Remember that ovens tend to make noise when in use, especially older models. The metal inside the oven expands when the oven warms up and contracts as the oven cools, which may cause a ringing or dinging sound as this happens. If the noise is short-lived and quiet, the sound may simply be part of normal operation.
Sometimes the problem is as simple as vibration of the oven against the surrounding cabinets or other material. Look to see if the oven is rubbing against nearby surfaces. Contact the oven manufacturer or another qualified installation professional if the oven does not seem to be installed evenly or is not level. If the gas oven is a range and you can reach the legs, set a construction level on the top surface when the surface is cool and adjust the legs until the bubble is centered in the level window.
The electric oven control, or EOC, uses a low voltage transformer to operate correctly. If there is a problem with either the transformer or the EOC, professional service is needed to inspect and replace the defective part. Contact the oven manufacturer for assistance.
On older gas ranges without an EOC, the ringing noise usually comes from the electro-mechanical timer and clock on the unit. Listen closely to the clock and timer area on the range and if the sound gets louder in this area, the components behind the clock and timer are probably to blame. Call the oven manufacturer for assistance.