earbuds...

[legionserial]

A while back someone posted a link to a website that actually demonstrated this illusion using WAV or MP3 tones generated by clicking different notes on a scale. I didn't keep that URL, but maybe a reader has it and can post it here?.

I'm not sure if the link below is what you are talking about, but if not it has similar fundamentals at least...I think.

The idea being that you play the notes around this circular keyboard, and they appear to be constantly ascending or descending depending on what direction you go round the keyboard. The reason being that each note is actually playing 6 octaves of the same note at the same time. tricking the brain into thinking it is contantly descending or ascending.

I do have an mp3 that could be looped to the same effect, which demonstrates it a lot better I think (as the response of the keys in below link is a bit glitchy at times), but don't have anywhere to host it right now, and I can't remember where the hell I got it from.

http://www.exploratorium.edu/exhibits/highest_note/fr.discrete.html

 

[Tim Gillett]

Simple acoustics and the relationships of the overtones to the fundamental.

The first overtone is defined to be an octave higher from the fundamental.
The second overtone is an octave+5th above the fundamental.
The 3rd overtone is 2 octaves above the fundamental.

Just with these 3 overtones you can already infer what the fundamental frequency is (or should be).

Given your example, if you have a 100hz tone and it is the first overtone, then the second overtone is going to be 150hz, with the fundamental (real or inferred) at 50hz. However, had your 100hz tone actually been the fundamental, you wouldn't have a 150hz overtone. The first overtone in this case would be 200hz. So, given your example, just the presence of a 150hz tone above the 100hz tone would suggest that there is a 50hz fundamental.

Hope that makes sense

BTW just an interesting tidbit, most modern brass instruments (aside from the tuba) have a very hard time reproducing the fundamental which should be theoretically possible given the length of their tubing due to the fact that they are rather narrow. Their "real" range normally starts from the first "overtone". Going further back, the old baroque and classical era valvless trumpets and horns couldn't even reproduce that, instead starting on the 3rd overtone, which kinda helped them in being able to play more melodic passages by pushing the playable "harmonic series" further up, where they're lined up closer to one another.

Did I just muddy the waters some more?

No not at all. Makes perfect sense. Hearing that series of overtones is just like hearing the full deal but minus the fundamental. Interesting you use the word "infer" what the fundamental is or should be. Closer to what I was trying to say about "working it out" rather than our hearing a kind of phantom of it. An important distinction?

But I'd still like to HEAR the effect for myself. Short of getting the website examples maybe I'll just play a bass guitar line into the recorder, shave off the fundamental and see if I can still "hear" that fundamental.
The theory is fine as far as it goes but I'm the type that has to confirm it for myself, especially by hearing it. That's real learning, not second hand knowledge.

Interesting comments about the brass instruments. As a muso I'm primarily a guitar and bass player and am very sensitive to having two bass type instruments (similar bass fundamentals) like an electric bass and a keyboard playing the same low bass notes. In live gigs I generally make an agreement with the other muso that one of us, it doesnt matter who, will sacrifice our bass fundamental tones (with a bit of high pass filtering) so there's only one set of low bass tones going out through the same FOH speakers. Otherwise a recipe for beats problems and general muddiness.

Thanks for your comments.

Tim

 

[Tim Gillett]

Not to mention that the beat frequency of 150Hz and 100Hz is.....









Come on.........





















You guessed it!!!!!











Yup! it's 50Hz!

Wow, what a mathematician!

But what's your inference? That the illusion we hear IS this beat? If so, say so, and for all I know you may be right.

But is the sarcasm really necessary?

Regards, Tim

 

[legionserial]

I get whats being said about harmonic overtones, but where does this fit in with more percussive sounds? Is that the same principle?

 

[SouthSIDE Glen]

I have not yet found the exact website that was given before, but here is a gaggle of websites discussing and describing the "Missing Fundamental" or "Virtual Pitch" effect. Some of these pages include audio clip examples of the effect in action.

http://www.answers.com/topic/missing-fundamental
http://physics.mtsu.edu/~wmr/julianna.html
http://hyperphysics.phy-astr.gsu.edu/hbase/sound/subton.html#c2
http://www.ee.calpoly.edu/~jbreiten/audio/missfund/
http://homepage.ntu.edu.tw/~karchung/Phonetics II page thirteen.htm
http://www.acoustics.org/press/138th/lewis.htm

It appears there is not complete agreement on exactly *why* the effect works. Some explain it in terms of the BFOs as Jay pointed out, but it seems the closer you actually get to audiologists and the acoustical scientists who are supposed to be the experts at this stuff, the less sure they are of the fundamental (cheap pun intended) reason behind the effect.

