Barking when no people are home

Hi All,

We live in a somewhat rural area.  A neighbor about 1/4 mile away from us said one of our two dogs barked for 3 hours when we were gone for the day.  We might try rigging up a tape recorder to make sure it is our dog. If it is, any suggestions?  She gets lots of exercise and attention, we have another dog and we rarely are gone for more than a few hours at a time.  She is a 2 year old lab that joined us about 6 weeks ago.

Thanks!