What are the early signs of a turbo failure?

Could you elaborate on the initial indicators that suggest a potential turbocharger failure? Are there any audible noises, such as whistling or screeching, that could be heard? Would there be a noticeable decrease in engine power or acceleration? Additionally, are there any visual cues, like oil leaks or smoke emissions, that could signal a turbo issue? Understanding these preliminary symptoms would be invaluable for drivers to promptly identify and address potential turbocharger problems.