In the Sound control panel, there are various sub-panels. Clicking on the Alert Sounds pop-up menu will bring up the choices Alert Sounds, Sound In, Sound Out, and Volumes. The volume control in the Alert Sounds sub-panel controls the volume of alert sounds (error beeps). In the Volumes sub-panel is the system volume control. It defaults to 50% volume which, even so, can be quite loud. If you lower that volume, all sounds will be scaled down in volume, including the startup sound.
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If you do not want the startup sound at all, but you do want other Macintosh sounds, you can set an environment variable TB_NOSTARTUPSOUND to 1 and no startup sound will occur.
Otherwise, if you want no sound at all, you can set TB_SOUND_OFF to 1 (or add command line option -nosound) and MAE will be silent with the exception of using the standard XBell() for Alert sounds.
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