What bitrate is needed to sound like analog FM?

As it turns out, 300 kbp/s or greater.  At least in critical listening environments according to the paper titled Perceived Audio Quality of Realistic FM and DAB+ Radio Broadcasting Systems (.pdf) published by the Journal of the Audio Engineering Society. This work was done by group in Sweden and made various observations with different program material and listening subjects. Each person was given a sample of analog FM audio to listen to, then they listened to various audio selections which were using bit reduction algorithms (AKA CODEC or Compression) and graded each one.  The methodology is very thorough and there is little left for subjective interpretation.

In less critical listening environments, bit rates of 160-192 kbp/s will work.

I made a chart and added HD Radio’s proprietary CODEC HDC, which is similar to, but not compatible with AAC:

System Codec Bit Rate (kbp/s)
HD Radio FM; HD1 channel* HDC (similar to AAC) 96 – 144
HD Radio FM; HD2 channel* HDC 24-48
HD Radio FM; HD3 channel* HDC 24-48
HD Radio AM* HDC 20-60
DRM30 (MF-HF) AAC/HE-AAC 34-72
DRM+ (VHF) AAC/HE-AAC 700
DAB+ AAC/HE-AAC 32 – 128
DAB MPEG II, Dolby digital 192 – 256
Blu-ray PCM** ≥6 Mbp/s
DVD PCM, DTS, Dolby digital >800
CD-A PCM 1,411
Web Streaming MPEG I,II,III, WMA, AAC, etc 32-320, 128 typical
iTunes AAC 128 – 256
Spotify Ogg Vorbis 96 – 320
Wimp AAC/HE-AAC 64 – 256

*Hydbrid mode
**PCM: uncompressed data

This is the composite Mean Basic Audio Quality and 95% confidence intervals for system across all excerpts:

digital-analog-audio-compar

Over the years, we have simply become accustomed to and now accept low quality audio from mp3 files being played over cheap computer speakers or through cheap ear buds.  Does this make it right?  In our drive to take something good and make it better, perhaps it should be, you know: Better.

Special thanks to Trevor from Surrey Electronics Limited.