Is it possible to determine whether a phone call is local or long distance by analyzing the audio?

Brian: That was my concern (minus the specific numeric frequency, of which I am clueless) as well.

See below Jeff's post. Maybe the residuals that he mentions contain some of the info that I need?

Regards,

-Ramon

===============================

Yes, but I'm not going to get involved in a conspiracy theory resurrection.

In the 1970's all long lines telephony was analog. There were channel bank filters and mixers that upconverted base band audio to higher frequencies for transmission, and back down at the destination. Also known as FDM (frequency division multiplex:

The conversion process is not perfect and it is possible to see mixes and intermodulation products of the carrier and local oscillator frequencies of this up/down conversion process on the resultant audio[1]. There was also about a 1 to 5 Hertz Bode frequency shift introduced to prevent feedback and oscillation. You can't hear the beatnotes and frequency shift, but you can see them with PC based spectrum analysis. I suggest:

or better yet Spectrum Lab:

You will need to look at the "blank" spaces between the words, where there is no voices or background noises to muddle the display. You're looking for continuous carriers, buried well under the voices.

Autocorrelation:

is a big help for seeing these tones by removing the audio and background rubbish.

Interpreting the residual tones, and separating them from recording artifacts, is going to be difficult. You'll need to find someone with experience in 1970's telco muxes as well as some clue as to where these recording have been, whether they were converted from previous recordings, and possibly what equipment was used. You'll also need to know which CO handled the call, which will point to which carrier handled the call (AT&T, GT&E, ITT, etc), and then what brand and model of carrier equipment might have been used. That's not going to be easy and will probably be a huge time burn for little benefit.

Hopefully, I've given you enough hints to get started. You're on your own. Don't bother sending me email as I won't help.

[1] I still do some of this looking for residual PL/DCS and control tones on stuck FM land mobile and public safety transmitters to identify the culprits. Since the frequency of operation is known, that limits the likely culprits to known licencees and a known list of equipment. However, the introduction of digital radios has made this technique both too difficult and no longer necessary due to built in transmitter ID.

Even at 16 bit 44.1 kHz sampling ( which is pretty mild these days ) it'll be fine. -96dB digital noise floor, 20-21KHz bandwidth.

--
Les Cargill

For the audio that you can hear, a WAV file, which is uncompressed, will catch everything that you could hear on the tape in the range of what a human can hear over maybe a dynamic range of maybe 60dB (my guess). The 20-20KHz frequency range is somewhat of a crap shoot as the upper end is often -10 to -30 dB down and the response curve is anything but flat. The typical 44 or 48 KHz WAV file digitization is far better than the cassette tape. Just make sure the recording is not clipping on peaks, compressed in any way (no MP3), not noise reduced (Dolby), and not "enhanced" by the WAV recording software. While these may make the audible part of the recording easier on the ears, it also causes low level artifacts to disappear forever. Such "enhancements" can always be done on the WAV file later. I'm not sure if a FLAC file is appropriate.

Conspiracy theories are not going to save the earth. More likely, the information is going to be part of some media circus, of which I want no part.

Yeah, sorta. The upper limit on a cassette recording is about 20 KHz. Digitizing much over the Shannon limit (2*20KHz = 40 KHz) isn't going to magically deliver sounds on the tape that were over about 20 KHz. However, what a higher frequency will do is prevent the 40 KHz digitization rate from creating aliasing frequencies that will appear below 20 KHz and mangle the digitized copy. 96 KHz 24 bit and 192 KHz

24 bit digitizers are cheap and common. Use one.

The problem for this recording is NOT the electronic copy, which is potentially of far better quality than the original cassette tape. The problem is that the cassette tape is by its very nature a piece of disgusting technology that should have died before it was inflicted on the general public. It would be difficult to design something of lesser quality. Even 8 track was better. When you digitize the audio (hopefully not using a microphone like the CNN reporter), it will probably not be worse than the original cassette, but also not any better. In other words a close to perfect reproduction.

The next step would probably be to "clean up" or "enhance" the digitized WAV file recording. Over simplified, you can emphasize any part of the recording, at the expense of other parts of the recording, in either the frequency domain, time domain, or amplitude range. However, there's no free lunch. To make low level noises more audible, you have to limit, clip, chop, compress, or otherwise reduce the high level sounds. To bring out sounds with a limited frequency range, you have to reduce the level of other sounds outside this range. To bring up the level of gunshots and echos, you'll need to reduce other loud noises. Anyway, welcome to forensic acoustic analysis.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

On a sunny day (Tue, 17 Mar 2015 20:45:06 -0700) it happened Jeff Liebermann wrote in :

From a forensic POV I would only want the original tape. The rest sounds like 100 % bull to me.

:-)

You can do things with that tape, as Mr Liebermann pointed out earlier, like looking for bias (changes) by for example playing at slower tape speed in some setup, in a specialized setup. All the media crap and CNN talk is complete nonsense. They just need to fill air time, something incredibly easy if you assume some grey cells in the audience [1], but rather difficult if you want to entertain apes [2].

[1] Open university. [2] CNNs target audience.

Quote me.

You are very uninformed, esteemed Jeff...

How can a person with the most beautiful music in the whole web can be so cranky!!???

(a) The media is not interested in the JFK case. See how they mention it in a rush in all the videoclips, and that's OKAY!

