[jason]

I recorded the NPR feed for the State of the Union address tonight.
There's an interesting "hole" in the spectrum display that I cannot
explain. (I looked at some other audio feeds and saw the same thing.) I
presume mp3 compression is at work here - you can see black (no audio)
specks throughout the spectral display, but the hole is intriguing. Any
guesses?

http://dl.dropbox.com/u/36527603/SOtU.tif

[[email protected]]

NONE of my mp3s have a notch like that! Some are shelved off above 16kHz though - but I don't hear that high anyhow.

That bandwidth must be used for something.

[Frank Stearns]

Jason writes:

I recorded the NPR feed for the State of the Union address tonight.
There's an interesting "hole" in the spectrum display that I cannot
explain. (I looked at some other audio feeds and saw the same thing.) I
presume mp3 compression is at work here - you can see black (no audio)
specks throughout the spectral display, but the hole is intriguing. Any
guesses?


"Truth" band missing? (Apologies to the politically sensitive, but the setup was
soooo perfect I could not resist.)

But seriously, interesting problem. As you say, data compression artifact. More
interesting question is "why" and "where" this happened....

Frank
Mobile Audio
--

[Tobiah]

On 02/12/2013 10:23 PM, Frank Stearns wrote:
Jason writes:

I recorded the NPR feed for the State of the Union address tonight.
There's an interesting "hole" in the spectrum display that I cannot
explain. (I looked at some other audio feeds and saw the same thing.) I
presume mp3 compression is at work here - you can see black (no audio)
specks throughout the spectral display, but the hole is intriguing. Any
guesses?


"Truth" band missing? (Apologies to the politically sensitive, but the setup was
soooo perfect I could not resist.)

That's why when you look at the plot of the Rubio's reply,
you see nothing at all )

[Tobiah]

On 02/13/2013 09:30 AM, Tobiah wrote:
On 02/12/2013 10:23 PM, Frank Stearns wrote:
Jason writes:

I recorded the NPR feed for the State of the Union address tonight.
There's an interesting "hole" in the spectrum display that I cannot
explain. (I looked at some other audio feeds and saw the same thing.) I
presume mp3 compression is at work here - you can see black (no audio)
specks throughout the spectral display, but the hole is intriguing. Any
guesses?


"Truth" band missing? (Apologies to the politically sensitive, but the setup was
soooo perfect I could not resist.)

That's why when you look at the plot of the Rubio's reply,
you see nothing at all )

Hmm... that face came out as a sad one in my email client. It
was supposed the be the silly one with the comical agape mouth,
showing insincerity and levity.

[[email protected]]

NPR uses MP2 for their transmission to stations, I believe, but that shouldn't be the reason for that gap...

[John Williamson]

wrote:
NPR uses MP2 for their transmission to stations, I believe, but that shouldn't be the reason for that gap...

Could someone have notched out interference from something? Maye a CRT
teleprompter line scan coil?

--
Tciao for Now!

John.

[Scott Dorsey]

John Williamson wrote:
wrote:
NPR uses MP2 for their transmission to stations, I believe, but that shouldn't be the reason for that gap...

Could someone have notched out interference from something? Maye a CRT
teleprompter line scan coil?

That was my first thought, but it's too low. 10-12 KC? Very weird place
to cut..... I'd be curious what the story is too.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Mark]

On Feb 13, 3:04*pm, (Scott Dorsey) wrote:
John Williamson wrote:

wrote:
NPR uses MP2 for their transmission to stations, I believe, but that shouldn't be the reason for that gap...

Could someone have notched out interference from something? Maye a CRT
teleprompter line scan coil?

That was my first thought, but it's too low. *10-12 KC? *Very weird place
to cut..... I'd be curious what the story is too.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

to the OP..

was the NPR recording from an FM radio?

or from where?

FM radio with stereo MPX has a pilot tone at 19kHz and many receivers
will notch that out...

is there perhaps a frequency scaling problem in the FFT setup,

are you sure the null is at 11 kHz? and not 19kHz?

Mark

[[email protected]]

Mark:

I'm sure even our last president can distinguish a notch or peak at 11kHz from one at 19kHz, even on a log scale.

[Trevor]

wrote in message
...
I'm sure even our last president can distinguish a notch or peak at 11kHz
from one at 19kHz, even on a log scale.

I'm pretty sure GWB wouldn't know what *any* of that meant.

Trevor.

[jason]

On Thu, 14 Feb 2013 06:40:26 -0800 (PST) "Mark"
wrote in article 5093b5c2-6458-44d4-ab32-1d7a81f0f736
@n6g2000vbf.googlegroups.com

...

to the OP..

was the NPR recording from an FM radio?

or from where?

