Praying Salatus Salaam is indeed a great act and worthy of praise. However, it carries a different ruling to being physically in front of the Prophet of Allah (i.e. in Madinah). The command is not to raise you voice over that of the Prophet in coversation and in personal prayer.
When we send the Durood on the Prophet then one should imagine that he is in front of them and can hear them , but at the same time you are asking Allah to send His Prophet blessings. This can be done loudly or quietly and both will be accepted and are allowed.
There are many evidences of this and Imam Suyuti has written a whole text on this issue alone.
May Allah give us the ability to continue sending Salams on His Messenger day and night, from near and far.
Allah knows best
[answer provided by: Muhammad Salim Ghisa]