The sound of a car running in an MP3 audio file can be described as the powerful sound of a running engine, the sound of tires sliding on the road, and the sound of wind blowing through the glass. The engine sound is often regular and rhythmic, showing the strength and stability of the vehicle. Tires make a gentle and continuous sound as they make contact and slide across the road surface. The sound of wind brushing through glass can create a soothing sound, bringing a feeling of comfort and connection to the surrounding environment. Overall, this sound creates a unique and multi-dimensional audio experience of driving a car.