A super common critique is that the lack of real threats takes away from the horror. Now, adding in real threats probably breaks the point of the game a bit, but I have an idea for a threat that still keeps screaming as the noly killer.
The idea is that any scares, which are avoidable, you should try to avoid, because those "optional" scares will increase the sensitivity of your microphone, making the game harder if you don't play carefully. Players should obviously be told this in order to make it work and to not seem unfair to anyone unaware. Perhaps the bar that marks the scream volume can move to the left each, in order to act as an indicator.