Besides the usual live versus Memorex stuff...
20 years ago I was in on a business trip in Asia, and the telephone system (Japan?) had a background residual noise which sounded like many time multiplexed voices. It had a discernible human-voice quality. How?
At a radio-telescope, they setup two large (10'?) dishes at maybe 100 yards distance, aimed at each other as a science demo for kids. I setup a portable radio having some bass output at the focal of one and listened at the focal of the other. No bass - gone like through a HP filter. Why?
20 years ago I was in on a business trip in Asia, and the telephone system (Japan?) had a background residual noise which sounded like many time multiplexed voices. It had a discernible human-voice quality. How?
At a radio-telescope, they setup two large (10'?) dishes at maybe 100 yards distance, aimed at each other as a science demo for kids. I setup a portable radio having some bass output at the focal of one and listened at the focal of the other. No bass - gone like through a HP filter. Why?
1) Could have been bleed through from other circuits. I've heard stuff like that also.
2) The 10 foot diameter dish would radiate more efficiently at frequencies higher than
the point where the diameter is equal to the wavelength, similar in behavior to a tweeter.
The frequency of a 10 foot wavelength is around 112Hz.
2) The 10 foot diameter dish would radiate more efficiently at frequencies higher than
the point where the diameter is equal to the wavelength, similar in behavior to a tweeter.
The frequency of a 10 foot wavelength is around 112Hz.
To add:
1) Long lines running in parallel results in capacitive coupling. You did hear human voices although with just enough privacy not to recognise who, what and where.
2) Hats off for rayma.
1) Long lines running in parallel results in capacitive coupling. You did hear human voices although with just enough privacy not to recognise who, what and where.
2) Hats off for rayma.
> 10'? dishes at maybe 100 yards distance
So 10 feet to 300 feet. 30:1 target cone. About a 3 degree angle.
At 1 wavelength (Rayma's 112Hz) the beamwidth is about 60-90 degrees. At 10 wavelengths, 1,120Hz, about 6 degrees. Most of the low sound misses. You have to go over 2,000Hz to get most of your sound in a 3 degree cone.
Unbolt a dish and bring it in to 30 feet, angle is 30 degrees and delivery is good down to 200Hz. (Of course 10' dishes 30' apart is somewhat silly. Two Dixie-cups and a string does as well with far less material.)
> many time multiplexed voices
Telephones usually ARE multiplexed. This started in the 1930s. Since 1990 the fashion is to garble to digital bits and reconstruct with very low error (crosstalk). But for a half century plus it was common for the residual "noise" on a busy trunk to be dozens or hundreds of voices multiplexed in various ways. You say this was circa 1999-- telephone systems in mature neighborhoods lag behind the leading edge of technical progress. My street is on some 1980 concentrator. Little background jabber because there have never been 100 connections and rarely over a dozen users at once. But similar old concentrators in busier neighborhoods jabbered and sometimes discrete shouts woud break through.
All of this may be worse when tarnish builds up in connectors encouraging alternate paths of leakage.
So 10 feet to 300 feet. 30:1 target cone. About a 3 degree angle.
At 1 wavelength (Rayma's 112Hz) the beamwidth is about 60-90 degrees. At 10 wavelengths, 1,120Hz, about 6 degrees. Most of the low sound misses. You have to go over 2,000Hz to get most of your sound in a 3 degree cone.
Unbolt a dish and bring it in to 30 feet, angle is 30 degrees and delivery is good down to 200Hz. (Of course 10' dishes 30' apart is somewhat silly. Two Dixie-cups and a string does as well with far less material.)
> many time multiplexed voices
Telephones usually ARE multiplexed. This started in the 1930s. Since 1990 the fashion is to garble to digital bits and reconstruct with very low error (crosstalk). But for a half century plus it was common for the residual "noise" on a busy trunk to be dozens or hundreds of voices multiplexed in various ways. You say this was circa 1999-- telephone systems in mature neighborhoods lag behind the leading edge of technical progress. My street is on some 1980 concentrator. Little background jabber because there have never been 100 connections and rarely over a dozen users at once. But similar old concentrators in busier neighborhoods jabbered and sometimes discrete shouts woud break through.
All of this may be worse when tarnish builds up in connectors encouraging alternate paths of leakage.
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Electronic voice phenomenon - Wikipedia
"Auditory pareidolia is a situation created when the brain incorrectly interprets random patterns as being familiar patterns.[39] In the case of EVP it could result in an observer interpreting random noise on an audio recording as being the familiar sound of a human voice."
