The Braun ThermoScan 7 (ear) with product ID IRT6520B actually has a function that beeps when a measurement is taken to confirm correct positioning. This function is provided by the ExactTemp system, which uses a light and a beep to indicate that the measurement has been taken correctly.

If your thermometer no longer beeps, it could be that the device is faulty or that the function has been disabled. It would be advisable to consult the instruction manual or contact the manufacturer to check this.