Yes, Australian Shepherds bark a lot. They are vocal dogs, and, like most dogs, they tend to bark when playing, at loud noises and intruders. However, they can be discouraged from  
excessive barking  with proper training and exercise.
One way to curb excessive barking is by teaching your Aussie the “speak” and “quiet” cues to let them know when it’s appropriate to bark. Keeping their bodies active and minds stimulated with plenty of exercise can also reduce their tendency to bark.