Why phone systems are so picky
Phone lines have traditionally carried speech at 8,000 samples per second (8 kHz). Many phone systems therefore expect audio files in exactly that format, often with a specific encoding. A regular music MP3 or a high-quality studio recording does not fit: the system rejects the file, or converts it poorly.
The three families
- 8 kHz WAV with µ-law or a-law encoding: the classic telephony formats. Cisco, NEC and Mitel, among others, ask for these.
- Plain WAV (16-bit PCM): common with systems such as 3CX and GoTo Connect.
- MP3: many modern cloud systems, including RingCentral, Vonage, 8x8, Grasshopper, Ooma and Microsoft Teams, simply accept an MP3.
This breakdown comes from our catalogue of fourteen phone systems, each checked against official documentation, with the source listed on our phone system pages.
Do these problems sound familiar?
- The file is rejected at upload: the system expects a different encoding or container format.
- The message sounds tinny, distorted, too fast or too slow: the file has a different sample rate than the system expects.
- Converting it yourself with an online tool seems to work, but the result still fails: both the sample rate and the encoding must match exactly, and that is precise work.
How to never think about this again
With Meldstem you select your phone system while ordering. You then automatically receive the right file for your system, with a readme telling you which file to use and where to find the official upload instructions. If your system is not listed, choose "other" and you receive all formats at once.