There are a lot available if you know where to look. But it also depends on the position of the gun with relation to the cockpit and, of course, whether you want the sound to be heard by someone on the ground or in a cockpit.
The F-4 I flew had a Gunpod on the centerline station and was heard as a low volume buzz. If on the ground when the airplane was strafing it was much louder and the pitch depended on where you were relative to the airplane because of Doppler effects.
It is the kind of question whose answer depends on a lot of factors.