XA2 microphone noise issues [answered]
I acquired a refurbished Xperia XA2 dual SIM (H4113). As per the installation instructions (https://jolla.com/sailfishx-linux-instructions-xa2/), I toyed around with Android to ensure that everything works alright. Yet, if I record a video (no matter what FPS setting or resolution), during playback there is a distinct high pitched noise over the full length of the video. I'd say it's comparable to what a built-in microphone in a laptop pics up, if a fan is spinning. Before going ahead to flash Sailfish X, I wanted to rule out that it's a hardware issue, that I need to send the phone back for. Did anyone here experience the same issue, when still running Android?
EDIT: According to zuyev's answer I recorded a number of short audio sequences using https://f-droid.org/en/packages/com.github.axet.audiorecorder/, as I only have the F-Droid repositories available. In Audio Recorder the only settings I changed, were the Sample Rate and Mode, which are reflected in the file names.
Also, to clarify: I am still running the Android the XA2 came with. I did test recordings before and after applying the latest OTA updates. (No changes in audio quality.)
The high pitched noise, to my ears, is only noticeable in the stereo recordings.