According to this a barking dog can be up to 100 Decibels!!!
http://www.gothamgazette.com/article/iotw/20040712/200/1034
WHAT IS TOO LOUD?
If you have to raise your voice while speaking to someone three feet away from you, then your immediate environment could be hazardous to your health...
http://www.telegraph.co.uk/earth/countryside/6072263/Rowdy-rooster-set-feathers-flying.html
this one says just under 90 Db which makes sense because than he is only 10 Db more than a leghorn hen (and she is loud!)
Many of you are worried about how loud your hens are--for real not preferences.
Well I have how loud they are for real! Decibels measure noise. I bought a decibel meter at Radioshack and did a little bit of experimenting and I found this.
A leghorn hen at the peak of her egg song is: 78 Db...