Free online ULAW to WAV converter

What the ULAW format is

ULAW, also written μ-law or G.711 μ-law, is a companded 8-bit audio encoding used mainly by North American and Japanese telephone systems, VoIP equipment, PBX software, and voice-mail systems. Files may use .ulaw, .ul, or a generic raw-audio extension.

Programs such as Asterisk, SIP recording systems, network telephony tools, and some digital telephone devices can create ULAW recordings. A raw ULAW file often contains only encoded samples, with no header describing the sample rate, channel count, or duration; telephone recordings are commonly 8,000 Hz, mono.

What the WAV format is

WAV is a RIFF-based audio container that stores audio data together with metadata such as sample rate, channels, bit depth, and codec. It is supported by most operating systems, audio editors, media players, and transcription applications.

WAV can contain μ-law audio, but PCM WAV is usually more compatible with editing software. Converting ULAW to PCM WAV decodes the 8-bit companded samples into linear PCM, normally 16-bit PCM, and does not restore detail that was absent from the telephone recording.

How to actually convert ULAW to WAV

For a raw 8,000 Hz mono file, FFmpeg provides a reliable desktop conversion:

ffmpeg -f mulaw -ar 8000 -ac 1 -i input.ulaw output.wav

-f mulaw identifies the raw μ-law encoding, -ar 8000 supplies the sample rate, and -ac 1 supplies the mono channel count. FFmpeg normally writes a widely compatible PCM WAV output. Replace those values if the recording system used different parameters.

To keep μ-law encoding inside a WAV container instead of decoding to PCM, use:

ffmpeg -f mulaw -ar 8000 -ac 1 -i input.ulaw -c:a pcm_mulaw output.wav

Use the first command for waveform editing and broad application compatibility. Use the second when preserving the original G.711 μ-law encoding matters and the target application supports μ-law WAV files.

You can also convert the file on 101convert.com for free without installing software. If the converter asks for audio properties, select μ-law encoding and enter the source sample rate and channel count; incorrect settings produce wrong speed, pitch, or channel interpretation.

Quality and compatibility limitations

ULAW is lossy 8-bit telephony audio, typically limited to a narrow voice bandwidth. Saving it as 16-bit PCM WAV increases file size and compatibility but does not improve recording quality.

Raw ULAW has no reliable way to identify its sample rate or channel layout. Obtain these values from the recording system or its documentation before converting; assuming 8,000 Hz mono is appropriate only for standard telephone audio.