Re: [MLUG - DISCUSSION] Teen Repellent

["Mark Rages" <EMAIL:PROTECTED>]

On 6/7/06, Mike Miller <EMAIL:PROTECTED> wrote:
> On Wed, 7 Jun 2006, Jerry Gamblin wrote:
>
> > You could try it on this webpage I think:
> >
> > http://www.phys.unsw.edu.au/~jw/hearing.html
>
> That is a pretty cool web page, but there is a major difficulty with using
> it to measure your hearing, even informally, because your speakers might
> cut off at the low and high ends so that they don't even make the sound
> you are trying to hear.
>
> I can't hear anything at 60 Hz on my system, nor at 16 KHz.  This doesn't
> make sense to me though because the low A on my guitar is at 110 Hz, so
> the low A on a bass is at 55 Hz and I can hear that just fine.  I'm sure
> the overtones help me to hear it, but still.  There's also the famous "60
> cycle hum" that I can hear just fine.
>
> That is a very cool page though.
>
> Mike

You need a physically large driver to make sound at 60 Hz.  Nowdays,
it's more common to put a rise in the bass response at about 150Hz,
and cut off entirely around 80Hz, and let the ear/brain fill in the
lower two octaves.  This is what all the dinky "satellite / sub"
combos do. I think Bose was first to popularize this acoustic hack.
But when you hear a system that accurately makes the lower bass, you
feel it as much as hear it.

All this to say, I'm sure your computer speakers aren't producing much
output at 60Hz.

Re: 60 cycle hum.  In electronics, the sine wave is frequently
rectified into a 120Hz wave with a lot of overtones.  A pure 60Hz size
wave has a deep, pure sound like an organ pedal.  The powerline buzz
that you hear when you touch your dinger to a live guitar cord is
almost entirely overtones.

Regards,
Mark
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