Question re copying cassette tapes

[Christopher Cox]

On Thu, Feb 11, 2010 at 10:50 PM, William J Poser <wjposer at ldc.upenn.edu> wrote:
(SNIP)
> (c) use a lower sampling rate
>    If you use a rate of 22.05K, this gives you a savings of 50%
>    at little or no cost in quality. This applies only to pure speech data.
>    Some music may well contain higher frequency components of significance.

I'm not sure that I agree with this point entirely: using a sample
rate of 22,050 Hz should, as both Bill and Keola have pointed out, be
able to reproduce essentially the entire primary frequency range for
speech, from the low 'bass' fundamental frequencies to the upper end
of high-frequency frication.  In that sense, we're not losing anything
by recording language samples for phonetic analysis at this sample
rate, and can certainly save storage space by doing so; 22,050 Hz has
been recommended for a long time in phonetics, even finding its way
into popular textbooks on phonetic fieldwork (e.g. Ladefoged 2003, p.
26).

This doesn't mean that samples recorded at this rate necessarily sound
as good as higher-frequency recordings, though, as Keola mentioned.
Even though this sampling rate captures the essential frequency range
for speech (i.e. up to around 11KHz) , most people's hearing extends
well beyond that into the 20KHz range.  The lower sampling rate might
not incur distortions that would affect phonetic analysis, but there
is usually still an audible difference in quality between recordings
digitized at 44.1KHz versus those digitized at 22.05KHz, and likewise
for higher sampling rates.

I'm not sure that Ladefoged's recommendation of a 22,050 Hz sampling
rate was really made with reuse of recordings outside of phonetics in
mind.  For some other purposes, the 'aesthetic' sound quality of a
recording may be fairly important, maybe particularly if recordings
have some cultural, historical, or even just sentimental value.  If
22,050 Hz was all that was available, there'd certainly be no harm in
choosing it -- but it would seem a shame to make recordings of a lower
audio quality, just because they're all that's needed for instrumental
phonetics!

Anyway, that's just a thought.  For what it's worth, NINCH (2003),
Bartek & Kornbluh (2002), and the "Sound Directions" guide from
Indiana University all appear to recommend 96Khz / 24-bit WAV for
archival purposes:

http://www.nyu.edu/its/humanities//ninchguide/VII/
http://emeld.org/school/readingroom/bartek-paper.pdf
http://www.dlib.indiana.edu/projects/sounddirections/papersPresent/sd_bp_07.pdf

All the best,


-- 
Chris Cox
cdcox at ualberta.ca