General recommendations

• Always record and edit audio in a lossless format like WAV.
  
• Record in 24-bit samples at a 48kHz sample rate.
  
• Avoid applying heavy limiting and dynamic compression effects when creating your master.
  
• Keep peaks below -1 dBFS to leave headroom for different normalise and compression operations.
  
• Don't up sample to a higher rate than the original.

iono.fm Import process

• For uploading your audio into our platform, use a lossless format only if you are publishing music podcasts. When uploading lossless audio, please use FLAC instead of raw WAV files.
• Most podcast and voice content can use lossy compression without sacrificing quality. 
• We recommend compressed file uploads at 48kHz sample rate and encoded with AAC-LC at 160kbps.
• We distribute all files as stereo. For mono input we duplicate the audio channel to create stereo output.
• We perform EBU R128 perceptual loudness normalisation at a target of 16 LUFS. (Loudness Range 11 LUFS, True Peak limiting -1.5 LUFS)
• Low quality output formats downsample to 24kHz and 32kHz sample rates, while high quality output uses 48khz.

Additional links

• The Audio producer's guide to Loudness - http://transom.org/2015/the-audio-producers-guide-to-loudness/
  
  
• Mastering for iTunes - https://www.apple.com/itunes/mastered-for-itunes/