Strange noises that were heard by readers in the Sopwell area may have been caused by workers carrying out maintenance work on the railway line.
Network Rail has confirmed that staff were changing sleepers, testing the rails and regulating the ballasts, which could have been responsible for the noises.
Resident Lee Tyler reported hearing the noise at about 2am yesterday morning.
He described it as similar to guitar feedback.
To hear a sound clip of the noise click here.
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