It is not uncommon for newborns to have varying reactions to loud noises. While some newborns may startle or react visibly to loud sounds, others may appear unfazed or not react at all. This can be due to the immaturity of their auditory system and the fact that they are still adapting to the outside world. However, if you consistently observe no reaction to any sound or have concerns about your newborn's hearing, it is advisable to consult a healthcare professional.