Speaker into a tube - what happens

[David James]

I went for a hearing test and the audiology clinic used a kind of “in ear monitor” with, from what I could tell, transducers coupled to a tube, similar to silicon tubing, and then to foam plugs on the other end. I’ve attached an image of something that looks like it could be the same. I always thought a long tube was a bad thing but the sound of the technician’s voice was uncannily clear.

This has made me curious about what happens when a transducer is coupled directly to a tube like this. My experience at the clinic suggests that the transmission is linear but I don’t know any of the science. The complexity of transmission line enclosures made me assume things for very complicated in such a situation.

 

[Blumlein 88]

I've not seen anything like that. However, I notice the name Etymotic on them. So those guys make some very good IEMs. I have a pair and they are darned clear, but I hate how deep they have to go. They did originally do business for what I suppose would be called audiometric gear.

 

[fpitas]

A tube is only bad if it's not properly terminated at one end to eliminate pipe resonances.

 

[FrankW]

It should sound more musical with less glare

 

[David James]

It should sound more musical with less glare

If you have nothing to say about the science here then please stay out of my thread.

 

[dasdoing]

probably for isolation

 

[David James]

A tube is only bad if it's not properly terminated at one end to eliminate pipe resonances.

In this case they terminate in my ear canal.

Could you elaborate on what “properly terminated” means?

 

[FrankW]

My guess is no mag field
https://shop.neurospec.com/er30-tub...00-ohm?___store=en_US&___from_store=x_default

 

[NTK]

Why Your Clinic Should Switch to Insert Earphones - The EI Group

In a previous blog, a brief history was provided concerning the 30-year effort by hearing conservation professionals to obtain approval from OSHA in 2013 for the use of insert earphones rather than supra-aural headphones. For audiometric testing, Audiologists have used insert earphones in...

ei1.com

 

[David James]

i think I was unclear about what I want to know.

What happens to the sound if the transducer is coupled tightly to a long tube, as it is in device in the picture?

 

[fpitas]

In this case they terminate in my ear canal.

Could you elaborate on what “properly terminated” means?

In this case it must be terminated at the sending end in its characteristic acoustic impedance.

 

[David James]

My guess is no mag field
https://shop.neurospec.com/er30-tub...00-ohm?___store=en_US&___from_store=x_default

Yes, I read that too and it seems to be what these are made for, but the set in the audiology clinic I described use the same technology (they might have been the same model) and one would assume in that setting that there are certain requirements for accuracy. This has made me curious about something I clearly misunderstood.