No more sound played when using external monitor

OS: Win10 Pro
PsychoPy version: 2024.1.0 and 2024.1.4
Standard Standalone? (y/n): yes

An experiment that worked well in PsychoPy v2023.2.4 suddenly gives us a head-ache after an update to 2024.1.0, specifically for sound when the experiment is run on an external monitor. We noted a number of bugs with reaction times in 2024.1.0 and further updated to 2024.1.4 but the sound issue remains.

Here is what is wrong: The experiment behaves well overall, except for sound. Without the ext monitor attached all is perfect, all sounds play. When the ext monitor is attached, no sounds play. This problem never occured in v2023.2.3 where the task was developed, and it started with v2024.1.0 and remains in v2024.1.4.

We made sure the problem is the monitor since the problem only ever arises when it is attached. The task runs through without any errors and or warnings given out due to sound problems.

We made sure sound behaves well on this machine with and without an ext monitor outside of PaychoPy and all works perfectly. The issue is limited to sound through PsychoPy.

To make sure the problem is not caused by anything in the experiment that is not directly related to the sound issue, like some code snippets, or the (reading of) audio files, we created a new plain experiment that consists simply in playing a single pure tone sound generated in PsychoPy by defining a sound routine with duration 1.0s and Sound = A. We reproduce the problem above.

Changing “device” in the sound routine does not help. Changing the audio library pr latency prio in the global settings does not work due to an Error that the other audio backends are not available and PsychoPy falls back to ptb.