And for Tim: here's another phrase to add to the "synthesize" vs. "working it out" semantic. As described in that last link in the list above: "the brain may fill in missing parts". But it should be fairly clear after reading the above links that the effect is indeed one where the brain is "hearing" a fundamental that is not actually present.

G.

 

[Farview]

Wow, what a mathematician!

(sniff,sniff) Do you smell that? That's sarcasm!

But what's your inference? That the illusion we hear IS this beat? If so, say so, and for all I know you may be right.

Yup.

But is the sarcasm really necessary?

Just a reaction to what I interpreted as the combative nature of your posts.


Guitar and bass are going to be hard to test the theory with. Both of those instruments have a second harmonic that is (much) stronger than the fundamental. A lot of stringed instruments are that way.

 

[Robert D]

I'm going to stay out of the psychoacoustics here, and just comment on the coupling factor. Earbuds work at low frequencies, as mentioned above, because they don't have to move much air, yes. More than that though, you'll notice that the bass response changes radically as you just un-seat them from your ear, even though the distance to your eardrum has hardly changed. This, I'm guessing, is the same effect as a regular speaker operating in an enclosure, vs free standing. In other words, your ear becomes the speaker enclosure for the driver in the earbud.

 

[SouthSIDE Glen]

In other words, your ear becomes the speaker enclosure for the driver in the earbud.

I think that may be a pretty good point, Rob. This stingy BBS ( ) won't let me rep you for that observation; I owe you one.

Bringing the topic back to the "missing fundamental" effect for just a second (and for those who missed it because the post got buried at the bottom of page 1, there's a list in post #24 of a lot of web pages going into the effect in some detail, along with several audio examples), I do have my own follow up questions about that...

There are a few references (including links I did not include in that list) that refer to how the effect is utilized in modern systems with small speakers (such as earbuds) to overcome the physical shortcoming in the bass response of those systems - as was the original point in this discussion of the effect. The questions I have about that, though, is whether there is intentional *design* meant to accentuate that effect?

In other words, is there either A) intentional active circuitry in systems like a mePod that analyzes the low bass fundamentals in the signal and then boosts their overtones in a sort of reverse harmonic filter in order to boost the effect? or B) design in the buds and small speakers themselves where they physically respond to the bass signals by pushing at the overtones?

Or are they simply counting on nature to take it's course and letting the "missing fundamental" effect do it's thing naturally (combined with the added effects of physical coupling and small ear canal volume and so forth?)

G.

 

[boingoman]

Both of those instruments have a first harmonic that is (much) stronger than the fundamental. A lot of stringed instruments are that way.

Fundamental= first harmonic. Same thing.

Second harmonic= first overtone

All the harmonics get plastered together by our brain/ears.

One theory of the missing fundamental has to do with the math of the overtones.

If you have 100hz, and 200, 300, 400, 500hz overtones, if you take out the 100hz tone, your brain may interpolate the fundamental from the overtones, since there is only one frequency, 100hz, that makes the series work out.

 

[Farview]

Fundamental= first harmonic. Same thing.

Second harmonic= first overtone

All the harmonics get plastered together by our brain/ears.

One theory of the missing fundamental has to do with the math of the overtones.

If you have 100hz, and 200, 300, 400, 500hz overtones, if you take out the 100hz tone, your brain may interpolate the fundamental from the overtones, since there is only one frequency, 100hz, that makes the series work out.

Typo fixed.

 

[rayc]

