[oluv]

can someone explain to me acoustically why the bass disappears as soon as you lose the seal with your tips. what is the physical explanation for this? is this some kind of acoustic short-circuit? that means that the backside out-of-phase sonic waves kill the in-phase waves that go inside the ear-canal? or is this some other effect?

i would really appreciate any explanation.

 

[karma]

Well, I'm no expert, but I'll take a stab at it.

Bass is non-directional and primarily felt more than heard. Having a good seal allows the bass to "rumble" or bounce around in your ear, giving you a stronger sensation of its presence. Same as how the recommended placement of a subwoofer is in a corner so that the walls can effectively reverb and enhance the punch. Losing the seal allows the bass to escape, thereby reducing its overall impact.

 

[Necros]

And taking a speaker sub driver out of the cabinet is another example..it looses all bass response.

 

[MD1032]

Without a good seal, the air pressure inside cannot stay constant and the higher SPL's created by the bass will simply leak right out.

 

[Cyclone]

vibrations travel best through solid objects(through your ear canal to your ear drum), not so great through air, and much worse through water. coincidentally this is why when you have good seal with your canal buds and you tap the cord it sounds quite loud.

 

[hawkfire]

hello,

The answer is called resonance.

 

[Jmmmmm]

i dont want to say most of these answers are wrong...but i don't know if theyre right.
I don't know how resonance is affected by lack of (or presence of) a seal.
My guess is that since bass a very slow moving wave, when you don't have a seal, the background noise leaks in and the organized wave from the tiny driver is either disturbed by this moving air, or your ear isn't able to distinguish it from the background noise, so you don't hear it. That's my educated guess, though probably not right either.

 

[Zuerst]

I don't think this is scientific or anything but try blowing air on your palm. Then cover your mouth with your palm and try to blow again.

 

[hawkfire]

hello,

guessing doesnt work.

The answer is still resonance if you want the scientific answer.

In the case of the etys, it is a matter of resonance + vacuum + armature driver and has nothing to do with outside noise whatsoever.

 

[mrkangpae]

Quote:

Originally Posted by hawkfire hello, guessing doesnt work. The answer is still resonance if you want the scientific answer. In the case of the etys, it is a matter of resonance + vacuum + armature driver and has nothing to do with outside noise whatsoever.

Please be more descriptive. One word answers don't really allow us to do much more than guess.

 

[JaZZ]

The tiny membrane has a quite high resonance frequency without any load. Add to this that the tiny membrane can't move much air, which is needed for bass. Longer sound waves have much higher amplitudes than high frequencies. So the driver principle relies on an airtight seal to 1) create a higher moving mass by forming an entity between membrane, enclosed air and eardrum for lower resonance frequency and 2) avoid loss of sound pressure with low frequencies.

 

[JohnRich]

lol, I like the zuerst line of reasoning best so far.

The low (bass) frequencies require more energy for transmission through air than high ones; if you don't seal the ear then the driver is having to expend that energy to vibrate a larger mass of air, and hence less volume will reach the ear drum.

and sorry to disagree, but guessing does work; it just doesn't work all of the time.

Not sure how *resonance* could account for the presence or absence of bass; the air resonates in response to the transducer with or without a seal; the difference is in over what volume of air and hence at what amplitude.

 

[hawkfire]

hello,

Jazz,

you speak in reference to dynamic aka diaphram (membrane) design drivers.

Only canalphones that use these that I know of are the Sennheiser IEM3 aka futuresonics EM3.

And technically there is no air to push around in a vacuum making your theory inaccurate as well.

Thats why armature driver design is used for full sealed canalphones AKA IEMS.

An armature driver is basically just a small rectangular metal (In most cases aluminum) box with an enclosed magnetically balanced shaft or armature.

think in terms of a circumarual headphone.

Circumarual headphones are normally a membrane type driver cased in a cup which goes over your ears creating a sealed chamber for resonance.

Thats the basic theory canalphones try to emulate using your ear canals not only to tune each armature driver, but also to create a resonance chamber for bass response as well.

no seal=NO resonance=no bass response or balanced sound.

Also, its one of the reasons why people have so many varying opinions about EIMS in general since nobody has identicle ear canal shapes or lengths.

In fact no two ear canal shape or lengths are the same. even on the same person.

Thats basically it in a nutshell.

 

[mrkangpae]

Quote:

Originally Posted by JohnRich lol, I like the zuerst line of reasoning best so far. The low (bass) frequencies require more energy for transmission through air than high ones; if you don't seal the ear then the driver is having to expend that energy to vibrate a larger mass of air, and hence less volume will reach the ear drum. and sorry to disagree, but guessing does work; it just doesn't work all of the time. Not sure how *resonance* could account for the presence or absence of bass; the air resonates in response to the transducer with or without a seal; the difference is in over what volume of air and hence at what amplitude.

JohnRich's line of reasoning makes the most sense to me.

 

[Jmmmmm]

sorry to be difficult hawkeye, but two things:
1. where is there a vacuum in this equation? i dont understand why you mention this, unless jazz's explanation relies on being in a vacuum, which it doesn't seem to, to me.
2. i dont think you have explained how resonance is involved at all. does the sealed canal provide a chamber for the waves to add, or prevent destruction of waves, or what. I think you need to give a more thorough explanation.

also, only some canalphones are armatures, but all canalphones require a seal for appropriate bass, as far as i know.