S9+ case vibrates when playing audio?

[Android Central Question]

Hi. I just wanted to check this is fairly normal as I just got my handset. When playing audio or videos with audio, the back of the phone has a noticeable vibration, more so if holding in portrait mode. I know the speaker is more powerful but I wanted to check this is a regular thing?

 

[andreapontic]

Hi, I have your same phone for a few days and I also noticed this thing, when the volume is at maximum, video or music that is, the low back near the speaker vibrates, I feel the vibration with my hand. I thought it was a defect, I think it's normal at this point