What is the difference between gain and volume

Hi all:
What is the difference between gain and volume?
What is the meaning of MPO? Is it the same as compression?
What is PC, attack and release time compression?
If I feel the sound is thin and sharp and sometimes too sharp to hear people’s voice, what should be the adjustment?

Thanks to anybody who will respond to this.


Hi analoglover

Let me take a shot:

Gain refers to the amount of “boost” applied to a specific part of the audiogram. You might add , lets say, 20db of gain to the 250 Hz band, because you have 20 db of loss there. You would add a different amount of gain (depending on the audiogram) at 2000 Hz. The gain would be different for each frequency band. These bands are what allows the hearing aid to compensate for losses at specific frequencies.

Volume raises and lowers the final output of the hearing aid (all of the frequency bands together), just like the volume control on your radio. Volume won’t change the way something sounds, it will just make it louder or softer.

MPO stands for Maximum Power Output. This is the absolute loudest your hearing aid can go.

PC stands for Peak Clipping. When sudden input sounds are too loud, the hearing aid can “clip” the tops (peaks) off the sound waves so they don’t damage your hearing, or become too uncomfortable. This clipping lowers the volume, but also adds distortion to the sound. I believe this is what causes a sort of “buzzing” sound to voices when they’re too loud. Not 100% sure about that last part.

I’ll defer the last question to one of our resident professionals, but my guess would be that there is too much high frequency gain. Are these new hearing aids for you? Except for not being able to understand voices, that’s a pretty common complaint from new hearing aid wearers.


Hi Dag:
Thanks for explaining me so detail for my questions. Actually, I am a very experienced hearing aid user. I have been wearing hearing aids since 1988. All of them are analog. The one I am wearing is still programmable analog. It is the best one but unfortunately Beltone stopped producing since 2005. I am trying to find another hearing aid to replace it. The only one I got is Oticon Ergo. However, it seems the sound is very thin and sometimes too sharp or loud. It’s better after the dispenser lower the low frequency, the slamming of the door and banging on the table is all clear now. Now is the speech seems too sharp so that I cannot hear the speech. Do you think I should use AGO fast to improve the speech or lower the overall gain.


Hi analoglover

“Do you think I should use AGO fast to improve the speech or lower the overall gain.”

Since I’m still new to hearing aids, and have only worn digital, I’m really the wrong person to try to give you that advice. So I’ll defer that to one of our professionals.

Since being told that I needed HAs, I’ve done quite a bit of reading, and I’m an electrical engineer by profession, so I understand some of the basic terms. Google helped with the rest. I’m sure you’ve read the same threads I have, showing that long term analog wearers can have problems adjusting to the very different sound of digital HAs, and that most digital instruments can be programmed to mimic an analog aid (assuming that your loss is within the fitting range of the specific HA). Having said that, I’m at the limit of my experience. :o Good luck with your search.


you can make any instrument to sound more or less analogue
by making it linear (ie: compresion: 1 )

Hi Xbulder:
My question is do you think I should ask my dispenser to use AGO fast or to lower the gain or a combination of both to make the speech clear.
Also, you mentioned that digital can be made to linear by compression 1. What that means? Also, what is kneepoint? What is frequency crossover?




What is Compression?
Amplifiers are classified as either linear or nonlinear on
the basis of their decibel input/output transfer function.
The level of the output of the amplifier is plotted as a
function of the level of input to the amplifier for a pure
tone at a particular frequency (ANSI S3.22, 1987; Australian
Standard 1088.2, 1987; IEC Standard 118.2, 1979). In
the case of linear amplification, the relationship between
input and output is one to one. Compression amplifiers are
not linear, and the input/output function is less than one to
one for static signals (see Figure 1). The amount of gain
applied to the signal varies automatically, depending on
input. Walker and Dillon (1982) describe the effect of
compression as the dynamic range of the output being less
than that of the input. In order to understand compression
systems, it is necessary to know the static and dynamic
characteristics of the compression amplifier, and the effect
of the compression system on the hearing aid response.

Uh huh. Wanna translate that into English?:rolleyes:

Translation: from Tekno Speak to English …American style.

Hard of hearing persons almost always have a diminished dynamic range…meaning they can’t hear soft sounds and loud sounds distort and are uncomfortable.

To handle this problem digital hearing aids compress the loud sounds down to a comfortable level and boost the soft sounds up so they can be heard. This is called non-linear amplification or compression.

All aids amplify the sound to compensate for the diminished sensitivity. Sound is calibrated in decibels (db) which is a measurement of how loud the sound is.

The normal mammalian hearing system (yes you are a mammal) is extremely sensitive to soft sounds but naturally compresses loud sounds. That means that to a normal ear a perceived loudness of twice as loud is in reality 10 times louder.

To hard of hearing 10 times louder is perceived as 10 times louder (not twice as loud like a normal hearing person hears) This condition is called Recruitment.

All aids have a MPO or maximum power output circuit to limit very loud sounds. All MPO’s cause some distortion (lack of clearness) if pushed too far.

Attack and Release times are how fast in milliseconds the compression responds to loud sounds. You see the amplifier in your hearing aid normally amplifies linearly meaning that a 65db sound is amplified by whatever the gain adjustment setting is for that particular tone say 25 db.

So 25 plus 65db means that 90 db’s of sound would be put into your ear. That’s quite loud and might be uncomfortable. So the computer in your aid senses that (knee point) and cuts the amplification down to a comfortable level. But this takes time to detect and operate…that is the Attack time. Now after the loud sounds cease, the amplification is returned to normal…the Release time. Ed

1 Like

Hi dag, ed, xbulder,
Thanks for the detailed technical answers.
Two questions:

  1. What is frequency crossover that is available in Beltone CSP-II HA?
  2. For Oticon Ergo, it doesn’t say the kneepoint, it just states that it has UCL and AGO fast and slow or PC. What is the kneepoint for compression to start working?
  3. For programmable analog hearing aids like the above 2 mentioned and digital HA, I know digital HA has more for adjustment, what makes them different in terms of sound quality?
  4. I have tried Beltone one before, however, I felt the sound was very low tone and therefore I returned it. Do you think the attack and release time fast will correct the tone from low to higher? That is, better speech.
  5. Go back to Oticon Ergo, is that means I should lower the gain a bit(now is set at maximum, for Concha, max is 51 db average) and then the compression from PC to AGC fast? You think I should use AGC fast or slow. My lost is 40 db in 250db and curve downwards to 70db in 6000db.
  6. Finally, is that means all digital hearing aids will be the same given that they have the same adjustments? I don’t think so.


Thank you!

I don’t know about Beltone products, so can’t help you there.

The Ergo has a limited range of adjustments, since it is a single channel device. You can cut the low frequencies or hi frequencies with the audiogram control, and you can adjust the output limiting method (there is no way to directly change the kneepoint).

Here are the three output methods:

Peak Clipping: Best for severe losses, provides the highest possible output

AGCO fast: Like traditional AGC + PC, low distortion

AGCO slow: Confortable, low distortion limiting with minimal pumping effect, best for mild/moderate losses.

Hi Analoglover,

I am in the same position as you and I love analogs however I am trying to Unitron Moxi Yuus and so far I like what I hear. Few teething problems but that is hopefully to be resolved by a custom mold :slight_smile:

oticon doesnt like you to change a lot of things…
I wish they give you the option…
They used to have something call a tool to measure the MCR, which they took away… I had the most confortable fits, using this tool…
Aparently they do not like people to have much control