Graphic equalizer

[Bassanova]

Hello.

I'm on the lookout for some kind of graphic equalizer solution for use in a home-made hearing aid.  My plan is to measure the hearing impairment and set up an audiogram (http://en.wikipedia.org/wiki/Audiogram), and make a combined equalizer/amplifier to neutralize the impairment.  But I'm at a bit of a loss as to how to make this equalizer.

Datasheet databases come up with several graphic equalizer ICs, but I haven't been able to track down any of them.  So I'm considering just making the equalizer by using standard opamps.  But I was wondering if anyone has any points of view on this.  Pros and cons regarding one method or the other.

Thanks!

 

[audioguru2]

.... home-made hearing aid.  My plan is to measure the hearing impairment and set up an audiogram (http://en.wikipedia.org/wiki/Audiogram), and make a combined equalizer/amplifier to neutralize the impairment.

You will probably make the hearing impairment worse. Boosting loud sound levels will damage hearing.
Real hearing aids have a compressor/limiter to clamp the levels to a safe level. Simple diode limiters and signal clipping will add high level severe distortion that is also bad.

Here is a graphic equalizer project. It is excellent so it is fairly complicated:
http://www.sound.westhost.com/project75.htm

 

[Bassanova]

You will probably make the hearing impairment worse. Boosting loud sound levels will damage hearing.
Real hearing aids have a compressor/limiter to clamp the levels to a safe level. Simple diode limiters and signal clipping will add high level severe distortion that is also bad.

Thanks alot.  I will take a look at that project later on today.  But a quick question.  What is the difference between a person without hearing impairment hearing a loud sound, and a person with hearing impairment and a hearing-aid hearing the same loud sound?  In my head I would think that the sound level recognized by the human brain would be the same in both cases, thus producing the same amount of discomfort.  Or is this not the case?

 

[audioguru2]

What is the difference between a person without hearing impairment hearing a loud sound, and a person with hearing impairment and a hearing-aid hearing the same loud sound?

A real hearing aid would limit the volume of the signal so that hearing damage does not occur.
The volume of a sound that is far less than a level to cause discomfort will damage hearing. So I think that the person with hearing impairment who has a real hearing aid will hear a very loud sound as being not too loud and certainly not uncomfortable.

 

[Bassanova]

A real hearing aid would limit the volume of the signal so that hearing damage does not occur.
The volume of a sound that is far less than a level to cause discomfort will damage hearing. So I think that the person with hearing impairment who has a real hearing aid will hear a very loud sound as being not too loud and certainly not uncomfortable.

This is a bit off-topic, but are you saying that a sound could be damaging a persons hearing even though it isn't discomforting, i.e. when listening to music and he/she increases the volume?  Note that I don't mean physical discomfort, like if the volume is so loud that the inner ears hurt, but rather that the sensation of sound is discomforting.

But I don't see how a loud sound can further damage the hearing of a hearing impaired person using a home-made hearing aid, when the sound isn't damaging the hearing of a person without hearing impairment.  When the sound is only amplified to the point of a normal level of hearing, I just don't see the difference.

I'm sorry if I'm harping on this.  On one side I want to make my grandfather's everyday life better, but, at the same time, I don't want to damage his hearing further.

 

[audioguru2]

Hi Bassanova,
Hearing damage occurs if continuous 80dB sounds are heard. 80dB is not very loud. The damage is mechanical, The tiny hairs in the inner ear that attached to nerves are broken by loud continuous sounds or very loud short duration sounds like from guns or from hammering.

The government regulates a max average level for workers for 40 hours per week to 85dB, but then an average person's hearing would have reduced high frequencies like a telephone.

Most hearing-impaired people lost their hearing due to sounds that were too loud. If your home-made hearing aid has a continuous output higher than 80dB to 85dB then additional hearing damage will occur.

I have protected my hearing all my life. I can hear low level and high frequency sounds. I am also a grandfather.