[vox-tech] Linux sound recording

[Peter Jay Salzman]

On Tue 17 Jun 03,  8:36 AM, Henry House <hajhouse@houseag.com> said:
> On Tue, Jun 17, 2003 at 08:15:19AM -0700, Peter Jay Salzman wrote:
> > On Tue 17 Jun 03,  6:59 AM, Henry House <hajhouse@houseag.com> said:
> > > I am looking to do some sound recording on Linux. Specifically, I want to
> > > digitise some valuble old audiotapes before they or my tape player decay. So
> > > I think I need a sound card. Criteria:
> > > 
> > > * high quality analog-to-digital converter in stereo
> > > * input from tape deck via cable for said converter
> > > * Linux support, of course
> > > * Reasonable cost
> > > 
> > > Any recommendations?
> > 
> > yes.  i don't have an answer, but i know where you can get one.
> > 
> > 1. the linux audio quality howto.   i found this by accident.  it's not
> > a real howto, so it's not on tldp.org.  you'll have to google for it.
> > 
> > 2. the linux-audio-user mailing list.
> 
> Excellent! Both are to be found at http://www.linuxdj.com.o
 
interesting site.  dj == ?   the kernel hacker dave jones?

> The main two points seem to be:
> 
> 1. Get all analog signals as far away as possible from AC power and any PC
>    electronics.
 
transmission lines are good antennas, just as antennas by their very
nature must be good transmission lines.

> 2. Buy high-end hardware intended for recording, not gamer / comsumer
>    hardware.
 
yes!  i first started thinking about this only a few months ago.  in
fact, i just submitted the newest copy of the linux gamers' howto to
tldp.org, and said this very thing.   dunno why it didn't occur to me
sooner.

> Dumb newbie question: is a high signal-to-noise ratio (e.g., 100 dB) better
> than a low one?

i think you want a high signal to noise ratio.   signal is considered
good, noise is considered bad.   btw, human's can hear betwedn 1dB and
100dB.   a *really* noisy new york city subway train (like the IRT line
in brooklyn) is about 120dB.  this is considered beyond the threshhold
of pain.

decibels are on a logarithmic scale, meaning they're non-linear.   you
would think that 3 dB is three times as loud as 1 dB, but it's actually
ten times as loud.

decibels are units of power, but are used mostly for sound.  this is
because the human ear's sensitivity is roughly logarithmic.   sound
waves with power 1dB is roughly 10 times softer to a human than a sound
wave with a power of 3dB.

btw, there are different definitions for decibels, but the differences
are minor.  all definitions include a logarithm between two numbers you
want to compare.

in practical terms, the range between the softest sound we can hear to
the loudest sound we can hear without pain is roughly 12 orders of
magnitude, so to an engineer, it's convenient to use a unit of
measurement that's logarithmic, so they don't have to enter numbers like
124833.8742234 on their HP calculators.   kind of like how engineers use
those stupid logarithmic bode plots that they learn in basic EE classes
(but never use again) for transfer functions.

of course, to a physicist, decibels are inconvenient, because to us,
everything has a power of "P".    ;-)

pete

-- 
GPG Instructions: http://www.dirac.org/linux/gpg
GPG Fingerprint: B9F1 6CF3 47C4 7CD8 D33E 70A9 A3B9 1945 67EA 951D