It's not an issue with the device. It's because there's a speaker behind it. It's mildly annoying, though.
The straps on the tricorder are terrible, though. You WILL crease them. It just takes a few minutes of it resting a certain way for it to permanently crease. I've opted to use a velcro tie in order to keep the strap looped without forming sharp angles. However, if you let the strap ends (near the tricorder) rest at any angle that isn't going completely up, it WILL crease.
Fortunately the strap is removable (go watch the 'tear down' video on Youtube). So you can replace it if the creasing eventually leads to cracks in the fake leather. I would probably remove the strap as soon as you get it and store it curled up and use a custom leather strap for display/cosplay purposes.
The leatherette case is very nice, though.