when I listen to voice messages (WhatsApp) I find the vibration annoying (at a rate of one per second): how can I turn it off?
The same problem while syncing WhatsApp: a vibration for those minutes…
I’m not sure if I fully understand your problem.
Do you mean the notification vibration, or are describing random vibrations?
Notification vibrations: during all the listening I have vibrations and sounds together
From other messages dropping in or from simply playing the message?
simply playing the message
Welcome to the forum and nice Avatar by the way, but I’m of no help regarding your issue. 
Did you check WA forums?
Which OS are you running? Settings>About>Build number
Hi there,
I am new to the Fairphone family, bought the FF4 a few months ago and have been having the same issue from the start : the phone vibrates every second when listening to audio (and when WhatsApp is backuping).
I found a solution on a WhatsApp forum for Samsung :
Long press on the WhatsApp icon. Press ibutton / Notifications, and deactivate Media Playback
Hope it might help some other users