The best hearing aid for very high frequency loss

It actually takes more energy to drive a subwoofer than to drive a tweeter. You need a pretty powerful amplifier to deliver the thumping sound the subwoofer can generate. But you need hardly much to drive a tweeter.

I’m not sure what you’re fuzzy about, though. Yes, a tweeter is bigger then the most powerful receiver, but the tweeter can also deliver a lot more sound intensity (or sound energy). The sound intensity is inversely proportional to the square of the distance, so the closer the source is placed to your ear, the less energy it needs to produce the sound with enough pressure/volume for you to hear. That’s why the receiver can be small, use much less energy, but still able to deliver the kind of volume you need to hear -> because it’s right inside your ear canal.

Not necessarily, but if you make a transducer that ‘wants’ to resonate at 12000 Hz, the stiffness of the beam is going to be unable to reproduce 250Hz at a decent level.

So you have to choose where you deliver the response. Through clever damping and a few electro-mechanical cheats you can get about 200-10,000Hz with a peak resonance around 2-3KHz or roughly where your ear-canal resonates.

And as you make receivers capable of generating more gain, the beam becomes more stiff, it’s ability to resonate at distances further from the peak will decrease. I think the Signia S receiver can do 100-10500, but the HP only 250-5200. Higher power (stiffer beam) means that it can’t generate as low or as high as frequencies as a thinner beam? Is that a reasonable semblance?

The engineers are not audiologists in the first degree? Sarcasm over. The first hearing aid I had 15-yars ago claimed 6-kHz. 5-years later 8-kHz was the claim. 5-years after that it was 10-kHz but the highest adjustment their software package would allow was at 8-kHz. Obviously the engineers are working on high frequency improvement. I see a trend here and they have be begging for more.

High frequencies take much less power to amplify. The transducer excursion is microscopic. Low frequency requires much more power to move the air that transmits sound to the ear. The transducer excursion is much greater. High frequency is directional, low frequency is not. That brings up another point. I have very little sense of direction with the hearing aids I have owned. As far as bandwidth, I’m talking flat response from about 6 to at least 12-kHz, not something that starts rolling off and is down 20-db at 12-kHz.

Audio without high frequency is like a photo without focus. The details are lost.

@High_Fidelity said:

High frequencies take much less power to amplify. The transducer excursion is microscopic. Low frequency requires much more power to move the air that transmits sound to the ear. The transducer excursion is much greater. High frequency is directional, low frequency is not. That brings up another point. I have very little sense of direction with the hearing aids I have owned. As far as bandwidth, I’m talking flat response from about 6 to at least 12-kHz,

Yes, you are correct - but it doesn’t work like that - I’ll make this simple for you to understand.

If you tune a system/beam/whatever to a specific resonance it will resonate most freely at his resonance. You will have a primary resonance and then harmonics at double the frequency and multiples thereof. Look at the dB HL curve in terms of SPL and the amount of roll off at the HF (and LF) before you start thinking about it. What you think of as consistent levels of gain over several pitches ISN’T.

Take this a step further, hearing aids are mainly designed for SPEECH, therefore receivers (Look at the Knowles Tech bulletins, data-sheets and support notes ) are designed around the same principle. Most speech occurs in the 250Hz to 6Khz range, therefore the basic receiver design is a rising response to 1KHz with a damped sinusoid tail. This gives a response shape somewhat like a porcupine’s back, depending on the beam/reed resonance caused by the interaction of the magnets and coil in the balanced armature set-up.

Given your vast experience in this field, you’ll know that the area under the curve is the amount of power possible. Now, you can fart around with this area, but unless you increase the drive voltage you can’t increase it. Therefore, if you WANT a response that goes out to 20Khz you can (in theory) do it - however, we aren’t providing hearing aids for bats. In the process however you move the peak out of the sweet spot in the middle of the dB HL weigting and have a lower response overall to reproduce a load of Frequencies you could only just hear when you were 30.

Lets throw some more issues in - Hysteresis ? Drive rod weld fatigue? Reed stress? Diaphragm material failure? Just say Twenty Thousand times a second in your head and then apply that to a physical system with components that are measured in millimetres with tolerances in microns.

If you’ve got any more ideas on how to make things better let Knowles know.

Thanks for a much more technical explanation of hearing aid transducer function. It’s not all that different than a loudspeaker with the voice coil directly attached to cone or dome shaped diaphragm.

A bat can hear up to 200,000 Hz. A cat can hear up to 64,000 Hz and from the majority of information I have read working with audio equipment a human can hear up to 20,000 Hz, rolling off with age. As a kid, I remember hearing the horizontal sweep oscillator running in the family’s black and white TV set. That was 15,734 Hz.

In the first decade after World War II, high end consumer audio products frequency response went from 6,000 Hz to 20,000 Hz. Harry F, Olson designed curvilinear shaped cone speakers helped disperse high frequency much more efficiently. Resonance tuned speaker enclosures allowed big low frequency sound from small packages with amplifier power output as low as 3 to 10-watts.

A hearing aid is not trying to fill a 1000 cubic foot room with sound, only a fraction of an ear canal. Is it that outrageous for me to entertain the thought that maybe it could be done a little better?

I understand that only speech and device size is considered important. I wouldn’t want to miss a word of what most people have to say nowadays but my type of loss is not unusual and it is hearing loss. Maybe it is not as profound as other types of hearing loss and people with more serious loss have my empathy. I’m not surprised that my complaints have been dismissed.

The hearing aid industry has an opportunity here to assist people like me. If we are able to shell out 4 to 5 thousand dollars every 5-years on a pair of aids that really don’t address our specific problem, Imagine what we would pay for a pair that did.

One improvement I would suggest is the shape of the microphone openings. Those square cut little holes do not do a good job trying to pick up directional high frequencies. If the openings had more of a curvilinear shape, they might help reflect high frequencies into the microphone. If I position a glass or soda can near the openings, it reflects high frequencies into the opening and makes a huge improvement.

@High_Fidelity said:

A hearing aid is not trying to fill a 1000 cubic foot room with sound, only a fraction of an ear canal. Is it that outrageous for me to entertain the thought that maybe it could be done a little better?

What exactly do you think the R&D people do in these multi-million €$ businesses every day?

Yes, High_Fidelity I totally agree with you. I’ve been working on audio and digital signal processing for decades. The problem comes from the input or from the processing power, NOT from the output, since earphones can work at much higher freqs.

@High_Fidelity said:

Audio without high frequency is like a photo without focus. The details are lost.

I’ll steal this quote!

Thanks.

Don’t Panic! …

@High_Fidelity - did you ever find a solution to allow you to hear more higher frequencies?