Column listening device?

[bunny]

The column that I use for potable product does not have a sight glass.
My test column does have a Seiko watch crystal siliconed onto a tee, but it's a test column made from readily available materials.

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I would like to listen to the sounds of my column running at it's most efficient/productive speed.
Ideally I would like to plug the device into the aux jack on a Sangean portable radio.
This would give me "background" sound while working in my one car garage with a car in it and stop scorching my ears on hot copper.


I haven't found something suitable as of yet and am not an electronics wizard.
Was wondering if anyone has something like this and would share with us(me) less creative types?