M4R, iPhone Ringtone File (.m4r)
The M4R Audio file format
Used with the iPhone series of smart phones for ringtones, more people are using this file than they actually realize. It is basically an AAC or M4A file with a new name. Not all audio from the iTunes store support the creation of M4R ringtones. When M4R files (ringtones) are synced to an iPhone from a computer, the file is automatically transferred from computer to phone. Audio with this file extension can be converted from other forms, or purchased/downloaded as an M4R file through the iTunes store. These files, with their compression techniques, allow for smaller file sizes with limited perceived quality loss to provide the best ringtones possible for iPhones.
Technical details of M4R files
Further compression separates MP3 and M4R files. It is part of the MPEG-4 standard under the ISO-IEC standard 14495-3. The lossy compression algorithm is similar to the ACC and MP3 files, but M4R’s support auditory masking. This allows the compression to take place through the removal of data and audio which cannot be picked up and processed by the human ear. This means M4R files maintain the high audio quality without taking up large amount of space for such a function. Using the conversion of an audio file to M4R allows users to use any audio clip as a ringtone, alert tone, text tone, or alarm. This allows for high levels of customizability with the iPhone, assuming users know what files to use.