Hanafi view: each testimony is pronounced twice at the prescribed volume, without an additional quiet-then-loud repetition.
Shafi‘i view: tarjī‘ is a Sunnah manner of adhan, supported especially by the account in which Abu Mahdhurah was taught the call, including quiet and loud testimonies.
Hanafi reasoning: the well-known adhan of Bilal did not include tarjī‘, so the extra repetition is not adopted in the standard Hanafi sequence.