sound on iPhone 4s drops

[playdamusic]

Since I got the latest Spotify update (this morning) on my iPhone 4s, the sound drops away after about a minute of listening, on all apps and functions. Only phoning works. My iOs is up to date, as are all apps on my iPhone. Anybody else got this problem? By the way: I have rebooted my iPhone and reinstalled Spotify. Didn't help. All sound controls are at the normal position. I can make a phone call and my phone rings when I'm called.