Why do I hear a low humming noise from my 2005 Honda Accord after I had the air filter replaced The mechanic says that it is a small electric motor Honda's have that is part of the engine help?

The low humming on a 2005 Honda Accord could be one of several things. The most common source of a humming noise is a wheel bearing which may be coming loose. If the noise get louder over time the wheel bearings should be checked.