• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

When you have some spare time (an hour or 2)

solderdude

Grand Contributor
Joined
Jul 21, 2018
Messages
17,687
Likes
40,656
Location
South Holland
and are interested in audio illusions psycho-acoustics/perception you should watch these excellent videos (in the order below)

1 of 7:

2 of 7:

3 of 7:

4 of 7:

5 of 7:

6 of 7:

7 of 7:
 
Last edited:
Interesting effects shown in the videos. Funny that I am not aware in daily life or audio listening what my ear/brain system does automatically.
 
Last edited:
I assume the 'illusions' will be similar/the same for all people but some of them might 'resonate' more with some people.
 
Mostly interesting!
Thanks a lot @solderdude, I'll dedicate a lot of spare time!
 
Interesting. But the interest is quickly gone as he keeps on babbling all the time, not the least on top of the demonstrations of the illusions. VERY annoying. I stopped aber the second illusion.
I do NOT hear the beating of 500Hz + 504Hz on separate ears BTW. Probably I am a freak.
 
Na ... you just cannot hear 4Hz at very low SPL.
 
and are interested in audio illusions psycho-acoustics/perception you should watch these excellent videos (in the order below)

1 of 7:

2 of 7:

3 of 7:

4 of 7:

5 of 7:

6 of 7:

7 of 7:
Thanks! The algorithm recently served me an electronic musician Maryanne Amacher (1938-2009) https://archives.nypl.org/mus/185461 who from what I can read designed music to produce artifacts in the cochlea. The Seattle AES has JJ Johnston https://www.aes.org/sections/pnw/jj.htm. on psychoacoustics.
 
@solderdude I have watched none of these yet, however, I know one thing with certainty. As I won't get to watch these until the family are asleep, I am going to be tired for work tomorrow morning. Thank you for finding and sharing.
 
Headphones are recommended for these tests. :)
 
Na ... you just cannot hear 4Hz at very low SPL.
A superposition's 'beat frequency' is not the same as a signal at the same frequency of the beat frequencies.
The frequencies are still 500 and 504 Hz, it's just that the outer envelope between constructive and destructive interference with a periodicity of 0.25 sec.
It's similar to if one pulsed a 500 Hz pure tone every 0.25 seconds. It's not a 4 Hz signal. It's a pulsed 500 Hz signal repeated 4 times a second.
Here are two visual representations of the phenomenon

1736540860799.gif

1736540815094.gif
 
Will watch the videos later.

I tried something on myself a while back.

400Hz sine wave in the left headphone, 405Hz in the right.

So both ears receive a steady tone without amplitude change.

But I hear the 5Hz difference beats (cancellation) even though they aren't there in the source.

The brain or some other part cancels the sound 5 times a second, just as if it were actually being cancelled in the air as from speakers and measurable with a microphone..

I'm not sure what I was expecting to hear, but I was a bit surprised by the result.

Intra-cranial crosstalk, I guess.

Makes me wonder how we hear stereo so clearly.
 
Will watch the videos later.

I tried something on myself a while back.

400Hz sine wave in the left headphone, 405Hz in the right.

So both ears receive a steady tone without amplitude change.

But I hear the 5Hz difference beats (cancellation) even though they aren't there in the source.

The brain or some other part cancels the sound 5 times a second, just as if it were actually being cancelled in the air as from speakers and measurable with a microphone..

I'm not sure what I was expecting to hear, but I was a bit surprised by the result.

Intra-cranial crosstalk, I guess.

Makes me wonder how we hear stereo so clearly.
Wow, tried it too! Weird stuff. I also tried with 200Hz on the left and 405Hz on the right and it did the same thing. Though when I did that I was only hearing the beat in the right ear, while the left one didn't, except that every time I nudged down or up the tone on the left I could also hear that slight tone change, while if I muted the right ear I couldn't hear that tone change.
 
Watched the first, thanks. Will following up on the others this weekend. Even I can't watch six US football games. :)
 
Anyone who's ever stood beneath a passing twin (piston) engine, prop-driven aircraft is very familiar with the heterodyne / beat effect. :)
I love that sound.

1736548648415.jpeg


Four prop engines -- even better! Very rare in the wild these days, though.
 
Will watch the videos later.

I tried something on myself a while back.

400Hz sine wave in the left headphone, 405Hz in the right.

So both ears receive a steady tone without amplitude change.

But I hear the 5Hz difference beats (cancellation) even though they aren't there in the source.

The brain or some other part cancels the sound 5 times a second, just as if it were actually being cancelled in the air as from speakers and measurable with a microphone..

I'm not sure what I was expecting to hear, but I was a bit surprised by the result.

Intra-cranial crosstalk, I guess.

Makes me wonder how we hear stereo so clearly.
Without being an audiologist, I offer the conjecture that one's brain is detecting the phase shift change between the two. Typically, if there are two different sources of the same tone one can localize 'where they are' by rotating ones head. There, it's the subtle clues from the shift in phase which assists in the localization.
 
Anyone who's ever stood beneath a passing twin (piston) engine, prop-driven aircraft is very familiar with the heterodyne / beat effect. :)
I love that sound.

I bet you wouldn't love the sound of the 8 counter rotating blades of the Soviet Tupolev Tu-95 bomber, aka Bear. :)
 
I bet you wouldn't love the sound of the 8 counter rotating blades of the Soviet Tupolev Tu-95 bomber, aka Bear. :)
I can't even imagine -- but I have read that they were are something to behold, sonically, from outside and from within. :eek:

EDIT: Of course, they're turboprops -- so not quite apples and oranges, spectrally. ;)
That said, I haven't heard the screaming whistle of a Rolls-Royce Dart turboprop for many decades -- but the sound is burned into my sonic memory! ;)
As is the grinding whine of the big Allison turboprops retrofitted to the Convair "580" twin-engined short/medium haul, medium density aircraft that were, thanks to Allegheny Airlines, fairly common in my younger days.


source:

Not my photo, but I saw many CV-580s from the very same spot on the observation deck at Baltimore's old "Friendship Airport" (now Thurgood Marshall/Baltimore-Washington International) terminal about 4 miles from my childhood house. :)

I'll stop now, I promise. :facepalm:
 

Attachments

  • 1736556783363.png
    1736556783363.png
    571.4 KB · Views: 16
Last edited:
Back
Top Bottom