Hello QC35 user,
Welcome to the Bose Community!
I'm sorry to hear you are having issues with your headphones. A screeching sound can sometimes occur if a feedback loop is created by the noise cancelling microphones interacting with the earcup's speakers. This rarely ever happens and is more likely to occur if the cushions are not attached correctly or are deteriorated. If this is what is happening, please try to remove the cushions and then re-attach them to see if the problem persists.
If the cushions are worn, you may need to purchase replacements. These can generally be picked up on the Bose website or by reaching out to local support. Fitting replacement cushions is simple to do, details can be found here. If the cushions are not an issue, please speak to local support in your region to discuss your options for service.
Be sure to let me know how you get on!
All the best,
Jeff G - Community Support
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