Even if they were:

(b) This is *not* about Kennedy. See these two videos:

[Fast forward to Minute 3:00]

(c) It will end up in my poor man's "web site" since I cannot afford a real one. It will not go further, rest assured. Geeky stuff is not news, unless you land a probe in Mars. You are specially invited to take a look at the *two* folders named "Learning Material", and any suggestion of papers (specially readable by those of us without PhDs!) are welcome.

This is about the insult of Mr. O'Reilly to the work continuing done by the likes of me [and those co-inventing the Internet with Al Gore (*)] and all participants in the sci.electronics forums.

-Ramon

(*) Let the wisecracks begin.

Hardly. I have Google to find all my answers. What more could I want?

Easy. Music is my escape from reality. Without music, I would really be a classic curmudgeon.

Sorry. I missed the change in topic somewhere upstream.

Everyone lies, but that's ok because nobody listens.

Have you ever been quoted by the press? I have a few times. Every time, what is printed is a total distortion of what I said or what happened, usually to fit someones agenda. I suppose it might be possible to report the news accurately, but it would bore the audience, irritated the sponsors, and probably vilify the owners. What people want is entertainment from literally everything they read, watch, or do. If it's not fun, find something else. Much of entertainment is fantasy. The only question for the press is how much fantasy.

If you want examples, just watch any "action" movie and see how many gross violations of basic physics you can see. Long ago, I went to a movie theater only to find that it had been taken over the Naval Postgraduate Skool to watch the 1972 version of the Poseidon Adventure. The students were expected to catch and detail the numerous distortions of hydraulics, maritime technology, buoyancy, physics, etc. There were plenty. It might have been nice to correct all those mistakes, but then, the movie would be terminally boring. Todays news has more in common with movie style "creativity" than with reality.

I pay 1and1.com about $10/month for hosting my junk and some of my friends junk. I suspect you can afford that.

Yep. It's boring. Making electronics exciting is a major challenge for the future or we may not have any engineers.

Interesting stuff, but getting involved would burn too much time. Sorry.

Also, this is nothing new. There is specialized software for removing vocals from music to produce Karaoke CD's available. You can sorta do it with Audacity: With a stereo recording, I can also filter by differential audio delay to remove or enhance voices or instruments.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

Yes, newspapers and TV. *HAD* my 15 minutes of fame. That is the cool thing about being from a relatively small, underdeveloped country: It is a heck of a lot easier to reach some degree of recognition than in the US or any developed, larger country.

Would you prefer:

(a) Techie Stuff?

(b) Civil and Military Unrest, assassination threats?

I am cursed with being involved in both the technical infrastructure, founding newsgroups (not to mention the first Arab Spring, 20 years earlier) and with militant, activist content.

Let's start with (a).

My predecessor, head of the Venezuelan Internet was invited to meet with his peers: the head of every country's Internet, in sunny Hawaii, all expenses paid. Meanwhile, the country's Internet service was shut down (another first and last!) for lack of payment. The bean counters in the Caracas treasury had no idea for what the hell was that invoice. It spent one year in red tape (The John von Neumann ISP had given us some time for free, to wet the appetite, but the freebie had expired).

But it digress: When this suntanned guy arrived back in Caracas, after his share of pina coladas and Hawaiian shirts, he had already been fired.

Every university (the important ones) submitted a trio of candidates, for Luis' replacement. I was in Cambridge when I received a call from the Minister of Science and Technology:

"Ramon, in every single one of the university proposed candidates, yours name is the first one. There is unanimity. Congratulations. However, if you are not here in Caracas next week, I will appoint the second runner".

Meanwhile there were headlines in the national press:

"La red de las mil tormentas espera por Ramon Herrera" [It rhymes in Spanish]

"The network of the 1,000 storms awaits for Ramon Herrera".

As soon as I arrived was interviewed in a TV program. Hierarchy-wise, there was one officer between me and el Presidente.

For bloody stuff (b), see attachment.

In what year were you in the news? What was the context?

-Ramon

Can 1and1.com even approach Google's bandwidth?

I need lots of disk space (WAV files sampled at max rates) and bandwidth. Video, too. For example, I would like to have several revisions of the "Lancer" videoclip, with monotonically increasing quality.

Why that? Why not? (*) I consider it a cool example, that broaches my 2 passions. The contents is cool, for us JFK buffs, anyway. It is not too hard or too easy. With the current state of the art, it needs a lot of

*hand* work (careful visual erasure).

Have I said that I am obsessed with quality? A perfectionist?

Can they host all this?

I just got started filling it up.

-RFH

(*) "There are those who look at things the way they are, and ask why... I dream of things that never were, and ask why not?"

I don't know, don't have the numbers, don't know your requirements, and don't have the time to research or guess. 1and1 does unlimited bandwidth, same as some of the other providers. Google is probably cheaper. I vaguely recall my storage limit is 2 GBytes per account: I just checked my account and I'm half way there. Hmmm... looks like two downloads of my entire site by someone in Korea. This could be interesting.

What's that in Mega/Gigabytes?

A bigger trash can does not make a cleaner web site. Unfortunately, that applied to my disorganized sites.

I'm in the former category. I wonder why things are as screwed up as they seem. My background is in repair, service, redesign and damage control. Reverse engineering someone else's stupidity is all too common. Nobody will pay me to create the next big thing. Instead, I get to determine why things aren't working as someone had dreamt, and occasionally fix the problems. I do have some dreams of things to come, but they're not for public consumption.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558