95 Aurora Ignition "Buzz"

[RLT]

I have a '95 Aurora with 156K miles. The last few weeks I've had occasional problems starting the car. Sometimes when I turn the key I hear a Buzz & it will not turn over (sounds kind of like something you'd hear after giving a wrong answer on a game show). It does not do this all the time but seems to be getting more frequent. I turn the key off wait a couple seconds & try again -- recently I've had to do this as many as five times . . . so far it has always started. Each time when it does finally crank it has indications of a strong battery & all seems well . . . could it just be that my battery is getting weak? I've had the car about four years - I've not replaced the battery since I've owed it and am not sure when it was last replaced.

Any ideas as to the cause/problem greatly appreciated.

Thanks,
Rob