The short whistle sound you hear when shifting transmission in fast cars is often referred to as a "turbocharger blow-off valve" or simply a "blow-off valve" sound.
A blow-off valve is a device installed in turbocharged or supercharged engines to release excess pressure built up in the intake system. When you abruptly release the throttle or shift gears, the turbocharger or supercharger continues to build up boost pressure even though the throttle plate is closed. This excess pressure needs to be vented to prevent damage to the turbocharger and associated components.
The blow-off valve is designed to open at a certain pressure threshold, allowing the excess compressed air to escape from the intake system. As the air is rapidly expelled, it creates a distinctive whistle or "whoosh" sound. This sound is often more pronounced in high-performance or modified vehicles with aftermarket blow-off valves or tuned intake systems.
The blow-off valve sound has become a recognizable characteristic of turbocharged cars and is often associated with their performance and sporty nature. It adds to the overall auditory experience and can enhance the sensation of power and speed when driving.