Hella utilizes a combination of low tone (300Hz) and high tone (500hZ) disk-type horns to project a powerful 118dB sound. These horns are the go to replacement for the faint stock Subaru horns!
When a car goes past you, the pitch of the engine sound that you hear changes. Why is that? ... The train horn sounds with f=320 Hz. The speed of sound is v=340 m/sec. ...
AEM Intake Systems are designed to increase horsepower and torque gains as well as better engine sound when used as a replacement for the factory airbox and air filter.