Measuring Noise Levels (S/N)

[Bob Zimmer]

At 09:15 AM 3/21/97 -0000, you wrote:
>There really are only about 3 instruments made capable of accurately making
these measurements. The most widely used (by far) is an Audio Precision
Model 1. It is a true 18bit (100dB) device. This generates all of the SNR
plots you see in magazines like Stereophile. There is a new Model 2 out that
is 22bit (128db). The downside is that these are $10K boxes. I'm trying to
find a used Model 1 for $4500.
>
>For 16bit measurements (say 80dB) stuff, there is a Stanford Research FFT
analyzer for $1000 that does a nice job. There is an old HP DSP-based box
(can't remember the number offhand) that you can get used for around $1300
that is like the SR box, few more bells.
>
>The gist of the problem is that if you are over 35 years old, your high
frequency rolloff in your ears is about 14KHz and so you are correct about
not hearing anything. Also, it will greatly depend on your amp&speakers if
it is audible.
>
>Paul Schreiber
>Synthesis Technology
>

Whew!  That's too expensive to bother with!  I was hoping that there was
some way of doing it with a scope!

I think that I'll just trust my ears.

I am over 40 and know that my hearing has rolled off, but according to a VCO
and my frequency counter, I can still hear to about 17.5K or so.  I always
test with decent headphones to eliminate room noise!

  >=== Bob Zimmer -- Philadelphia PA ===<
  >=== bzimmer at voicenet.com          ===<