качество голоса и частота

APLUS VOICE IC allow user define different sample rate and encoding algorithm to get the best sound quality.

IC Encoding AlgorithmSample Rate
(KHz)
4bit (ADPCM) 5bit (u-Law) 8bit (PCM)
  • aP89xxx
V - V 6K ~ 22K
  • aIVRxxxx
V V V 6K ~ 20K
  • aMTPxxx
- - V 6K ~ 20K

Let's listen the sound quality base on 6KHz, 12KHz and 18KHz/8bit.

Sound quality︰

Obviously 18K Hz > 12K Hz > 6K Hz sound quality. Higher sample rate will have better sound quality. Generally speaking, suggest higher than 12KHz.

How to calculate sample rate ?

Maximum Sample Rate = Memory Size / (voice duration x Data encoding algoritm)

Ex Sound total 32sec , use aIVR8511 body
Sample Rate = 2M / ( 32sec X 4bit ) ≒ 15.6KHz (4bit ADPCM)
Sample Rate = 2M / ( 32sec X 5bit ) ≒ 12.5KHz (5bit u-Law)
Sample Rate = 2M / ( 32sec X 8bit ) ≒ 7.8KHz (8bit PCM)

Below table show how many seconds we can program for each body In 12KHz.

12KHz
4bit (ADPCM) 5bit (u-Law) 8bit (PCM)
5sec 4sec 2.5sec
10sec 8.5sec 5.5sec
20sec 16.5sec 10sec
41sec 33sec 20.5sec
83sec - 42.5sec
166sec 133sec 83sec
- - 333sec

Note: 8bit sound quality > 5bit sound quality > 4bit sound quality