[Audio Empire]

On Wed, 20 Apr 2011 07:13:16 -0700, Arny Krueger wrote
(in article ):

"Edmund" wrote in message

Hi Guys,

Since I now finally have a HD player I like to buy HD
material. There is a possibility to buy HD tracks on
line. However when I open such a file with "Audacity" I
don't SEE any frequency above 20 kHz, but I must admit I
did not totally analyze this data I just looked at it in the
graphics of Audacity. But I still wonder if any of these
tracks actually contains frequencies above 20 kHz.
What do you guys make of this?

Many so-called hi definition recordings are actually 24/96 or 24/192
transcriptions of analog tapes and 16/44 or 16/48 masters. Analog tapes were
ususally made at 15 ips which pretty well eliminates response above 25-30
KHz.

Actually, it's difficult to maintain even a pro 15 ips analog tape recorder
to much above 15 kHz. Self erasure, poor head contact at ultra-short
wavelengths all make analog tape "iffy" at much above 15 khz. Back in analog
days, most studios only maintained their tape decks to 15Khz. More than that
took too long and wasn't practical. Before I recorded the SF Symphony back in
the 1970's I would carefully align both Otari MX5050s for head azimuth, bias,
frequency response, and Dolby 'A' level AFTER I set up the equipment (the
tape recorder was not moved after that). I never tried to get response beyond
15 Khz, but I scrupulously maintained the recorders to that level.

Any of you have a source for HD which has music
information above 20kHz?

Not really. Let's say that the recording was made at 24 or 32- bit and 192
KHz (or perhaps DSD). The recording equipment might have that kind of
bandwidth, but I'll guarantee that the microphones used don't. Most
condenser mikes fall-off like a rock above the resonant frequency of their
diaphragms - and that is usually 16 -18 Khz. Not much there above those
frequencies. Doesn't matter, though. You likely wouldn't be able to hear it
anyway.

As Jwvm correctly points out, nature abhors the creating of true hi def
recordings. His list of reasons is good and relevant.

Let me make clear that I don't want to start whether or
not higher frequencies are audible, only that HD music
should have recorded higher frequencies in the first
place.

Why would it? A chain is only as strong as its weakest length. In the case of
recording, as elsewhere in audio, the weakest length is always the
transducers - speakers, phono cartridges, microphones. In this case it's
microphones.

I agree that it is very nice when so-called hi def tracks are actually hi
def! ;-)

The hi-def doesn't refer to recordings filled with extraneous and inaudible
ultra-high-frequency information, it refers to the fact that the bandwidth of
the medium is wide enough that only gentle slope filters, located high above
the highest audible frequency, need to be employed on either end of the the
chain (recording and playback) to satisfy Nyquist. Many insist that this
sounds better. Certainly, recording information that only small dogs can hear
is of no use to most humans in and of itself. The advantage (if any) is in
the process of recording and playing back with a very high sampling rate, not
the information that such a sampling rate is capable of quantizing. Hint, if
any part of high-resolution recording is beneficial, its the word length (24
or 32-bits) not the sampling rate.