Since we are discussing microphones please look at my choice for hearing aid and comment.

pe to get these into hands of those that the VA cannot help.

has some on board amplifier which I expect will help with keeping noise und er control while providing a nice signal. It will turn on following amplif ier on wake-up. Frequency response is good enough.

input. I hope you like that your efforts may someday help veterans.

comments?

Do you envision some frequency-response shaping? I suppose you imagine a good level of usefulness to VETs without requiring a DSP and all that stuff?

--
 Thanks, 
    - Win

I will see what I can do with shaping response. I myself have -10dB at 1kH z and near -60dB at 4kHz. I have a LT Spice file using a few op-amps to co rrect this. I belong to a few military groups on Facebook with many having noise induced hearing loss NIHL. I will poll groups for more information concerning their hearing response. I would prefer a simple analog implemen tation, but I am not taking any design off the table. Once I get a few cur ves I will know if an analog implementation will fly.

Maybe the 10dB at 1kHz matters for normal activity, but I doubt a person who's hard of hearing would be unhappy missing out on 4kHz, if they could hear 1kHz better.

--
 Thanks, 
    - Win

My initial hearing loss was a notch at 4kHz. I had trouble hearing my wife. I was told that was where all the intelligence is in a female voice. I wont say anymore :)

How can that be, that's FOUR octaves above middle C. In the old days, phone lines didn't go up that high.

--
 Thanks, 
    - Win

great, a circuit to make speech less intelligible.

On 23.3.19 14:14, Yzordderrex wrote:

The filter response is on far too high frequencies to be good for speech. Besides, the filter configurations could be better, there are too many components for the response.

See LTSpice model:

Version 4 SHEET 1 1400 748 WIRE 288 64 272 64 WIRE 960 80 912 80 WIRE 128 112 32 112 WIRE 352 112 192 112 WIRE 704 144 592 144 WIRE 1056 144 784 144 WIRE 176 192 144 192 WIRE 352 192 352 112 WIRE 352 192 256 192 WIRE 848 224 800 224 WIRE 1056 224 1056 144 WIRE 1056 224 912 224 WIRE 288 272 288 64 WIRE -80 288 -128 288 WIRE -48 288 -80 288 WIRE 32 288 32 112 WIRE 32 288 16 288 WIRE 64 288 32 288 WIRE 144 288 144 192 WIRE 144 288 128 288 WIRE 256 288 144 288 WIRE 960 288 960 80 WIRE 352 304 352 192 WIRE 352 304 320 304 WIRE 416 304 352 304 WIRE 592 304 592 144 WIRE 592 304 560 304 WIRE 624 304 592 304 WIRE 736 304 704 304 WIRE 800 304 800 224 WIRE 800 304 736 304 WIRE 928 304 800 304 WIRE 32 320 32 288 WIRE 144 320 144 288 WIRE 256 320 224 320 WIRE 1056 320 1056 224 WIRE 1056 320 992 320 WIRE 1104 320 1056 320 WIRE 1232 320 1168 320 WIRE 1312 320 1232 320 WIRE 592 336 592 304 WIRE 736 336 736 304 WIRE 800 336 800 304 WIRE 928 336 896 336 WIRE 1232 352 1232 320 WIRE 32 448 32 400 WIRE 144 448 144 400 WIRE 224 448 224 320 WIRE 592 448 592 400 WIRE 736 448 736 416 WIRE 800 448 800 400 WIRE 896 448 896 336 WIRE 1232 448 1232 432 WIRE -80 480 -80 288 WIRE 528 512 464 512 WIRE 288 528 288 336 WIRE 288 528 272 528 WIRE 960 528 960 352 WIRE 960 528 944 528 WIRE 672 560 560 560 WIRE 464 576 464 512 WIRE 672 576 672 560 WIRE -80 640 -80 560 WIRE 464 688 464 656 WIRE 560 688 560 560 WIRE 560 688 464 688 WIRE 672 688 672 656 WIRE 752 688 672 688 WIRE 560 704 560 688 FLAG 32 448 0 FLAG 144 448 0 FLAG 224 448 0 FLAG 592 448 0 FLAG 736 448 0 FLAG 800 448 0 FLAG 896 448 0 FLAG 272 64 +15V IOPIN 272 64 In FLAG 912 80 +15V IOPIN 912 80 In FLAG 944 528 -15V IOPIN 944 528 In FLAG 272 528 -15V IOPIN 272 528 In FLAG 1232 448 0 FLAG 1312 320 Out IOPIN 1312 320 Out FLAG -128 288 In IOPIN -128 288 In FLAG 528 512 +15V IOPIN 528 512 Out FLAG 752 688 -15V IOPIN 752 688 Out FLAG 560 704 0 FLAG -80 640 0 SYMBOL Opamps/LT1124 288 240 R0 SYMATTR InstName U1 SYMBOL Opamps/LT1124 960 256 R0 SYMATTR InstName U2 SYMBOL res 128 304 R0 SYMATTR InstName R2 SYMATTR Value 100k SYMBOL res 16 304 R0 SYMATTR InstName R1 SYMATTR Value 120k SYMBOL res 272 176 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R3 SYMATTR Value 470k SYMBOL res 576 288 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R4 SYMATTR Value 8.2k SYMBOL cap 128 272 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C2 SYMATTR Value 2.2n SYMBOL cap 16 272 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C1 SYMATTR Value 2.2n SYMBOL cap 192 96 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C3 SYMATTR Value 150p SYMBOL cap 480 288 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C6 SYMATTR Value 100n SYMBOL res 720 288 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R5 SYMATTR Value 6.8k SYMBOL res 752 432 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R6 SYMATTR Value 33k SYMBOL cap 576 336 R0 SYMATTR InstName C7 SYMATTR Value 560p SYMBOL cap 784 336 R0 SYMATTR InstName C8 SYMATTR Value 2.2n SYMBOL cap 912 208 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C11 SYMATTR Value 150p SYMBOL res 800 128 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R7 SYMATTR Value 8.2k SYMBOL res 1216 336 R0 SYMATTR InstName R8 SYMATTR Value 47k SYMBOL cap 1168 304 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C12