Tim,
MP3 compression & LOSS is a million miles away from RIAA EQ. & the bass boost I speak of, those tacky buttons or switches on cheap CD players & most MP3 players creates sounds that could only be enjoyed by those who've not experienced near natural bass.
1. MEGA bass et al aren't real, it's not compensation or even over compensation - it's a way of covering up bad processing or bad reproduction or BOTH.
It's the sort of stuff you need in a car to humble the sound of the motor.
Oh, & yes Bose does have a bass boost but it is, usually, mathematically calculated to represent response that is otherwise lost - in other words a fair guestimate of compensation. I have a pair of Bose living room floorstanding direct/reflection speakers that have bass boost/compensation through a port and the size/shape of the structure. Oh, I also have a bass control on my almost every stereo amp in the house but I don't crank it to max regardless of what I'm playing - partly because my vinyl is played through a good t/table & amp with reliable RIAA EQ, my tapes are fairly well recorded & the Cds, well depending on whether they've been remastered for the format or not I may tweak the EQ, beyond the fairly static room compensating settings, as needed.
My MP3 player - I use it rarely, I use decent headphones & I accept that the sound & EQ settings are compromised so I set it up to be non mega & acknowledge it's shortcoming while I walk to the corer shop- I certainly don't mix to the format.
2. MP3s don't inherently lack bass they inherently lack a whole lot more musical information than they contain.
3. Perhaps your bone needs more density. You're right but I'm not wrong.
I'd venture the opin that you're rather like a dog at a bone on this topic & have lost perspective re the steak on the plate beside you.

 

[Tim Gillett]

Tim,
MP3 compression & LOSS is a million miles away from RIAA EQ. & the bass boost I speak of, those tacky buttons or switches on cheap CD players & most MP3 players creates sounds that could only be enjoyed by those who've not experienced near natural bass.
1. MEGA bass et al aren't real, it's not compensation or even over compensation - it's a way of covering up bad processing or bad reproduction or BOTH.
It's the sort of stuff you need in a car to humble the sound of the motor.
Oh, & yes Bose does have a bass boost but it is, usually, mathematically calculated to represent response that is otherwise lost - in other words a fair guestimate of compensation. I have a pair of Bose living room floorstanding direct/reflection speakers that have bass boost/compensation through a port and the size/shape of the structure. Oh, I also have a bass control on my almost every stereo amp in the house but I don't crank it to max regardless of what I'm playing - partly because my vinyl is played through a good t/table & amp with reliable RIAA EQ, my tapes are fairly well recorded & the Cds, well depending on whether they've been remastered for the format or not I may tweak the EQ, beyond the fairly static room compensating settings, as needed.
My MP3 player - I use it rarely, I use decent headphones & I accept that the sound & EQ settings are compromised so I set it up to be non mega & acknowledge it's shortcoming while I walk to the corer shop- I certainly don't mix to the format.
2. MP3s don't inherently lack bass they inherently lack a whole lot more musical information than they contain.
3. Perhaps your bone needs more density. You're right but I'm not wrong.
I'd venture the opin that you're rather like a dog at a bone on this topic & have lost perspective re the steak on the plate beside you.

rayc,
I wasnt even talking about mp3 there. I was talking about bass boost to compensate for bass lack in headphones.

Insofar as I did mention mp3 it was to say that mp3's dont have an inherent lack of bass. You agreed with me but then said mp3's "lack a whole lot more musical information than they contain." That's a broad generalisation which applies in some instances and not others. mp3's arent all the same. It is a compression standard in which the amount of compression can be varied by the user to suit the use.

Sure, the bass boost or mega bass on many cheap players is probably poorly matched, if at all, to the headphones sold with them but is that a surprise? You get what you pay for.

In any case, I said nothing about how good the bass boost fits the headphones. You have no argument with me because I didnt say anything on this. I was talking about headphones and their lack of bass, not mp3 files. Bass boost on portable players really has nothing to do with the fact the files played are mp3, regardless of how good or bad it otherwise is.

BTW certain Bose speakers, both consumer and commercial used active eq, with bass and treble boost.

You seem to imply I suggested people should crank their home stereo bass control to max regardless of whether the effect is good or bad. Would you please highlight exactly where I said that because I cant find it so far...

You dont mix to mp3? Neither do many others including myself. But how does that relate to what we were talking about?

You suggest I'm like a dog at a bone on this topic. Then why did I not continue to post on this thread thinking, perhaps like most others, it was dead days ago, but you are now restarting it? You have a perfect right to continue the thread, as I have also. But as to me being like a dog at a bone... please get your facts straight.

You restarted the thread, not me. And now you have a reply.



Tim.

 

[rayc]

...but Tim, I wasn't arguing with you I was giving my perspective. It was you who took exception not I!
...but Tim you mentioned MP3 twice in your 1st response to me!!!
...but Tim you did keep coming back & gnawing away at other people's comments when they didn't align with your own!
...but Tim I reponded when I came across the thread again - sorry if my timeframe doesn't match/correspond/fit comfortabley with yours!
...but Tim...no I can't keep going on I'm getting images of South Park in my head.