In-ear-canal microphones...

Thread Starter

Externet

Joined Nov 29, 2005
1,932
Hello.
Microphones used in-ear-canal being also earphones; do they share the magnetic transducer for both actions or there is separate electret as microphone plus a magnetic as earphone ?
 

kubeek

Joined Sep 20, 2005
5,776
Imagine noise cancelling headphones, the microphone has to be separate from the speaker, otherwise you cannot do the playing and correcting at the same time. (not sure if the microphone is placed in the ear canal, outside or both).

Other than that, do you have some link to earphones that you describe? Is it for binaural recording and playback or?
 

Thread Starter

Externet

Joined Nov 29, 2005
1,932
Thanks. Just imagining an earbud for simplex intercoms doubling as microphone. Motorola has some 'special applications' units. Faintly remember if amateur radio had those.
 

kubeek

Joined Sep 20, 2005
5,776
For that, have you tried in-ear earbuds? The isolation that they provide from the outside world is pretty good. Not sure how the human voice sounds like inside a blocked ear canal as it is transmitted up there from the mouth through bones and tissue, but I doubt it would be very nice to hear and transmit over radio. I would imagine very bassy sound and very little sibilants, so speech would not be very intelligible.
 

Thread Starter

Externet

Joined Nov 29, 2005
1,932
Have not tried an in-ear-canal-microphone with included earphone functionality. Trying to learn how are they made. I too suspect poor intelligibility in need of serious DSP processing.
Bone conduction, throat mics are yet other animals which should also yield poor intelligibility. But they are used for their own niches.


 
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jbeng

Joined Sep 10, 2006
84
I have a pair of hands-free communicators from Maxon which have an earphone mic. They are quite old, so I don't believe they would have both mic and earphone elements in the same housing. The model is 49-FX, so if you could get your hands on the schematic, it would probably be of great use to you.
Here's a pic of the product box for your reference.
Maxon 49-fx box.jpg
 

Thread Starter

Externet

Joined Nov 29, 2005
1,932
Thanks, jbeng. Very good clue.
Looking at the 49-fx, seems the earpiece has a fixed connection to the intercom, with no way to tell how many conductors to guess if uses electret+dynamic in there.
Will dig deeper... :)
Edited... Found this, which does not make sense with input and output separate jacks :

Screenshot from 2019-09-16 10-17-40.png
 
Last edited:

Audioguru

Joined Dec 20, 2007
11,248
Stick the microphone in front of your mouth where it belongs.
TV announcers and movie actors always try to hide their microphones which makes their speech unintelligible.
 

MisterBill2

Joined Jan 23, 2018
13,128
I recently came across an article about that in a rather old publication. There is only one transducer, and the application mentioned was SIMPLEX, not duplex like a telephone call. Push to talk, release to listen. For that type of operation it can work. For duplex the very best it can provide is quite poor, and not worth the effort.
 

jbeng

Joined Sep 10, 2006
84
@Externet - I don't think the diagram you show is the one for those radios. I saw that same diagram and it looks like a guitar effect unit to me, since there is (was?) a company called "Maxon" with a product line of guitar effect pedals. I haven't yet been able to locate a schematic for a Maxon 49-FX radio.
 

MisterBill2

Joined Jan 23, 2018
13,128
@Externet - I don't think the diagram you show is the one for those radios. I saw that same diagram and it looks like a guitar effect unit to me, since there is (was?) a company called "Maxon" with a product line of guitar effect pedals. I haven't yet been able to locate a schematic for a Maxon 49-FX radio.
Maxon does produce a line of mobile radios, at least some company with that name did a while back. But not everything posted on the internet is true, and while some of it is just errors, other parts are total lies.
The same earpiece could serve as either an earphone or an ear-mic, but not in a duplex mode, I don't think. I may try and see just what I can make work some time soon. The one thing that I see as a problem is that the leads are not shielded. Since I also may try a crystal earphone that I have, which is very high impedance, the lack of shielding may be a problem, because I would be using an AC mains powered amplifier.
 
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