This collection of early BBC training guides and manuals might be of reference interest for those using recording gear or techniques with roots in the 1950’s onwards:

https://www.bbceng.info/Books/books.htm

https://www.bbceng.info/Books/HQ%20S...production.pdf

There be gold in those docs.

I still have a hard copy from Wood Norton.

Shame no one pays any attention to the craft these days.

I had the BBC training manuals from the mid-60s*. I got to look through those to see what's different, thank you for posting the link.

*until someone of GS talked me into shipping them to him

great post and amazing info. back when actual engineers wrote audio books.

Wow, this is a gold mine. Great find!

Regards, C.

V fun! Thanks Ray!

Really great resource! Thank you.

Thanks.

Back to school.




EDIT:

Haha, I just skipped through the book on the second link and my eye caught this section immediately:

"4 COMBINATION TONES

When a number of frequencies are sounding simultaneously, the
brain receives the impression that additional frequencies are
present. This effect is inherent in the mechanical action of the ear,
and makes analysis of complex sounds in terms of the sounds actually
imagined in the brain exceedingly difficult. One of the " extra "
sounds created in this way, when two pure tones are being sounded
together, is at a frequency which is the difference between the two
real frequencies. For example, if tones at 1,000 c/s and goo c/s
are present, the hearer feels that I oo c/s (I ,000 -900) is also sounding.
2
6 HIGH-QUALITY SOUND
Thin particular combination tone is called the dz&ence frcqwq.
When two real frequencies differ by only a few c/s, the listener
receives the impression of pulsations at the difference frequency,
which is usually called in this case the beat frequency. The process
of tuning two notes to exact unison is thus one of eliminating beats."

Biaural beats are all over the place now, but I am rather "conservative" and value the Hemi-Sync approach a bit above all other and am rather proud that my music is released by that label with added Hemi-Sync "binaural beats" layer from the "recipe" legacy of Bob Monroe.

Not really related to BBC, maybe only because Bob Monroe was also involved in radio and probably read some material like that, that triggered his interest how to replicate the altered states of mind he experienced spontaneously, via the tricking of the brain with sound.

Sorry for a little detour, but maybe it's interesting to some.

Great stuff, thanks again.

Beat frequencies and difference tones are not exactly the same as binaural beats. The former are actually there, physically in the medium and can be recorded by a microphone and seen in a waveform, also in mono, while the later are a closely related psychoacoustic phenomenon.
The first mentioning of difference tones come from Giuseppe Tartini (1692-1770) and I am sure, there were many musicians before him, that also could hear and identify them.

Thanks for pointing that out... now I am confused which they are actually describing... "the beat" frequency, the phantom pulsation they describe is the one created by the brain and is the difference between two pure tones, very close apart, isn't it?
That's what "binaural beats" and hemi-sync is based on - on the fact that brain synthesizes phantom things when both hemispheres are synchronized and it allegedly has beneficial (and interesting) psychological effects.

While the Tartini (my homie - we have his square in Piran where he was born) tones are physical and created by the ear non-linearities, when two loud notes are played simultaneously, if I am not mistaken?

Probably related, just that one goes one perceptual level deeper - from the mechanical to the mind. In the end - everything is "synthesized" in the mind anyway, just a different mechanism obviously?

Thanks for adding the distinction, but I am now not sure if the BBC is not mixing both in the description above.

Or maybe I find it hard to differentiate it all.

Beat frequencies and difference tone are basically the same thing. One is below 20Hz, the other above 20Hz. You can record something with difference tones and slow it down, so the difference tone falls under 20Hz and you will hear a pulsation. Or you just play a double stop on a bowed instrument and figure it out.
A good read is "Wie die Zeit vergeht" by Karlheinz Stockhausen. There must be translations in other languages.

These pulsations or difference tones are there in the air or in the cable or on the speaker surface as the result of waves combining. As I said, you even can see them clearly in the waveform.
Binaural beats are a little different. They don't mix in a medium. They hit the ears without any mixing in the air, cable or anything. Not even crosstalk. So the only part they could mix is inside the nervous system. So the brain kind of makes them up, which makes them a psychoacoustic phenomenon.
If the same tones would mix earlier in the medium, it would be the same, but probably less pure/impressive. And it probably would not have the same effect on brainwaves and stimulation and so on, since your brain already hears it and doesn't have to process it.

Calling difference tones "non-linearities" is also not really correct, I think. Difference tones can be problematic, if they hit nonlinearities, though. There is a big difference, playing the interval of a third into a distorting amp vs. playing it on separate guitars and amps.
A good listen for difference tones into non-linearities is Jimi Hendrix bending the a on his g string up to the b in unison with the b on the b string.