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Message ID: 16955     Entry time: Tue Jun 28 16:26:58 2022
Author: Cici 
Type: Summary 
Category: General 
Subject: Vector fitting open loop transfer function/Audio cancellation of optical table enclosure 

[Deeksha, Cici]

We attempted to use vectfit to fit our earlier transfer function data, and were generally unsuccessful (see vectfit_firstattempt.png), but are much closer to understanding vectfit than before. Couple of problems to address - finding the right set of initial poles to start with has been very hard, and also however vectfit is plotting the phase data is unwrapping it, which makes it generally unreadable. Still working on how to mess with the vectfit automatically-generated plots. In general, our data is very messy (this is old data of the transfer function from last week), so we took more data today to see if our coherence was the problem (see TFSR785_28-06-2022_161937.pdf). As is visible from the graph, our coherence is terrible, and above 1kHz is almost entirely below 0.5 (or 0.2) on both channels. Figuring out why this is and fixing it is our first priority.

In the process of taking new data, we also found out that the optical table enclosure at the end of the X-arm does a decent job of sound isolation (see enclosure_open.mp4 and enclosure_closed.mp4). The clicking from the shutter is visible on a spectrogram at high frequencies when the enclosure is open, but not when it is closed. We also discovered that the script to toggle the shutter can run indefinitely, which can break the shutter, so we need to fix that problem!

Attachment 1: vectfit_firstattempt.png  61 kB  Uploaded Tue Jun 28 17:40:35 2022  | Hide | Hide all | Show all
vectfit_firstattempt.png
Attachment 2: TFSR785_28-06-2022_161937.pdf  37 kB  Uploaded Tue Jun 28 17:40:48 2022  | Show | Hide all | Show all
Attachment 3: enclosure_open.MP4  1.407 MB  Uploaded Tue Jun 28 17:46:35 2022
Attachment 4: enclosure_closed.MP4  879 kB  Uploaded Tue Jun 28 17:46:45 2022
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