Three beeps immediately after powering up the board mean that the gyroscope calibration has completed successfully.
INAV (RubiQ 1.0, 1.5, or 2.0 QX7) and RubiQ Configurator (RubiQ 2.0 X9 Lite) calibrate the gyro automatically upon every power-up. It is important that RubiQ stay still until the three beeps sound, so that gyro calibration isn’t thrown off. If you move the drone significantly during calibration, the software will detect this, and will automatically restart the calibration once the drone is still again. This will delay the “three beeps” tone. If you move the drone just a little bit, the gyro calibration may be incorrect, and the drone may not fly correctly.
The tone heard at the end of the GPS search indicates 3D Lock has been established.