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Voice Quality vs Sample Rate

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

IC Encoding Algorithm Sample Rate
(KHz)
4bit (ADPCM) 5bit (u-Law) 8bit (PCM) 16bit (PCM16)
aP89xxx V - V - 6K ~ 22K
aIVRxxxx V V V - 6K ~ 20K
aP23xxx V - V V 6K ~ 44K
aMTPxxx - - V V 6K ~ 44K

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 64sec , use 341sec ic body
  • Sample Rate = 8M / ( 64sec X 4bit ) ≒ 32KHz (4bit ADPCM)
  • Sample Rate = 8M / ( 64sec X 5bit ) ≒ 25.6KHz (5bit u-Law)
  • Sample Rate = 8M / ( 64sec X 8bit ) ≒ 16KHz (8bit PCM)
  • Sample Rate = 8M / ( 64sec X 16bit ) ≒ 8KHz (16bit PCM)

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

Encoding
Algorithm

Memory
Size

12KHz
4bit (ADPCM) 5bit (u-Law) 8bit (PCM) SBC 16bit (PCM16)
5sec 4sec 2.5sec - -
10sec 8.5sec 5sec - -
20sec 16.5sec 10sec - -
41sec 33sec 21sec - 10.5
85sec - 42sec - 21sec
170sec 133sec 85sec - 42sec
341sec - 170sec - 85sec
- - 333sec - -
- - - 4474sec 341sec

Note: Sound quality 16bit > SBC > 8bit > 5bit > 4bit

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