Inspect test and diagnose in sequence is key to avoiding unnecessary work and expense!
Does the noise change with the air con on? Or Head lights on? or Power steering operating?
Are the belts noisy, dry or slipping? Sitting low in the pulley grooves loose & worn out?
Identify the specific noise source;
- Use a water spray bottle to momentarily dampen each belt one at a time while listening for any significant change in the noise?
- Have a competent mechanic use a stethoscope to listen to the running bearings of the alternator, water pump, power steering pump, and air con compressor. Warning note, this is a hazardous operation not suitable for the DIY amateurs. Get a competent mechanic to do this part of the diagnosis!
Enjoy happy hunting/diagnosing