Signal android app doesnt make sound when receiving a notification

REPRODUCIBILITY (% or how often): allways
BUILD ID = OS VERSION (Settings > About product): 4.2
HARDWARE (XA2, X10, X10 II, …): x10 II
UI LANGUAGE: english
REGRESSION: (compared to previous public release: Yes, No, ?):

DESCRIPTION:

when receiving a notification from siganl android app , the phone doesnt make any sound

PRECONDITIONS:

STEPS TO REPRODUCE:

  1. signal ready to receive messages
  2. receiving a sms from another user in signal
  3. phone doesnt advice with a sound notification

EXPECTED RESULT:

that a sound for a notification is heard

ACTUAL RESULT:

no sound for a notification

ADDITIONAL INFORMATION:

(Please ALWAYS attach relevant data such as logs, screenshots, etc…)

Is Android allowed to run in the background?

yes, it is allowed to be in the background