Whistling noise - Peugeot Cars & Trucks

belt is likely worn, tensioner may be worn or idler pulley. i would replace belt first.

A whistling noise can be generated by an alternator at high RPM's and indicates a slip ring brush problem or a diode failing . It resembles a frequency whistle.. IT may also be from a leaking gasket and a partially blocked exhaust system from a failed cat converter and at speed and power, the exhaust gas is forced out the hole

Checking Window Seals - The window seals (weather stripping) in your car are used to seal the water and wind for entering the passenger compartment. When these seals fail from damage or are eroded by the weather they can allow wind noise to enter the passenger compartment. This failure can cause a whistling noise as the car is driven. Some noises are only present when the vehicle is driven at certain speeds such as 55 MPH. These whistling noises can be difficult to find since you are driving at the time. Have a passenger help with the diagnosis by running their hand along the area the noise is being generated from. Once the noise source has been located replace or repair the failed seal and recheck.

check the PCB balve maybe is cloged and the breather that create high vacuum wen are cloged and create a whistling sound.

usually a whistling sound is from a vacuum leak

Check the protective backing plate for the brakes to see if its bent. Look at the opposite side to get a good idea what it looks like to bend back into shape if so. If bent they will create a noise or whistle effect

you most likely have an aftermarket radio installed
the noise you hear is engine noise, if yo turn your radio off it will go away
this can be fixed by either getting better wiring for your aftermarket radio or by installing a noise filter, you can purchase that at most big electronic stores

Check your air intake manifold hose if is crack this cause whistle noise replace the hose.

try and look at the belts, if they are wore out replace them