[ubuntu] exteranl microphone use on Lenovo T440p

I want to use an exteal microphone on my Lenovo T440p, which has a single "headphone" jack. I've used Audacity to record music using the inteal microphone located on upper part of the monitor. Sounds OK, but I'm sure I can do better with a decent exteal mic. I understand the headphone jack also serves as an input jack for exteal mics equipped with a 3.5mm plug. In volume control I can not determine how to disable the inteal mic. The Lenovo manual says to open control panel, click hardware and sound, then select Realtek HD manager. Guessing that's for a Windoze install. If I go to Dashboard and select "sound" and then "input" (I think this is called PulseAudio), the window will lengthen and contract as I put the microphone plug into and out of the jack, but it only shows the inteal microphone under "record sound from". That is, I don't think my exteal mic is being detected. Interestingly when I plug in headphones the "play sound from" selection changes from saying speakers to headphones.

I'd intended to buy a USB mic thinking that it would be "seen". Unfortunately I bought the wrong mic.

Also having trouble getting sound output into powered USB speakers, but that's a problem for another post...

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