A noise coming from a pull cord operated fan (with no remote controller) is often caused by something vibrating as it has worked slightly loose. If there is a light kit fitted then a buzzing or humming could be a glass shade, and a clicking sound can be caused by a blade screw working loose. Start by checking and tightening all the fixings so they are completely secure.
If the noise is still present then try removing any glass shades completely and take the blades and blade carriers off so just the motor alone is spinning. If this does not stop the noise then a faulty reverse switch or capacitor may be causing the problem. Replacements can be found in the SPARES section of our website.