Pacific Treefrog sounds range from quiet to very loud! The males vocalize to establish territory, and also to attract females. Once they get going it's called a chorus.
Tune into KRCB.org (104.9 FM Sonoma County) to listen for the current segment. Ear to the Wild is a short interstitial segment aired somewhat randomly throughout the day between other programs. They use shorts and postcards to fill airtime during breaks from Morning Edition and All Things Considered. Also during their music programing, as needed. Greta Mart tends to air them during her show around 4:47 or 5:47.
Check out these links for more information about Pacific Treefrogs:
Oregon Fish and Wildlife: Pacific Treefrog
USGS: Why are amphibian populations declining?