I've just bought Ulefone Armor 33 Pro, the one with two screens and a big loudspeaker on the back. And that rear loudspeaker sounds weird. 😣

It sounds as a bad audio-anticompression: as if the phone tries to amplify loud sounds even more, but with a delay of 100-200 millis. That noticeably changes the volume of the music all the time in the middle of the track.

NOTE! It only happens for the big rear loudspeaker. Everything sounds smooth when I play the same track through the headphone speaker (I used the Earpiece app).

It's easy to reproduce in a few minutes: construct a test file in Audacity, play it from a mobile phone, record the sound and compare.

What I've got looks like this:

https://preview.redd.it/4vne65nd1jjh1.png?width=1457&format=png&auto=webp&s=c048e418009deff0074ff1d375822ac718a4c3fb

Am I the only one with this problem? Or is that some known Ulefone "feature"?
Can it be fixed somehow?
Any ideas welcome!

PS: Audacity step-by-step if someone wants to try it too:

1. Open Audacity;
2. Generate/Tone: Sine, 440 Hz, amplitude=0.8, duration=0.5s;
3. Skip to the end (the "End" key);
4. Generate/Tone: Sine, 550 Hz, amplitude=0.2, duration=0.5s;
5. copy that several times: Ctrl+A, Ctrl+C, End, Ctrl+V, End, Ctrl+V, End, Ctrl+V, End, Ctrl+V;
6. Select/All; Track/Mix/Mix and Render; File/Export Audio: to computer as a .wav file (defaults are fine: Mono, 44100Hz, 16bit PCM).

Transfer the file to the mobile phone and record its playback:

1. Press "Mute" button on that test "Audio 1" track.
2. Tracks/Add New/Mono Track; Skip to start ("Home" key);
3. "Audio Setup" button : Recording Channels = 1 (Mono)
4. Press Record("R"); play the "test wav file" on the phone next to your mic; Press Stop;
5. Select/Region/Track Start to End (or double-click in the middle of the recording); Effects/Volume and Compression/Normalize: Apply.

Optionally repeat the same through Earpiece:

1. Press "Mute" button on the "Audio 2" recording;
2. Tracks/Add New/Mono Track; Skip to start ("Home" key);
3. Enable playback through Earpiece on the mobile phone;
4. Press Record("R"); play the "test wav file" on the phone; Press Stop;
5. Select/Region/Track Start to End (or double-click in the middle of the recording); Effects/Volume and Compression/Normalize: Apply.