Binaural beats

[vk6zgo]

Tones:
If you sum two sine waves, you will see two "tones" or "lines" in the frequency domain, when using a spectrum analyzer.
What you see on an oscilloscope is in the time domain.
If your oscilloscope supports a Fourier transform, you can analyze the time-domain data to get the frequency domain, and should see two lines in that domain.

Since my "oscilloscope" lacks a Fourier transform and is not a spectrum analyzer, I cannot see two distinct tones. So that earlier statement was wrong.

If you input the two tones to one channel of an analog oscilloscope, you will see a constantly changing display, as over time,  the two tones reinforce or cancel depending upon the instantaneous levels & timing of those signals.

I have never done such a test with a DSO, but am fairly sure that a fully featured one would give the same result, unless you specifically required it to give a display like your "virtual" 'scope.

[TimFox]

The graphs I showed in my post above were done by simply generating two columns in an Excel spreadsheet for each of the two frequencies (1000 and 1100 Hz), vs. time in the first column.
From that, I computed the sum signal and the magnitude in two more columns.
The graphs were generated directly from those columns and represent what an oscilloscope would show for a single sweep (that happened to start when both sinusoids started from zero).

[BrianHG]

See my post here:

https://www.eevblog.com/forum/chat/fun-for-nerds/msg5982747/#msg5982747

There is a section describing what happens when you mix 2 sine waves.

[tggzzz]

See my post here:

https://www.eevblog.com/forum/chat/fun-for-nerds/msg5982747/#msg5982747

There is a section describing what happens when you mix 2 sine waves.

That's "mix" as in "add", i.e. the audio engineer's operation.
Not "mix" as in "multiply", i.e. the radio engineer's operation.

[fourfathom]

Tones:
If you sum two sine waves, you will see two "tones" or "lines" in the frequency domain, when using a spectrum analyzer.
What you see on an oscilloscope is in the time domain.
If your oscilloscope supports a Fourier transform, you can analyze the time-domain data to get the frequency domain, and should see two lines in that domain.

Since my "oscilloscope" lacks a Fourier transform and is not a spectrum analyzer, I cannot see two distinct tones. So that earlier statement was wrong.

If you input the two tones to one channel of an analog oscilloscope, you will see a constantly changing display, as over time,  the two tones reinforce or cancel depending upon the instantaneous levels & timing of those signals.

I have never done such a test with a DSO, but am fairly sure that a fully featured one would give the same result, unless you specifically required it to give a display like your "virtual" 'scope.

A digital scope will give the same display as long as you set up the triggering and sample rate appropriately.  Same for triggering with an analog scope.  Analog Kid's virtual scope is also correctly displaying an additive audio beat, just the same as you would see with a single-sweep on any other scope.

And as Tgqzzz noted, "mixing" has different meanings in different domains.  A sound-tech's mixer panel is an additive mixer.

[BrianHG]

Anyone try out the free 3 day trial of:

https://www.brain.fm/

They say they do not use binaural beats, yet listening to their 'study' / 'focus', they are applying what appears to be a global volume modulation effect with added background noise.  I'm not sure how they got so many positive reviews, with BS FMRI scans which only show a brain being globally over activated/stressed instead of proper focus in key regions dedicated to deep concentration.  All I get is a headache from using it.

Maybe if they focused on the quality of the artificial music instead of the BS effects, I might have considered it useful.

I stick with real music.

[paulca]

How does this relate to the time domain, as in the delay component and reflections between ears and lobes.

There has been some success in producing 3D spacial "feeling" from just 2 speakers.  So this is tapping the brains millisecond delay perception and pattern matching of ear lobe reflections etc.   Used to position sounds in 3D space in the world model.

If you combine the two close frequencies in two ears could trigger a spacial sensation of the sound moving around.

