Or… bones of contention! Earmould vents (a through-hole to the outside world) can improve comfort as well as influence sound quality for better or worse.
If large, they might provoke feedback squealing, dependent on how much gain is used. If there’s no vent, or just a very small one, patient may experience a booming version of their own voice - not via the aid but through a phenomenon clinicians call ‘bone conduction’.
Having struggled for clarity in the scholarly papers, I would like to hear this term more clearly defined: does it imply that the booming voice vibration travels through the bones of the head, to be picked up by the sealed air in the ear canal then reach the drum (my layman’s guess) or is it more direct than that, as in the case of bone-conduction type hearing aids designed to directly vibrate the stapes/cochlea etc? Do we need separate terms? Is that a chorus of no thankyou I hear? Oh well!
@ellisonvoice: If you staple the cochular to the bone, will that not make it (the cochular) less free to vibrate? (I’m just a layman, too, so - I dunno …)
So many tech terms indeed SpudGunner - but hearing is fascinating, not to mention frustrating and the tech is literally in our heads, every day.
So far as I can comprehend it, one of the options for getting audio across what may be a defective outer-ear mechanism (rather than for nerve-deafness) is to apply rather strong sound in contact with the bones we can feel in the face, just behind or above the earflap, so the vibration reaches the cochlear.
In fact, some folk choose that route rather than earphones for music, and I’m told the result can be pretty good. Has the advantage of zero occlusion, too - useful to musicians. For all-day hearing assistance I think the driver unit is screwed into a pre-drilled thread!
I do hope an audiologist/academic/professor will pop up here and clarify, or flag up things we can read.
Bone conduction is defined as bone conduction. The sound does not reach the brain over the air.
This is why if you get bone conduction test you have to vibrate the mastoid bone directly. And in doing so you occlude the outer ear and give a noise to disturb the always present air vibration which disturbs the measurements.
So the vibration goes directly to the inner ear, the cochlea. The stapes is in the middle ear and is not involved in the measurement although it is with the oval window connected. There are diseases and normal variants in which the stapes contacts more or less by a hardened or scarred oval window.
Mind that hearing sounds is not just hearing tones. It is a very complex thing. Think about a tone blown by a flute or clarinet at the same loudness and frequency. Humans are able to differentiate the instrument although you have the same frequency in Herz and loudness in dB. But there are more factores then these two a human can hear.
Also your ear has a canal which is not evenly tubular. There are thicker and smaller areas and turns which influence the sound heard.
And than the whole proces in putting sound into processed sound by the brain is partially still unknown.
To make it more difficult you can imagine that you can differentiate people’s voices. Think about a musician who is choosing an instrument in a shop. The instruments could even be the same but he/ she will prefer one of them not only because of the price asked.
There is very much literature about many of the items related to human hearing. The hairs whit their length and the place they are ordned. The proces in which the contacted nerves are stimulated and the chemical and electronical processes. The locations in the brain and the cooperation with the brainstem … etc. Very interesting to know something about it. It will take you years to read all the material written on each off all these things.
But shortly said the bone conduction is the sound coming in directly by vibrating structures leading to the cochlea and bypassing the middle ear.
I am not a pro but just read some about this themes as I studied for my MD PhD. Only God knows how hearing is developed and created.
Edit:
Here is a simple article about bone conduction HA from the Hopkins clinic.