George Spanos has published a great article about recording wish, whiz, and zing by sounds.
Loading up a slingshot with various metal pieces and washers can definitely be a dangerous experiment in sound design. However, if done right, you can definitely obtain some great swish, whiz, and zing by sound effects which can be used as part of bullet impacts and as projectile whiz-bys. This can lead to greater player immersion within your games, and also provides a sense of reality and of utmost danger. The sound of a red-hot bullet impacting the ground near the player will surely make him/her aware of the imminent danger that the game currently calls for.
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