SYMBOL voltage 464 560 R0 SYMATTR InstName V1 SYMATTR Value 15V SYMBOL voltage 672 560 R0 SYMATTR InstName V2 SYMATTR Value 15V SYMBOL voltage -80 464 R0 SYMATTR InstName V3 SYMATTR Value SINE(0 1.0) SYMATTR Value2 AC 1.0 TEXT 48 664 Left 2 !.ac oct 8 10 1e6

--

-TV

That's a strange looking topology.. a little like a Sallen-Key (VCVS) Thanks for spicing it.

George H.

What puzzles me are the components across the virtual grounds (opamp - input to ground). They should do nothing.

A good speech filter should have a high-pass with

2-3 poles to 300 Hz and one pole to 1200 - 1500 Hz, and low-pass starting at 3 kHz.

A couple of dB of peak clipping before the low-pass can also help.

--

-TV

Huh, I missed the opamp inputs signs.. It's an inverting VCVS.. sort of.

Maybe that's the 't' part in the Speetch Filter. :^)

George h.

Are you sure it wasn't 400Hz? That would mess up a female voice.

4kHz wouldn't make much difference. Male voice fundamentals are mainly in the 80-200Hz band and female voices in the 150-300Hz band with a few harmonics on top of that.

F6 at 1400Hz is about as high a note as the very best soprano opera

POTS phone lines used to only bother to carry frequencies 300-3300Hz and as a intelligible speech channel that was pretty well acceptable.

Loss of high frequencies makes it harder to recognise silibants. See:

--
Regards, 
Martin Brown

pe to get these into hands of those that the VA cannot help.

has some on board amplifier which I expect will help with keeping noise und er control while providing a nice signal. It will turn on following amplif ier on wake-up. Frequency response is good enough.

input. I hope you like that your efforts may someday help veterans.

I cannot get LT file to run. Am I supposed to copy text into a notepad fil e and then rename file.asc? Help. And thank you for creating the file.

hope to get these into hands of those that the VA cannot help.

t has some on board amplifier which I expect will help with keeping noise u nder control while providing a nice signal. It will turn on following ampl ifier on wake-up. Frequency response is good enough.

or input. I hope you like that your efforts may someday help veterans.

ile and then rename file.asc? Help. And thank you for creating the file.

I get error "Multiple instances of flag"