FM radio with stereo MPX has a pilot tone at 19kHz and many receivers
will notch that out...

is there perhaps a frequency scaling problem in the FFT setup,

are you sure the null is at 11 kHz? and not 19kHz?

Mark

It was recorded from a computer feed, not an FM radio.

I'd wondered if there was some kind of in-band signalling going on
but I doubt it in this day & age. (I remember hearing little chirps
and tweets during CBS radio news broadcasts a few years ago, but
I no longer do.)

[[email protected]]

It's known that notches in that range give the illusion of height, as it mimics the HRTF curves for elevation. Discuss .....


Bob

[Trevor]

"Jeff Henig" wrote in message
...
"Trevor" wrote:
wrote in message
...
I'm sure even our last president can distinguish a notch or peak at
11kHz
from one at 19kHz, even on a log scale.

I'm pretty sure GWB wouldn't know what *any* of that meant.


I'm doubting very many political figures would.

And if BHO knows as much about audio as he does about economics, I'd be
surprised if he knows what a waveform is.


Agreed, but that would still put him streets ahead of GWB. He was
entertaining in a cringeworthy way though I guess, but I'm still glad he was
yours. Ours are bad enough, but not *that* bad :-)

Trevor.

[[email protected]]

Trevor, et al:

Anywhoooooo.... The mystery of the 11-12kHz notch remainzzzz. Not that I would be too awares of it - my hearing starts to roll off above 11k.

[Frank Stearns]

Jeff Henig writes:

"Trevor" wrote:
wrote in message
...
I'm sure even our last president can distinguish a notch or peak at 11kHz
from one at 19kHz, even on a log scale.

I'm pretty sure GWB wouldn't know what *any* of that meant.

Trevor.

I'm doubting very many political figures would.

And if BHO knows as much about audio as he does about economics, I'd be
surprised if he knows what a waveform is.

Chuckle.

If BHO knew as much about audio as he does about econ, we'd have Alice In Wonderland
Audio...

And/Or, we'd centralize production and mix: you would always use the EXACT SAME EQ
and compression on your lead vocal track, regardless of genre or voice.

And/Or, "The Affordable Microphone Act": Those of you with U47s, 251s, or any other
classic microphone with a high market value (regardless of actual merit) would
surrender that micrphone to the government, wherein the government would issue
everyone (including you) two SM57s and two SM58s (or maybe just one of each when the
shortages start). But honest, this legislation would really really help microphone
inequity.

And! And! It'd bring down the price of those classic mics to maybe just a little
more than the 57s! Honest! (Well, yeah, I suppose so, as The Affordable Microphone
Act might well drive UP the price of an SM57 to $14,000.)


And/Or, "The Benghazi Multitrack," where you were doing a rather dangerous film
production and you really did need 100 tracks for dialog, fx, and music, but all you
were allowed was an Ampex A440-4. A noble machine making a noble effort, but hugely
overwhelmed by the job (and you only had ONE 2500' real of tape with no take-up
reel, facts you'd been shouting back to the main office for months).

More stinging still, everything you needed was just a room away, but Studio
management wouldn't let you use it. In addition, several of your counterparts from
other departments in the studio were begging to be allowed to go help. But
management didn't want to look bad because they'd not made those assignments
earlier, as they should have, even though the script (guessed at for months; it was
another classic blockbuster from the same old bunch) obviously called for the extra
gear. But, studio management was heading out to the golf course. Don't bother them.


And/Or, "The Green Audio Act": Solar-powered gear for night-time sessions, when a
lot of musicians like to work. Oh, and BTW, no batteries allowed because of the
mining and smelting of heavy metals. Solar powered recorders don't work at night? No
matter; SOME insider convinced the goverment that such machines would work and got
extremely rich on the $500M "loan", the monument to which stands empty along a
Bay-area freeway.


You get the idea. And you don't even need to go back to GWB any more. It's soooo
target rich right now, really rich, just in the past few years.

Everybody chuckle. Those whose ears might be steaming chuckle AND take a breath.
It's all in good fun. w

Frank
Mobile Audio
--

[hank alrich]

Jeff Henig wrote:

"Trevor" wrote:
wrote in message
...
I'm sure even our last president can distinguish a notch or peak at 11kHz
from one at 19kHz, even on a log scale.

I'm pretty sure GWB wouldn't know what *any* of that meant.

Trevor.

I'm doubting very many political figures would.

And if BHO knows as much about audio as he does about economics, I'd be
surprised if he knows what a waveform is.

As if the laymen know ****all about economics. This, to me, is one of
the most laughable aspects of contemporary society. Everybody thinks
they know a lot about everything. Preposterous.

--
shut up and play your guitar * http://hankalrich.com/
http://hankandshaidrimusic.com/
http://www.youtube.com/walkinaymusic