5.7.2 Field Recording Standards The same technical recording standards apply to field recordings as they do to archival transfers; i.e. they should be captured and stored in a widely used, standard linear audio file format, normally .wav or BWF .wav format; they should be created with a suitable sampling rate; at least 48 kHz, but, depending on intentions, possibly higher, either 96 kHz or maybe in some circumstances 192 kHz or higher. It is advisable to make recordings at 24 bit. Lower rates will not reflect the dynamic range of the performance and the environment in which the recording is made and could well result in low level signals of very poor quality. Whatever the recording resolution, it is advisable to record natively to a standard format. This allows direct transfer to archival storage without alteration of the format and simplifies the archiving processes. Using BWF facilitates the collection of critical metadata which is necessary to the life cycle of archival digital information. The use of data reduced (popularly called compressed) recording formats, such as MP3 or ATRAC encoding will produce recordings which do not meet archival standards. Data reduced formats, although highly developed, not only omit data irretrievably that would otherwise be captured by a non-data reduced format, but also create artefacts in the time domain as well as in the spectral domain. Such artefacts can lead to misinterpretations of spectral components as well as of time-related components, especially when analysing the signal by means of a spectral tool. The artefacts of data reduction codecs cannot be recalculated or compensated for at a post processing stage, as they are dependant on the level, dynamics and frequency spectrum of the original signal. For archival purposes it is advisable to re-encode the resultant files of compressed recording formats as .wav files (this is also the case with Minidisc,and early technology which used lossy codecs (See 5.6.10 Minidisc). While this does not replace the missing data, it does reduce further dependence on the codecs.