For a louder sound, you need to replace the standard air filter with a conical one. Simply changing the air filters won't make your car sound louder. To get that unique and satisfying sound, you need to replace the original air cleaner and air box with a conical air filter. This way, the air cleaner is widely exposed and you will hear a louder sound from the air flowing into the engine as you accelerate. The engine is essentially a big boat full of things that explode, and to make a boom, it needs to suck in air.
Car manufacturers do their best to reduce engine noise to a pleasant hum. This and other objectives are achieved by an intake box around the air cleaner (it also keeps the filter dry and free of excess grease and dirt, as well as separating it from the hot air in the engine compartment). In theory, high-performance air filters should make the engine sound louder because they increase airflow. Conical filters don't improve engine performance to a measurable level, and are actually better suited for custom installations where an airbox doesn't fit. Air filters are designed to filter out impurities and only let in air particles.
Although the cold air intake is marketed to increase power, the real beauty of the cold air intake is the unique sound it provides. However, there is another type of air filter that comes in the shape of a cone: they are larger and are much more exposed. Dust particles, flies, insects, sand - there are a lot of impurities in the air, and they should not enter the car engine. Instead of being made of paper, high-performance air filters, such as those from K&N, are made of foam, coated with oil. This can restrict the amount of air that can enter the engine and, theoretically, reduce performance.
Without the air box, the sound of air entering your car will no longer be muffled, providing you with a louder and more aggressive sound when you step on the accelerator. If you really want to have a noisier car with an air filter, you can choose to replace the air box and air cleaner with a cone air filter.