Downloading SPLnFFTviewer 1.4 for Mac from the developer's website was possible when we last checked. We cannot confirm if there is a free download of this app available. The software lies within System Tools, more precisely File Managers. This free Mac application was originally developed by Fabien LEFEBVRE. We recommend checking the downloaded files with any free antivirus.
From the developer:
SPLnFFT Viewer is a companion tool for the iOS App "SPLnFFT Noise Meter". Data exported from iOS App to your Dropbox directory can be visualized here, and the input binary files are expected to be found at the default Dropbox location, though you can specify another directory. What is important is to confirm the location ("Open") to allow read/write to this directory.
You may want to check out more software for Mac, such as pdf-FieldMerge or Catenator, which might be related to SPLnFFTviewer.