Au file format - Wikipedia

A simple audio file format that consists of a header of 6 32-bit words and then the data. The format was introduced by Sun Microsystems.

32 bit word field description/ content

0 magic number the value 0x2e736e64 (four ASCII characters ".snd")

1 data offset the offset to the data in bytes. The minimum valid number is 24 (decimal).

2 data size data size in bytes. If unknown, the value 0xffffffff should be used.

3 encoding Data encoding format: 1=8-bit ISDN u-law, 2=8-bit linear PCM [REF-PCM], 3=16-bit linear PCM, 4=24-bit linear PCM, 5=32-bit linear PCM, 6=32-bit IEEE floating point, 7=64-bit IEEE floating point, 23=8-bit ISDN u-law compressed using the UIT-T G.721 ADPCM voice data encoding scheme.

4 sample rate the number of samples/second (e.g., 8000)

5 channels the number of interleaved channels (e.g., 1 for mono, 2 for stereo)

32 bit word	field	description/ content
0	magic number	the value 0x2e736e64 (four ASCII characters ".snd")
1	data offset	the offset to the data in bytes. The minimum valid number is 24 (decimal).
2	data size	data size in bytes. If unknown, the value 0xffffffff should be used.
3	encoding	Data encoding format: 1=8-bit ISDN u-law, 2=8-bit linear PCM [REF-PCM], 3=16-bit linear PCM, 4=24-bit linear PCM, 5=32-bit linear PCM, 6=32-bit IEEE floating point, 7=64-bit IEEE floating point, 23=8-bit ISDN u-law compressed using the UIT-T G.721 ADPCM voice data encoding scheme.
4	sample rate	the number of samples/second (e.g., 8000)
5	channels	the number of interleaved channels (e.g., 1 for mono, 2 for stereo)