Are you sure that the sound coming from Under the Hood and not on the brakes caliper piston? Sometimes its the friction between the back plate of the brake pads squeezing from the pression of the piston ring. On the next brake change, purchase some 'Brake Quiet paste' and apply them on the back of the brake pads frame.
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I also suggest to get investigate with an mecanical technician. Sometimes, the sound comes from a different place that expected.
Are you sure that the sound coming from Under the Hood and not on the brakes caliper piston? Sometimes its the friction between the back plate of the brake pads squeezing from the pression of the piston ring. On the next brake change, purchase some 'Brake Quiet paste' and apply them on the back of the brake pads frame.