When M4A files are encoded at low bitrates like 48kbps, they typically utilize . A specific feature of this technology is Spectral Band Replication (SBR) :
: At 48kbps, you can expect a high-frequency "roll-off" around 11–13 kHz , which is sufficient for clear voice and background music, though some "underwater" artifacts may be audible in complex tracks. 48kbps m4a(-1 B)
: You can store roughly four times as much audio compared to a standard 192kbps MP3 while maintaining reasonable intelligibility. When M4A files are encoded at low bitrates