I don't know if this is intended behaviour or not, but I'd class it as undesirable behaviour, so to my mind it's a bug, anyway..
I was playing around with the spoken messages settings (The Arch Linux espeak installation gives you a LOT of accent/pronunciation voices to choose from - Ms "kannada" can even pronounce 'identification' and 'buoy' correctly! ) and I noticed something strange..
Volume settings in the F2 options do NOT affect the volume of spoken voices.. even with the sound turned way down, the voice messages were still blaring at full volume. Definitely not what one would want to happen if having a quiet game at 2am while the spouse was sleeping!
Tested and confirmed so far with 1.77.1 64-bit on both Mint16 and Arch Linux.. I'll check Win and Mac when I get a chance..
Most games have some sort of paddling-pool-and-water-wings beginning to ease you in: Oolite takes the rather more Darwinian approach of heaving you straight into the ocean, often with a brick or two in your pockets for luck. ~ Disembodied