AMR is short form of Adaptive Multi Rate. This is an audio codec which is used as audio compression format. This format is optimized especially for speech coding.
This format supports narrow band, multi rate signals received at variable bitrate which can vary from 4.75kb/s to 12.2kb/s. This format is considered to be standard speech codec by 3GPP and now this is format is mostly used in UMTS and GSM. The speech recordings stored by many mobile devices use AMR format to store audio data. This format is a 3GP container format which is based on ISO standard for media file format.
In addition to the problem described above, i.e. the lack of the appropriate application to support the .AMR file, there may be several reasons that cause problems with opening and operation of the data format:
A quite common problem is the lack of application in the appropriate version. Even if you have an application, with the help of which you should open the .AMR file, you may have a problem with it because of its version. Perhaps in previous versions the application has not yet supported the .AMR file, so download the update and check again.
If you have already installed the appropriate application, and it is the correct version, the file may not open correctly, because the operating system does not have information that this program supports the file. So you need to "show" which program the computer should use. To do this:
It also happens that the file you want to open is corrupt and therefore there is no such possibility. In this situation, you should find its different version, or ask a person from whom you got, to send it again.