Re: Audio / tinnitus

I've always been very sensitive to high frequencies and have noticed a
ringing in my ears in the last few months (tinnitus). It might be
caused or abetted by high frequencies emitted by my speakers and/or
monitor which emits a soft, high pitched whine from the back. The
high frequencies from the speakers are caused by a poor designed amp
that powers them. If I plug the speakers into my iMic which runs off
USB, instead of the headphone jack on the Mac Mini, its exactly the
same. So I know its not the Mac. Its the amp. There is a subtle
high frequency buzz that vanishes when the amp is turned off. Of
course if I turn the volume down its still there as it is the
background noise from the amplification. Its just not a low noise
design.

When I was younger I could hear annoying high frequency noises from some
CRT monitors and TVs. Some switch mode power supplies also produce
similar noises.

Yes - I know exactly the noises you speak of.

If the amplifier is the problem, perhaps a simply low pass filter (say a
suitable inductor in the speaker lead) would be sufficient to reduce the
high frequency components? If you need more than 6dB per octave (and you
may) then you start looking at second and higher order filters. If your
computer speakers have tweeters, it might be worth a quick inspection of
their crossover, with a view to a modification.

Actually one solution might be to just put some material over the
tweeters - like a very cotton or something to absorb the high
frequencies, then remove it when I want to listen to music or a movie.


















Or just get a decent amplifier.

You may also want to do a quick and dirty check of your hearing. There
are some nice Java based web pages that allow you to output anything
from about 10Hz to 22kHz (by 1 Hz increments) from your Mac audio. I
noticed my AudioEngine 5 speakers really do go to 22kHz (well, according
to an SPL meter - I couldn't hear anything much past 16 kHz). My regular
cheap *** Smith speakers have given up well before that. However for
ear testing I used Grado SR125 headphones direct from my iMac audio
output.

I tried using some RS-1's and I got to 14 or 15k. I thought that was
good until some kid next door could hear way beyond that. Youth is
wasted on the young...:)

I don't recall the specifications of the Mac mini audio, but most of the
Mac line output specifications are reasonably impressive (well, maybe
not for real audio enthusiasts, but probably better than anything I
could hope to hear). I am pretty sure they would not be leaking real
high frequency audio into the line out outside their specifications.
Maybe someone with ready access to an oscilloscope could help you check
that and your amplifier? Electronics lab at school perhaps?

The Mac is fine. Its definitely the lousy amp in my powered speakers.
The tweeters in the speakers are good enough to show it up though.
Now I just turn it off and have an old $5 computer speaker I use to
listen to alerts and talking. Works fine for now.

I'm going to try to pick up a decent mic though so I can check some of
this stuff out.
.