psychoacoustics

[steevio]

we are talking about harmonics, you are talking about interference between waves.

with harmonics there is no interference, they are all mathematically related (mulitples)

infact its the exact opposite of interference.

[hairblz]

for instance when you play two notes together which are harmonically related, you dont just hear two notes, you also hear a lower note which is the difference between the two notes.

This is caused by interference, and happens with all notes, not just harmonically related ones.

If you agree with me that this is true, then I will admit that I am absolutely confused about this topic. If you disagree then I will read up some more, you don't have to explain it to me.

[steevio]

we are talking about a psychoacoustic effect, the wave isnt really there, you are talking about 'beating' caused by amplitude intereference of the waves, that really is there in the physical world, it not created by your brain.
with harmonics, there is no beating,
you are talking about a physical effect, you say happens inside the ear drum. thats not psychoacoustic is it ?

from what i remember the perceived frequency of two waves of different frequency is the average of the two, f = 1/2(f1+f2)

[AK]

I know about this too, well- at least a little bit. it's interesting to a point. But I can't think about that sort of depth. I don't even get time to even turn the little studio on, never mind start thinking about this. I do educate myself though and I'd like to think I'm experienced in what I know but this sh!t is deep.

[hairblz]

if we could really just hear the two frequencies without the psychoacoustic effects, what would they really sound like ?

Have you tried panning the two frequencies left and right, while listening with headphones?

[optX]

hairblz : I think Steevio is right, it`s quite the opposite.

Intermodulation is a known, fully explored and explainable topic and mainly used by electrotechnicians whereas missing fundamentals and fund./overtone listening is an unexplainable topic in the psychoacoustics.

The difference between them can be nicely explained when you look at 2 or 3-way speakers and their crossover (frequency).
The speaker design with separate housings for each speaker is developed (among other things) because you can avoid intermodulation/interference between them which can lead to signal-degredation/erasement/phaseshift or generation of unwanted/unpleasend noise and on the other hand because you can route back the low/mid signal via the crossover to achieve harmonics in the low/lowmid range to accomplish those missing fundamentals with this you can design a speaker which sounds bass-heavier than it actually is.

I don`t know if my explanation here is 100% right but a lot of speaker developers are doing this to make their products sound bassheavy. Here you can see why a 5" bassheavy sounding KRK isn`t the same quality (bass-wise) as a 8" or even fullrange monitor.

[steevio]

if we could really just hear the two frequencies without the psychoacoustic effects, what would they really sound like ?

Have you tried panning the two frequencies left and right, while listening with headphones?

yeah mate, i have done experiments with this before, what you are talking about is 'binaural beats'

i built a 'brain machine' a few years ago which works in a similar way with alternately flashing LEDs in each eye and binaural beats in headphones, it really trips you out. they are sold as meditation devices for a few hundred pounds, but you can make one with just a few components for next to nothing.

its another psychoacoustic effect, but its not the 'missing fundamental' effect.

you have two slightly different frequencies one in each ear, and although the two frequencies are totally seperate and do not actually interfere in the real world, they still beat in your head, which actually contradicts what you are saying about it dissappearing when you do that, ( maybe you are one of the people who hears in overtones ? )

http://en.wikipedia.org/wiki/Binaural_beats

the missing fundamental effect does not require that the two frequencies go to seperate ears, its a particular property of harmonically related sound waves and how the brain perceives them.

we are talking about two very similar and related topics, but i think you've got them mixed up a bit thats all i'm saying.

i was going to say 'we are on slightly different wavelengths' but then thought better of it.

[hairblz]

I do know the difference between beating and missing fundamentals.

Subjective tones (sidebands; difference tones, sum tones, missing fundamentals) are ALL examples of interference and distortion caused by the non-linear behaviour of the ear.

maybe you are one of the people who hears in overtones ? )

Perhaps!

When I did the experiment, the beating definitely went away, it was a heavy 1Hz pulse in amplitude, which was visible in the meters, then it went away.

I also tried creating missing fundamentals. I did this by having three tones playing - 300, 400, and 500Hz. In theory, I should hear a missing fundamental of 100Hz, but I didn't hear anything. I also tried 1200, 1400 and 1600Hz, no 200Hz tone to be heard though.