All I can hear is dogs barking.

I need to know if the verb in the above sentence should be 'is' or 'are'
Anyone know? I have a dispute going with a friend. Thanks.

It's is.

The subject is "all I can hear" which is a singular.

This idea can be pushed even further:

Cows in a field is something you don't see too often.

In this example, "cows in a field" is the subject, but it's a single concept; therefore, is is correct.

Thank you Craig. We are in agreement.