Electronic voice phenomena came up in my current bedtime book, which is referenced in the Wikipedia article:
"In Pattern Recognition, a 2003 novel by William Gibson, the main character's mother tries to convince her that her father is communicating with her from recordings after his death/disappearance in the September 11, 2001 attacks.'"
Whenever any of us hear, or see, or experience something fully unknown...become that scientist! Evidence, proof, some facts...of any and all you can muster.
See something in the sky, a UFO?...if it's just the three of you?...got cameras on your phones...all three of you take different positions, triangulate the image on video, then one could make triangulation composites...making a 3D rendering. We virtually will never have devices to register the likes of infrared, ultraviolet, RF, or any other data outside our own senses (maybe a thermal camera?)...don't grab someone else to experience it, that person has no more "senses" than you do, grab your devices & theirs as well.
---------------------------------------------------------------------------Rick..........
See something in the sky, a UFO?...if it's just the three of you?...got cameras on your phones...all three of you take different positions, triangulate the image on video, then one could make triangulation composites...making a 3D rendering. We virtually will never have devices to register the likes of infrared, ultraviolet, RF, or any other data outside our own senses (maybe a thermal camera?)...don't grab someone else to experience it, that person has no more "senses" than you do, grab your devices & theirs as well.
---------------------------------------------------------------------------Rick..........
I never knew that about how parabolic dishes worked with regards to frequency. Unsure of what I was expecting to hear at the time - probably the exact same sound as if my nose was a few inches from the speaker. It just surprised me, as I recall. I noted someone is building a "parabolic speaker" and I guess for practical indoor dimensions, it's not going to radiate much low end - if they're going to construct it like a dish antenna.
I wonder what would happen if you took a 30" round parabolic dish, moved it slightly with a VC and at the same time pointed a FR speaker into it at the focal point? Maybe a terrible way to make a speaker...
The telephone background noise sounded as if it was made of 5 ms segments of random human voice "samples" - in another language - all strung together making a continuous sound. I wasnt particularly looking for the effect, just something I happened to notice in the sound as having a human voice quality - somehow.
I've heard crosstalk on "old fashion" telephone lines within the same house wiring - seemed to be non-linear too; only the loud passages (uproarious laughter) would leak through. Maybe from those oxidized connections along with a good long run out to the pole.
I wonder what would happen if you took a 30" round parabolic dish, moved it slightly with a VC and at the same time pointed a FR speaker into it at the focal point? Maybe a terrible way to make a speaker...
The telephone background noise sounded as if it was made of 5 ms segments of random human voice "samples" - in another language - all strung together making a continuous sound. I wasnt particularly looking for the effect, just something I happened to notice in the sound as having a human voice quality - somehow.
I've heard crosstalk on "old fashion" telephone lines within the same house wiring - seemed to be non-linear too; only the loud passages (uproarious laughter) would leak through. Maybe from those oxidized connections along with a good long run out to the pole.
When I was in high school, I'd met a guy giving an audio demo who was a Hammond organ tech that built electronic music signal processing modules, circa mid 1970's. He had a big red beard, a wife and kids - and an ARP 2600 in his house - he was cool. I was supposed to help him out with making a phase shifter out of CD4049s, biased as linear amplifiers - the design never worked, however his common 741 op-amp based design did.
He'd lent me his finished ring-modulator (in a standard 19" 1U format) to which I connected one channel to an electric piano. The modulating input I connected to the output of the analog phase shifter, which I assume did something like V(t)*V(t-t0). I recall ascending notes played produced descending harmonics - and vice versa. Unlike other "ring-modulator" effects using a fixed frequency carrier, I recall these sounded musically "pretty".
Another thing I've heard and to this day have no idea how it came about. I've never replicated that sound or moment. The piano was a Whurlitzer electric at Niskayuna high school. Probably a common sound effect used by "the Police" guitarist for years, FAIK...
He'd lent me his finished ring-modulator (in a standard 19" 1U format) to which I connected one channel to an electric piano. The modulating input I connected to the output of the analog phase shifter, which I assume did something like V(t)*V(t-t0). I recall ascending notes played produced descending harmonics - and vice versa. Unlike other "ring-modulator" effects using a fixed frequency carrier, I recall these sounded musically "pretty".
Another thing I've heard and to this day have no idea how it came about. I've never replicated that sound or moment. The piano was a Whurlitzer electric at Niskayuna high school. Probably a common sound effect used by "the Police" guitarist for years, FAIK...
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