someone is playing Bass on drums
  • someone is playing highs on a violin
  • Frequency/Pitch in cycles per second (Hz) is depicted horizontally on the chart
 
Sorry, it gets murky for me when discussing Frequency/Pitch in cycles per second (Hz) and I don't know much about what hearing aid algorithms do with Frequency/Pitch?

Part of my understanding is that frequencies are related to each other in a curve and any change to one frequency affects the neighboring frequencies. When a hearing loss is not curved then it is difficult to fit, for example Cookie bite hearing losses are very difficult to fit properly.

Cookie-bite-hearing-loss.png
 
Oh, okay. Still TRYNA describe and show this in pictures o_O When the full range of hearing is compressed into a range that you can hear, it is not compressed equally among each of the frequencies 125, 250, 500, 750, 1000, 2000, 4000, 6000, and 8000 Hz. Instead, each of the frequencies is amplified individually (and on a curve) related to your measured hearing loss from your Audiogram.

sb8-jpg.746
 
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And here's an image showing frequency lowering (or Phonak's name = Sound Recover 2). The image shows ten different configurations for ppl who may not be able to hear sounds in the 4000-9000 Hz range that could possibly be moved to a lower frequency range. Of course this would also change the sound to a lower pitch, and, it doesn't work for all hearing losses.

I would like to emphasize that frequency lowering is a separate procedure and not part of your Rx/Prescription that is calculated by the fitting software to "fit" your hearing loss,

c2.jpg
 
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Sorry, my original image constructed from 3 separate images is not correct because the left side of the image implies that you can only hear sounds up to 80 dB. It is difficult to represent with existing images because the right and left parts of the image were designed to show the capacity/power of the receiver/speaker.

Pfft; maybe trying to explain this with multiple existing images is confusing and doomed to failure.

Anyway, we have already described this in another forum topic→ What is the objective of hearing aid fitting software, and documented the same in a DIY School PDF File named (How Hearing Aid Gain Fits Your Loss).

This attempt to provide a simpler explanation ain't working.
 
pvc said:
And here's an image showing frequency lowering (or Phonak's name = Sound Recover 2). The image shows ten different configurations for ppl who may not be able to hear sounds in the 4000-9000 Hz range that could possibly be moved to a lower frequency range. Of course this would also change the sound to a lower pitch, and, it doesn't work for all hearing losses.

I would like to emphasize that frequency lowering is a separate procedure and not part of your Rx/Prescription that is calculated by the fitting software to "fit" your hearing loss,

View attachment 751
Click to expand...
“S”uper interesting! No time right now but I will check it out with time. Thank
 
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pvc said:
Sorry, my original image constructed from 3 separate images is not correct because the left side of the image implies that you can only hear sounds up to 80 dB. It is difficult to represent with existing images because the right and left parts of the image were designed to show the capacity/power of the receiver/speaker.

Pfft; maybe trying to explain this with multiple existing images is confusing and doomed to failure.

Anyway, we have already described this in another forum topic→ What is the objective of hearing aid fitting software, and documented the same in a DIY School PDF File named (How Hearing Aid Gain Fits Your Loss).

This attempt to provide a simpler explanation ain't working.
Click to expand...
 
stumbling into this late. But Frequency is more important to understand than gain I would think.
Gain refers to HOW MUCH power you have - or how much volume a sound is delivering.
Frequency IS the sound. So without considering the frequency... what could anything mean?
Compression refers to loud and soft input sounds being treated differently so that output can fit within your hearing by being above your minimal ability to hear IN THAT FREQUENCY RANGE, and below both your UCL Uncomfortable loudness level and the MPO Maximum Power output limits of the speaker( receiver )

Other considerations are feedback that could occur which require limiting output in loud and high frequencies.
Attack and decay times of the sounds.
The value of the sound which is keenly related to the frequencies and the environment.
Then there is the DIRECTION of the sound in relation to the angle of your mics on your hearing aids set to pick up sounds from what angle.
The prescription rationale is a profile of the behavior of the hearing aids and their plan to favor certain situations, such as speech for persons with varying loss.

Todays aids are microprocessor computers that try to analyze what the sounds are coming from and what particular frequencies, and much of the above... are most likely to be of importance in your understanding of speech within the current situation.

So you really need to become sensitive to all that the visuals within the fitting software mean, the theory of how all the above behaves, and the various modes and options the instruments are capable of.

Without understanding a lot of the above, you can be very frustrated, constantly dealing with lesser performance, and even suffer damage of various kinds.. depending on your sensitivity and discernment.
 
From my non-professional understanding, Gain is not the same for each frequency. Instead, Gain is applied to frequencies that need Gain, using one of the various formulas that are available. The formula also must take into consideration that each frequency is related to neighbouring frequencies in a curve.

Another way to look at it; Gain is not the same as increasing Volume. Increasing volume would apply an equal amount of gain to each frequency.
 
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pvc said:
From my non-professional understanding, Gain is not the same for each frequency. Instead, Gain is applied to frequencies that need Gain, using one of the various formulas that are available. The formula also must take into consideration that each frequency is related to neighbouring frequencies in a curve.

Another way to look at it; Gain is not the same as increasing Volume. Increasing volume would apply an equal amount of gain to each frequency.
Click to expand...
My non professional understanding does not understand this use of English. Gain is a word that could be substituted by the word "intensity" or the word "level". For each frequency, gain may be increased or decreased, or left alone. No frequency is an island unto itself as far as the management of frequencies go, so there is a curve-like gradation that results in changing any frequency's gain (actually any range of frequencies) blending a response with the requested responses of adjacent frequencies.
 
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