Apple - How do I turn off the text tone swoosh when sending text messages?

Although it's not exactly what you might be looking for, if under Settings / Sounds / Sounds you set Text Tone to None, no sound will me made, neither when receiving nor when sending a Message.

I turned the default sound to just vibration, which turns off the swoosh sound and put personalized text alert sounds for individual people so I would be able to hear their incoming messages.