1. ㉠5dB이상 ㉡ [+10log(/20}]
2. ㉠10dB이상 ㉡ [+10log(/20}]
3. ㉠5dB이상 ㉡ [+20log(/20}]
4. ㉠10dB이상 ㉡ [+20log(/20}]