I found that there are two issues:

1. The play music app installation. From the log it seems that sometimes after adb install command, com.google.android.music is not listed in adb shell pm list packages.

This accounts for failure reason that autotest server is waiting for play music app to be ready.

2. When installation succeeds, we use intent to trigger playback:

        arc.adb_shell(                                                           
                'am start -a android.intent.action.VIEW'                         
                ' -d "file://%s" -t "audio/%s"' % (                              
                        pipes.quote(dest_path), pipes.quote(ext))) 

  However, there will be a window asking user to select chrome / play music app. We need a way to bypass that.

This accounts for failure reason that RMS is too low.

I will the solution of above two issues.

Note for myself:

To debug client side test, the log is in /usr/local/autotest/results/default/cheets_PlayMusicApp/debug/cheets_PlayMusicApp.DEBUG 

This is how I found installation failure.
The server side log is not helpful.

Hi Victor, do you know if it is possible to specify the preferred app for media file ?  Currently intent will let user choose which app is preferred between chrome and play music. Or, is it possible to select the preferred app through ui ?

Thanks!

Try adding "-n com.google.app/.Avcitity" to make it an explicit intent.

Thank you Victor!
After some testing I found that this is called audio preview.
Like this:
adb shell am start -a android.intent.action.VIEW -d "file:///storage/emulated/0/sine440.wav" -t "audio/.wav" -n "com.google.android.music/.AudioPreview"

I will upload a cl to fix this.
Thanks!

https://chromium-review.googlesource.com/446906 posted.
The test runs fine on my local setup.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/third_party/autotest/+/f4d7e760791a18c6375e2c878b5421515920d660

commit f4d7e760791a18c6375e2c878b5421515920d660
Author: Cheng-Yi Chiang <cychiang@chromium.org>
Date: Wed Mar 01 02:09:13 2017

[autotest] audio_AudioARCPlayback test

Fix the broken test.
- Increase the waiting time for android to be ready and app to be
  installed.
- Specify the activity to play audio file, otherwise, there will be a
  menu for user to choose between Chrome and Play Music app.

BUG= chromium:671105 
TEST=run audio_AudioARCPlayback test on kevin
Change-Id: Iaf0114e2038a2dd5c1e462118337994fa9da89a8
Reviewed-on: https://chromium-review.googlesource.com/446906
Commit-Ready: Cheng-Yi Chiang <cychiang@chromium.org>
Tested-by: Cheng-Yi Chiang <cychiang@chromium.org>
Reviewed-by: Wai-Hong Tam <waihong@google.com>

[modify] https://crrev.com/f4d7e760791a18c6375e2c878b5421515920d660/server/site_tests/audio_AudioARCPlayback/audio_AudioARCPlayback.py
[modify] https://crrev.com/f4d7e760791a18c6375e2c878b5421515920d660/client/cros/multimedia/arc_resource.py

The test result looks good https://wmatrix.googleplex.com/matrix/unfiltered?tests=audio_AudioARCPlayback.headphone&days_back=20&hide_missing=True

Let's monitor for some days and close this.

Triage nag: This Chrome OS bug has an owner but no component. Please add a component so that this can be tracked by the relevant team.

<UI triage> Bug owners, please add the appropriate component to your bug. Thanks!

The issue with the failing test is fixed. https://screenshot.googleplex.com/gxhK6fMFbNG
The outstanding failure on squawks is actually an infra error. I do not think the test should run on this board.