Factorio Forums

Lab working sounds will also synchronise if the game is set to not automatically pause on finished research but you still manage to pause the game in that exact moment.

Description:
When the game is set to not pause after research is finished, if you open the technology screen (no queue) in the exact moment the research finishes and start a new research, all lab working sounds will synchronise and become loud. This however goes away after another pause cycle or if the research finishes next time.
Here is a video in which I demonstrate these issues with the "show-environment-sound-info" debug option enabled. There is also a weird dip in the lab sound volume at one point, I can't reproduce that.

What I expected:
Lab sounds are randomised, even if you open the technology screen frame-perfect.

What I got:
Lab working sounds synchronise if the technology screen is opened immediately after research finishes.

Steps to reproduce:
-> Lab working sounds synchronise

1. Also works best in god controller with show-environment-sound-info enabled
2. interface setting "Technology screen opens when research is completed" should be disabled
3. research queue should be disabled (might work with it enabled, not tested)
4. Find yourself some labs
5. if not already researching, start researching something, then resume the game
6. lab working sounds should play randomised ("progress boxes" show random progress)
7. open technology screen as soon as research finishes (could require frame-perfect input)
8. select a new research
9. resume the game
10. lab working sounds play synchronised ("progress boxes" all show same progress)
11. pause the game and resume it
12. lab working sounds are randomised again
13. repeat steps 7 to 10, so the sounds are synchronised again
14. wait until research finishes (no frame-perfect input this time)
15. start a new research and resume the game
16. lab working sounds are randomised again

Edit: split original post into two

Thanks for the exhaustive report. The issue is an incorrect interaction of working sound which is fading out and pausing the game (opening the technology screen).
With labs you have whole 20 ticks while the sound is fading out to pause the game and trigger this issue.
Note: this only happens with the SDL audio backend as Allegro handles fade out when pausing differently.
This is now fixed for next release.