These two short clips contain the same three synthetic taps: soft, loud, then medium. Compare what you hear after each attack. Use a comfortable volume and keep it fixed for both clips.

1. Play both references once, then compare the sounds just after 0.45 s, 2.00 s and 3.55 s. The first 300 ms of each tap are identical in both versions.
2. Listen to the next half-second, especially after the first tap. In one reference the note fades naturally. In the other the quiet part of the decay drops faster. Try identifying unknown X from that tail, then repeat the comparison on another tap.
3. If you can hear a difference only when switching during an attack, replay from the start of that tap and listen through the end. Playback starts and peak levels match.

Both files are synthesized from the same tones. The alternate uses smooth gain attenuation below a threshold in the late decay. The tail is still present, just lower in level. No microphones or device recordings were used. This exercise isolates one kind of processing artefact. It does not characterize a particular recorder or noise-reduction feature.

To apply the check to a recording, make two short takes without changing mic placement, app or playback volume. Change only the input processing and listen after the last quiet syllable. For UltraMic X200, use the Alidel sound-mode instructions: alidel.kz/guides/x200-podklyuchenie-telefona to identify original sound and noise reduction and leave the reverb effect out of both takes.