From Rivendell Wiki
Before you start loading any audio onto a new system, you need to make a choice of what sample rate you are going to use. If you haven't already made a decision, the time for this choice is whilst you are configuring the server and workstations. Why should I do this you may be asking. Why can't I choose later on once I have everything up and running. Well, it would be worth looking at the reasons for using 44.1k or 48k sample rates.
44.1k is the sample rate that is used on CDs and most mp3s. It's history lies in the early days of digital audio and has been widely adopted within the domestic audio market. All the CDs that a broadcaster may use will be at a sample rate of 44.1k.
48k is used by DVB, DAB, and a lot of other broadcast standards. It's been adopted as the minimum standard for the film and TV industry, and domestic DVDs have their audio encoded at this sample rate. Most professional systems will by default be set to a sample rate of 48k.
By making the correct choice of sample rate to use at the start, you will save yourself a lot of grief later on. This might be now or in years to come. Changing the sample rate of an existing library is not a straight forward task and will take many hours of work. Differing sample rates do NOT mix within the library and trying to play back an audio file that is not at the correct system sample rate will result in failure. (The exception to this is the Audio Science ASI6xxx soundcard range that can cope with differing sample rates).
When importing audio into the library, Rivendell will convert all of the audio to the sample rate that has been set within the System-Wide Settings page of RDAdmin. It therefore does not matter if the audio to be imported is not at the same sample rate as system has been set to as when it gets to the library it will have been correctly converted.
From my experience in the UK, using a sample rate of 48k is the way to go. It is the sample rate used with all of the digital broadcast platforms in the UK (DAB, Satellite and Terrestrial DVB). With audio at 48k, there is no need to convert the sample rate before it is fed into a broadcast encoder.