data availability update

Audio_data/data_availability_statement.md

 # DATA AVAILABILITY
 
-Audio wavefiles contain DOLPHINFREE signal, which is proprietary. 
-Raw audios are therefore not available.
+Most audio wavefiles contain the DOLPHINFREE signal, which is confidential. Audio recordings that do not contain this signal are available upon request.
+
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+Contact [Loïc Lehnhoff](mailto:loic.lehnhoff@gmail.com) or [Bastien Mérigot](mailto:bastien.merigot@umontpellier.fr).
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