I've had previously set a redstone system in version 14w26a to use commands like:

/playsound fireworks.blast AURAvulpes ~ ~ ~ 1 1.4

This played the sound relative to the player in 14w26a with a clock that ran command blocks testing for my "Sprinting" score, when i updated to 14w26b it plays relative to the command block rather than the player.. so if the player isnt in audible range when the command is run, the player doesn't hear the sound at all..

But when the [minimumVolume] is added (this sets the volume of the sound playing to the player)

/playsound fireworks.blast AURAvulpes ~ ~ ~ 1 1.4 1

Then the sound is played to the player at the volume set in [minimumVolume] But the sound is still played relative to to command block at the volume set in [volume] Which could mean that the sound is being played in two places (i cant test if this is true because I'm in singleplayer)

This bug can be re-created by:

Setting 1 command block with a /playsound command like: /playsound random.fizz @a ~ ~ ~ 1 1
and a way of activating the command from great distance (A path of redstone with repeaters, testfor commands with a clock, etc.) activating this command when at a great distance away (more than roughly 100 blocks) will show the sound wont play relative to you, only to the command block itself.. If you stand near it and activate it it will play relative to the command block, now edit the command to make it run /playsound random.fizz @a ~ ~ ~ 1 1 0.2
activate it from a great distance like last time and it will play at a volume of 0.2 relative to you, but if you activate it while near the command block, it will still play at a volume of 1 relative to the command block..