I believe it matters greatly what the waveform is too.  IIRC a sine wave is very difficult for the ear to locate, forcing nearly everyone to "cock their head like a dog" when you play one.  The impulse is to rotate your head to probably non-random angles to try and interrupt the phase and get a bearing on the signal.

[RJSV]

   One contribution to the discussion:
   When a single ear hears a sound,  there is a crude sort of directionality due to the frequency response of the ear shape.   I guess the brain has a highly complex response, that figures out direction.
   Example:   A noise up and behind the head maybe has a certain brain response,  with 'muffled' quality on the very high frequencies, or harmonics.   Same noise more towards the front, or face, forehead etc. might be less muffled.
   So a cat or whatever,  can track the nearby mouse,  via this effect.  But I'm not able to muse about how a brain gets the 'original template' or learns the original noise and expected harmonics.  (Maybe researcher's don't yet know ?).

   But, for sure,  that cat 'knows' roughly where the mouse is, using only one ear, and the response variations versus angle of reception.
Plugging THAT in,  I wonder how things work when a cat, or human has normal TWO ears working the mouse sounds,  each with a decision about 'where',  at what angle,  into each ear.
   If each ear can find out the angle of arrival,  then triangulation could give a crude estimate of both direction and distance for predator and prey interactions.

  Most CATS seem wired for Compulsive response,  by focus focus focus,  (when a higher frequency mouse sound is present nearby)!

[RJSV]

   One idea just now,  is that, with a single ear,  a MOVING source provides a sound that has a variation in perception.  If the sound's high frequencies increase,  then the brain can assume a source of that is currently moving towards the front of the head.
   That way,  the animal doesn't need a big library of response types,  just a relative sense,  of frequency responses,  now, and 100 msec. ago.

(No matter how nominal the animal). (Hello, my friend)

[RJSV]

   To member Temperance:
   I hesitated to bring up some hassles that cooled down,  regarding aNALOG kID.  But,  he had been civil, but after s similar spate of uncool encounters (quick to issue the "Fuck You" to a non-familiar member).
(I think I did read ONE Original Posted thread,  since 2025 started.)
   I was annoyed,  and then it got worse;   He (a.k.) very consistently came back in (my) face, like 17 minutes after my post,  and fired off some really just cheap, jerky,  'snark' I termed it:  (approximate quotes):

   "Rick,  that used record player you claim to be enjoying...is total garbage consumer product!".    Ah-ha;  now I know...uh...something ?

   "WE don't like reading your messed up Word Salad posts"
Ah-ha!  (Our self-appointed LEADER).   Other members have expressed dismay,  over the clarity of my posts,  and it looks like he just picked up, on that.  No value really.

   Thing is:  he generally seemed to come back, hard, with some cheap, useless REPLY,  and within less than 29 minutes after my own post.
So it got to be an auto-learned near-phobia:
   "Ahhhh shittttt;  There he is...only 17 minutes after my post, with a really stupid non-contribution!"

   Confronted,  he issued the 'Fuck You then' reply...again after 12.5 minutes.   I responded that:
   "Can you please,PLEASE wait an hour or something,  before I get the thumbs down, from our newly self-appointed leader-boy ? !"

   But nope:  even that got the snarky return, fuck you content-free utterance.   He seems smart,  like an A.I.Bot,  he seems fast, like an A.I. bot might.  Certainly no respect for Dave,  and the real rules, for posts, like an AI. BOT.

   Recently,  another member asked him to stop with the negativity, if he had nothing to contribute. (I felt my position get vindicated, by another reaction).   But,  he got better, on my topics at least, (so I laid off the defensive watching out, for his crap).

   Now,  I read this, recent waste and chain-pulling of random member's topic discussion.  Motivation psychology mentions:
   'Sadistic blah blah blah - narcissistic etc.'. was the jargon used,  which I couldn't decipher, totally, (the motivation of disrupters).

Smart, smarmy quick Disrupter.   Has its basis,  for the worthless antagonism...(in a bar maybe).

Rick B.