Welcome to the forum. I've also noticed occasional screeches appearing in content I watch, though it's only very infrequently. It could be a problem with the source content but it could also be corrupted traffic or signal blips. To start with try rebooting your broadband router and also when your TV and whatever device you use to watch NOW TV are powered down remove and reconnect the HDMI cable between them.
If you still notice issues after that, next time try noting down the time stamp you notice the sounds appearing and post back with the film title and times. It should then be possible to check if others get the same issue and if so get the NOW TV Team to look into it.
Those screeches that we all have noticed tend to happen when watching an animation show, I don't know about films, for example, I get the same screech in the same place, i.e. during the startup credits, on Acher and I've watched all the episodes.
I've also noticed that screech during Family Guy and American Dad but those noises do not occur when watching those shows on terrestrial TV.
So it seems these screeches are unique to Now TV and only, as far as I know, when watching an animation show.
@ukbobboy It's not just animation shows, I've noticed it on catch-up content and rarely watch animation, but as its a rare occurrence for me I've ignored it. If you watch a lot of animation and notice it that would tend to link the two together for you. If it happens in the same place for everybody and causes issues for people tho then it needs looking into. If you want to provide info on title, episode and time stamps that would be useful.
I was watching some catch up shows, between 11.30pm and 2.00am, and the screeches happened in all of them, I watched Strike Back, Archer and Nat Geo Wild.
Unfortunately, I could not "time-stamp" the screech in Strike Back or Nat Geo Wild because they occurred unexpectedly and when I was far too engrossed in the shows to remember to check. As for Archer, the screech happened, as I reported before, between 3 minutes and 3 minutes 30 seconds after the show started (during the walking legs sequence in the opening credits).
I know the above is not of much help in actually tracking down this "screeching" problem but it does reaffirm the problem does exist.