Unfortunately I've tried sending the appropriate commands to turn off the sounds and nothing works. Any ideas?

See the Full Testing Example

The following binary commands are documented here.

• Startup

uint8_t wakeup_cmd       = 0x00;

 Serial2.begin(
        9600, SERIAL_8N1, 22,
        19);
 Serial2.write(wakeup_cmd);

 delay(50);

• Startup "boot" sound (still makes startup sound)

uint8_t bootSoundProhibit[]   = {0x08, 0xC6, 0x04, 0x08, 0x00, 0xF2, 0x0D, 0x00, 0xFE, 0x27};

Serial2.write(bootSoundProhibit, sizeof(bootSoundProhibit));

• Detection sound (still makes detection beep)

uint8_t prohibit_prompt_sound_decode_mode_cmd[]  = {0x07, 0xC6, 0x04, 0x08, 0x38, 0x00, 0xFE, 0xEF};

Serial2.write(prohibit_prompt_sound_decode_mode_cmd, sizeof(prohibit_prompt_sound_decode_mode_cmd));

None of these are changing the sounds in the example I posted.
Any help would be appreciated. (Beep sounds are not liked while
in a quiet museum for example).

thanks,