The loud and high-frequency barking of dogs represents the assertion of territorial sovereignty and the display of aggression; the short-term and high-frequency barking of dogs warns the same kind of danger; the crisp barking of dogs expresses greetings. A dog screaming suddenly may mean that it is in pain.

Observe your dog’s barking carefully to identify different situations

Loud, high-frequency barks indicate territorial claims and aggression.
Short, frequent barks signal warning of danger to similar species. May be accompanied by ferocious roars.
A clear bark indicates greeting.
A high-pitched bark indicates pleasure and friendliness.
A sudden scream indicates pain.
A low bark also signals a warning.

Dog Growling

Growling from a strange dog may be scary, but not every growling is aggressive. Dogs may also growl at loud noises. However, you should be wary, because even if it roars in excitement, it may accidentally bite someone, so don't get too close.
A low growl serves as a warning and to declare territory.
A low growl followed by a short bark is a response to a threat, and it may bite.
Medium-pitched growls and barks indicate nervousness and possibly aggression, so be careful.
A low, sustained growl indicates anxiety or suspicion.
A low grunt indicates contentment, while a gentle growl indicates playfulness, and should be judged in conjunction with other actions. Playful growls are often accompanied by excited barks.

Distinguish between whining and whining in dogs

Like the several kinds of barking mentioned above, whining and whining also have different situations.
Short whines and barks indicate curiosity and excitement.
Short whimpering indicates fear and nervousness.
A low whine indicates anxiety or submission.
A sustained, high-pitched whine is intended to attract attention or express pain.