ulaw file plays as static

I have hundreds of files that are .ulaw format and when I try to play them it just sounds like static. I have attached the MediaInfo output showing the technical details of the file type. These files were generated with an ancient system that has had a technical failure and can no longer play the files. They are simple audio files. One interesting thing about them is that they should be much longer than they’re saying they are.

I downloaded Audacity, used Import>Raw Data>encoding U-Law>sample rate 8000 Hz. I found these recommendations on the internet and that’s why I downloaded Audacity. It didn’t work. I’m hoping I’ve done something wrong and someone here can steer me right. Perhaps something to do with compression?

I have little experience working with audio files, so plain English would be great :slight_smile:
audio data.PNG

One interesting thing about them is that they should be much longer than they’re saying they are.

I don’t know but that might be a clue.

An 8kHz sample rate x 8-bits is a bitrate of 64kbps, so at least MediaInfo agrees with itself. And as you may know, there are 8 bits in a byte so the file size should be 8000 bytes per second (if MediaInfo is telling the truth).

And, 8kHz/54KB is 6.5 seconds.

…If the playing time is actually longer than that, the bitrate is lower than indicated. If it’s uncompressed, the true sample rate is less than 8kHz and/or bit depth is lower than 8-bits.

Just for the heck of it, try GSM 6.10 instead of uLaw. It has a lower bitrate (so longer playing time for a given file size).

Audacity can import standard CCITT u-law files as normal audio files. “Import RAW” is only required if the files are “headerless” (raw data rather than properly defined WAV files).

There is a u-law test file here: https://forum.audacityteam.org/download/file.php?id=3047
Audacity should be able to import this file correctly with normal “Import > Audio” and it should sound like a slightly distorted 440 Hz sine tone.

If you are able to import this test file correctly, but not your files, then there’s something wrong with your files.

thanks so much for your responses! I tried a couple of things.

-import raw data>ULaw>Mono>8000 Hz - plain static 6.6 seconds (this is what I was doing before)
-import audio - plain static 6.6 seconds
-import raw data>GSM6.10>Mono>8000 Hz - distorted tones almost no static, 32 seconds - I feel like this one is on the right track but not quite there?

I was able to download and do a plain import of the test u-law file, I don’t know what a distorted 440 Hz sine tone sounds like, but the file played and just sounded like a solid tone, quite soothing actually lol.

any further things I can try?

[u]Upload/attach[/u] one of the files and maybe someone here can figure it out.

unfortunately due to the nature of the recording I am unable to provide it. I know it would help tremendously but it’s not possible.


I’m sorry to hear that you were unable to open and play-back your files. I just created an account to say thank you, as your issue and the recommended solutions help me open listen to some .snd audio files using the import option in audacity, any other player wasn’t able to play back the headless audio.

I had to find out how the file was converted into a headless .snd file and I was able to import it to audacity and play it back

my audios are encoded as follows.
raw, mu-law (u-law), mono, 8-bits per sample, 8KHZ sample rate.