There are 2 kinds of analog speaker noise that might happen due to power_save ( issue 775486 ):

1. pop/click sound when device is opened/closed. There's a timeout setting so the pop sound happens after #timeout seconds after device is closed.

2. A hum noise keeps coming out from speaker. This happens when the device is not in use.

The user states "I am using an "old" Dell speaker bar which mounts under the monitor", and no specific model is referenced in the bug.
I'll have such powered analog / audio jack speaker(s) be used in FullRelease testing, and reboot scenario should catch this. Having this is mostly a last resort manual verification - there should be a different type of test to check for the solution proposed in  issue 775486 , i.e leaving power save mode disabled on devices with no battery.

I'm also leaning towards not to add any manual testing because it doesn't scale. Is there any other idea of automatically testing?

I don't think that kind of noise can be picked up clearly by chameleon
microphone. If speaker volume is not turned loud enough, it is like
background noise. If speaker volume is turned too loud, it might break
current internal microphone test.
Also, we don't know disabling power save mode leads to this kind of noise
until user reports.

Since we already have headphone test in the manual verification, replacing
headphone with 3.5mm speaker, or adding 3.5mm speaker for Chromebox seems
to be a reasonable effort.
Thanks!

I talked to Jimmy. If we want to test this automatically, we need a box that can shield the noise from the environment. Before we have it, let's cover this in manual testing.