Neu ban da tung thay cac tuy chon nhu dBA, dBC hoac dBZ trong ung dung do am thanh, ban da gap trong so tan so. Cac chu cai sau dB thay doi co ban y nghia phep do cua ban va lieu du lieu cua ban co duoc co quan chap nhan hay khong.
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Trong so tan so la gi
Am thanh bao gom cac rung dong o nhieu tan so khac nhau. Tai nguoi khong nghe tat ca tan so nhu nhau: chung ta nhay cam nhat voi tan so tu 1000 Hz den 5000 Hz (dai giong noi) va it nhay cam hon nhieu voi tan so rat thap hoac rat cao. Mot am 50 Hz o 60 dB nghe nhe hon nhieu so voi am 2000 Hz o 60 dB, mac du ca hai co cung nang luong am.
Trong so tan so la mot bo loc toan hoc ap dung cho phep do de tinh den nhan thuc khong deu nay. Cac duong cong trong so khac nhau nhan manh hoac giam cac dai tan so cu the.
A-Weighting (dBA)
A-weighting la trong so tan so duoc su dung rong rai nhat trong do luong am thanh. No duoc thiet ke de xap xi dap ung tan so cua tai nguoi o muc vua phai. Duong cong A giam dang ke dong gop cua tan so thap: o 50 Hz ap dung khoang -30 dB suy giam. O 1000 Hz khong ap dung hieu chinh nao.
Khi nao su dung A-weighting
- Tuan thu tieng on noi lam viec. OSHA va NIOSH dat gioi han dua tren phep do trong so A.
- Giam sat moi truong. Quy dinh tieng on thanh pho chi dinh A-weighting.
- Khieu nai tieng on. Co quan mong doi phep do bang dBA.
- Tieng on giao thong. Nghien cuu tieng on duong bo va hang khong su dung A-weighting.
- Khi khong chac chan. A-weighting la lua chon mac dinh an toan nhat.
NoiseLedger ho tro A-weighting lam che do do mac dinh.
C-Weighting (dBC)
C-weighting cung cap dap ung tan so phang hon nhieu so voi A, dac biet trong dai tan so thap. Chi ap dung khoang -3 dB o 31,5 Hz va co ban phang tu 50 Hz den 8000 Hz. So doc dBC luon bang hoac cao hon dBA cho cung nguon. Chenh lech C-A lon hon 10 dB cho thay noi dung tan so thap dang ke.
Khi nao su dung C-weighting
- Tieng on dinh va xung. Nhieu quy dinh chi dinh dBC cho muc dinh (gioi han OSHA 140 dBC).
- Danh gia tan so thap. Khieu nai ve bass tu club, he thong HVAC hoac may cong nghiep.
- Dia diem am nhac. Muc concert thuong su dung C-weighting.
- Lua chon bao ve thinh giac. Chenh lech C-A giup xac dinh loai bao ve can thiet.
Z-Weighting (dBZ)
Z co nghia la “zero weighting”: khong ap dung bo loc tan so nao. Phep do phang (±1,5 dB) tu 10 Hz den 20.000 Hz, bat tat ca nang luong am deu nhau. Duoc chuan hoa trong IEC 61672:2003 de thay the cac ten goi “Linear” hoac “Flat” cu.
Khi nao su dung Z-weighting
- Nghien cuu am hoc. Khi can muc ap suat am thuc te khong co thien vi nhan thuc.
- Kiem tra thiet bi. Kiem tra loa va micro can phep do phang.
- Am hoc toa nha. Do cach am can du lieu khong trong so.
- Dac tinh nguon. Hieu noi dung tan so day du truoc khi chon trong so quy dinh.
NoiseLedger ho tro Z-weighting cung voi A-weighting, cho phep ban bat du lieu am khong loc de phan tich ky thuat.
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Bang so sanh nhanh
| Thong so | A (dBA) | C (dBC) | Z (dBZ) |
|---|---|---|---|
| Dap ung tan so | Loc tan so thap | Gan phang | Hoan toan phang |
| Mo phong | Thinh giac nguoi o muc vua | Thinh giac o muc cao | Khong mo phong nhan thuc |
| Tot nhat cho | Khieu nai, OSHA, giam sat chung | Tieng on dinh, tan so thap | Nghien cuu, hieu chuan |
| Do nhay tan so thap | Thap | Cao | Toan bo |
Nen su dung trong so nao
Dung A (dBA): do cho OSHA/NIOSH, ghi nhan khieu nai tieng on, khao sat moi truong, hoac khi khong chac chan. Dung C (dBC): do tieng on dinh hoac xung, nguon co noi dung tan so thap manh, quy dinh dia phuong yeu cau. Dung Z (dBZ): nghien cuu am hoc, kiem tra thiet bi audio, can du lieu khong loc, phan tich am hoc toa nha.
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Cau hoi thuong gap
Trong so tan so pho bien nhat la gi?
A-weighting (dBA) duoc su dung rong rai nhat tren the gioi. Duoc chi dinh boi OSHA, NIOSH, EPA va hau het cac quy dinh tieng on thanh pho.
Toi co the chuyen doi giua cac trong so trong NoiseLedger khong?
Co. NoiseLedger ho tro A va Z weighting, va ban co the chuyen doi trong cai dat ung dung. Hien thi pho FFT cung cap thong tin tan so chi tiet bat ke trong so duoc chon.
Trong so tan so co anh huong den so doc dB khong?
Co, dang ke. Cung nguon am se tao ra cac so doc khac nhau tuy thuoc vao trong so duoc chon. Doi voi tieng on co noi dung tan so thap manh, A-weighting se hien thi so doc thap hon dang ke so voi Z. Am 80 dBZ co the chi doc 65 dBA neu chu yeu la tan so thap.