AAC is the abbreviation of Advanced Audio Coding. AAC was developed by the Moving Picture Experts Group (MPEG) and has been discussed and approved by the International Organization for Standardization (ISO), becoming a part of the MPEG-2 international standard, and it is also an open audio coding standard. 

1) AAC is an audio compression algorithm with a high compression ratio, but its compression ratio far exceeds the older audio compression algorithms, such as AC-3, MP3, etc. And its quality is comparable to that of uncompressed CD sound. 

2) Like other similar audio coding algorithms, AAC also uses transform coding algorithms, but AAC uses a higher resolution filter bank, so it can achieve a higher compression ratio. 

3) AAC uses the latest technologies such as temporary noise rearrangement, backward adaptive linear prediction, joint stereo technology and quantized Huffman coding. The use of these new technologies has further improved the compression ratio. 

4) AAC supports more sample rates and bit rates, supports 1 to 48 audio tracks, supports up to 15 low frequency audio tracks, has multi-language compatibility, and up to 15 embedded data streams. 

5) AAC supports a wider sound frequency range, the highest can reach 96kHz, the lowest can reach 8Hz, which is much wider than MP3's 20-44kHz range. Unlike MP3 and WMA, AAC hardly loses the very high and very low sound frequencies Frequency components, and are closer to the original audio frequency spectrum structure than WMA, so the sound fidelity is better. Professional evaluation shows that AAC has clearer sound than WMA and is closer to the original sound. 

6) The sampling rate of Haikang equipment is 16Khz, and the mAA code rate is 16-64KBPS can be set.