How many sample size should we test at speech recognition test

I am looking for the information and knowledge that How many sample size should we test for the speech recognition

  1. Automatic test

    • if we test with audio file, we can test automatically, but we have test system and recorded audio file. Q) How many recorded audio file when we test? so when we test reliability sample number data, we can get reliability test result

      1. Manual test if we don't have automatic system, we can test manually. it tests people directly, when we test, we have many tester, but this method have to spend many time, money.

for these reason, we want to define sample size(number) for those test

thanks your response in advance