Double Red Coin Sound Glitch
The double red coin sound glitch is a glitch in the Japanese version of Super Mario 64. As the name implies, the glitch causes the sound played when collecting a red coin to be played twice.
Explanation
Certain objects that need to play a sound spawn an object known as a sound spawner to play that sound. These include the breaking sound for breakable walls, the sound of falling pillars hitting the ground, and, in the Japanese version, the sound from a red coin being collected. For red coins, after 30 frames the sound spawner unloads and this sends a signal to stop playing the sound, cutting it off if it is still playing. However, if the sound spawner unloads within the same frame that the sound finished, the signal to stop playing is instead interpreted as a signal to start playing the sound. In the case of the red coin sound, the sound actually lasts for 1.2 seconds but is silent after 30 frames making the cutoff unnoticeable. With the right amount of lag the sound spawner despawning can be delayed so that the despawn occurs on the same frame as the sound ending, which causes the sound to play again. In US and later versions, this does not occur.