water heater is making very strange noise

[mlb3c]

I turn on the hot water and the water heater starts to hum...sounds like Johnny Cash singing I walk the line....very unnerving. Only happens with the hot water....I've never encountered anything like this. It wouldnt be so bad, but I'm not a big fan of Johnny Cash and I need to use the hot water. Any suggestions as to how I can make this stop...or perhaps I can change its tune?

 

[Nige F]

Lonnie Donnegan singing "The Rock Island Line"..........."I got pig iron...OLE pig iron".........Classic.....Maybe the washer in your faucet

 

[racket]

I would get nervous when it starts humming "Ring of Fire"

 

[Nige F]

I would get nervous when it starts humming "Ring of Fire"

Strange.I thought I heard that coming from a manhole outside the Curry House the other day