{"id":5717,"date":"2025-06-28T16:44:17","date_gmt":"2025-06-28T09:44:17","guid":{"rendered":"https:\/\/spon.com.vn\/?p=5717"},"modified":"2025-06-28T16:50:05","modified_gmt":"2025-06-28T09:50:05","slug":"giai-thich-ve-muc-ap-suat-am-thanh-spl-y-nghia-do-luong-ung-dung-am-thanh","status":"publish","type":"post","link":"https:\/\/spon.com.vn\/?p=5717","title":{"rendered":"Gi\u1ea3i th\u00edch v\u1ec1 M\u1ee9c \u00e1p su\u1ea5t \u00e2m thanh (SPL): \u00dd ngh\u0129a, \u0110o l\u01b0\u1eddng & \u1ee8ng d\u1ee5ng \u00e2m thanh"},"content":{"rendered":"
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\u00c2m thanh l\u00e0 m\u1ed9t ph\u1ea7n c\u1ee7a cu\u1ed9c s\u1ed1ng h\u1eb1ng ng\u00e0y.<\/strong>
Ch\u00fang ta nghe th\u1ea5y \u00e2m thanh trong c\u00e1c cu\u1ed9c tr\u00f2 chuy\u1ec7n, \u00e2m nh\u1ea1c, c\u00e1c th\u00f4ng b\u00e1o c\u00f4ng c\u1ed9ng, v\u00e0 th\u1eadm ch\u00ed l\u00e0 ti\u1ebfng \u1ed3n n\u1ec1n tr\u00ean \u0111\u01b0\u1eddng ph\u1ed1 \u0111\u00f4ng \u0111\u00fac. Nh\u01b0ng b\u1ea1n \u0111\u00e3 bao gi\u1edd t\u1ef1 h\u1ecfi l\u00e0m sao \u0111\u1ec3 \u0111o \u0111\u01b0\u1ee3c \u0111\u1ed9 to c\u1ee7a \u00e2m thanh ch\u01b0a? \u0110\u00f3 l\u00e0 l\u00fac M\u1ee9c \u00c1p Su\u1ea5t \u00c2m thanh (Sound Pressure Level – SPL)<\/strong> xu\u1ea5t hi\u1ec7n. SPL l\u00e0 m\u1ed9t c\u00e1ch khoa h\u1ecdc \u0111\u1ec3 m\u00f4 t\u1ea3 \u0111\u1ed9 m\u1ea1nh c\u1ee7a \u00e2m thanh, s\u1eed d\u1ee5ng \u0111\u01a1n v\u1ecb g\u1ecdi l\u00e0 decibel (dB)<\/strong>. B\u00e0i vi\u1ebft n\u00e0y s\u1ebd gi\u1ea3i th\u00edch SPL l\u00e0 g\u00ec, c\u00e1ch \u0111o SPL, t\u1ea7m quan tr\u1ecdng c\u1ee7a n\u00f3, v\u00e0 SPL \u1ea3nh h\u01b0\u1edfng nh\u01b0 th\u1ebf n\u00e0o \u0111\u1ebfn c\u00e1c l\u0129nh v\u1ef1c nh\u01b0 thi\u1ebft k\u1ebf loa v\u00e0 an to\u00e0n th\u00ednh l\u1ef1c.<\/p>\n

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SPL ngh\u0129a l\u00e0 g\u00ec?<\/strong><\/p>\n

\u0110\u1ea1i l\u01b0\u1ee3ng v\u1eadt l\u00fd ph\u1ed5 bi\u1ebfn nh\u1ea5t d\u00f9ng \u0111\u1ec3 \u0111o \u00e2m thanh l\u00e0 \u00e1p su\u1ea5t \u00e2m thanh (sound pressure)<\/strong>. M\u1ee9c \u0111\u1ed9 c\u1ee7a \u00e1p su\u1ea5t \u00e2m thanh th\u01b0\u1eddng \u0111\u01b0\u1ee3c m\u00f4 t\u1ea3 b\u1eb1ng M\u1ee9c \u00c1p Su\u1ea5t \u00c2m thanh (SPL)<\/strong>. N\u00f3 cho ch\u00fang ta bi\u1ebft s\u00f3ng \u00e2m m\u1ea1nh \u0111\u1ebfn m\u1ee9c n\u00e0o \u2014 hay \u0111\u01a1n gi\u1ea3n h\u01a1n, \u00e2m thanh \u0111\u00f3 to \u0111\u1ebfn \u0111\u00e2u \u0111\u1ed1i v\u1edbi tai ng\u01b0\u1eddi.<\/p>\n

SPL \u0111\u01b0\u1ee3c t\u00ednh b\u1eb1ng c\u00e1ch l\u1ea5y t\u1ef7 s\u1ed1 gi\u1eefa \u00e1p su\u1ea5t \u00e2m hi\u1ec7u d\u1ee5ng so v\u1edbi \u00e1p su\u1ea5t \u00e2m tham chi\u1ebfu (2\u00d710\u207b\u2075 Pa), s\u1eed d\u1ee5ng logarit c\u01a1 s\u1ed1 10, sau \u0111\u00f3 nh\u00e2n v\u1edbi 20. \u0110\u01a1n v\u1ecb l\u00e0 decibel (dB). D\u1ea3i \u00e1p su\u1ea5t \u00e2m m\u00e0 tai ng\u01b0\u1eddi c\u00f3 th\u1ec3 nghe \u0111\u01b0\u1ee3c l\u00e0 t\u1eeb 2\u00d710\u207b\u2075 Pa \u0111\u1ebfn 20 Pa<\/strong>, t\u01b0\u01a1ng \u0111\u01b0\u01a1ng v\u1edbi 0 \u0111\u1ebfn 120 dB SPL<\/strong>.<\/p>\n

Tuy nhi\u00ean, ph\u00e9p t\u00ednh decibel c\u00f3 th\u1ec3 g\u00e2y nh\u1ea7m l\u1eabn, v\u00ec ch\u1ec9 m\u1ed9t s\u1ef1 gia t\u0103ng nh\u1ecf trong dB<\/strong> c\u0169ng c\u00f3 th\u1ec3 \u0111\u1ed3ng ngh\u0129a v\u1edbi s\u1ef1 t\u0103ng r\u1ea5t l\u1edbn v\u1ec1 \u0111\u1ed9 to<\/strong>. V\u00ed d\u1ee5, \u00e2m thanh 60 dB kh\u00f4ng ch\u1ec9 to g\u1ea5p \u0111\u00f4i 30 dB \u2014 m\u00e0 n\u00f3 to h\u01a1n r\u1ea5t nhi\u1ec1u<\/strong>.<\/p>\n

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\u00a0<\/p>\n

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T\u1ea1i sao SPL l\u1ea1i quan tr\u1ecdng?<\/strong><\/h3>\n

SPL l\u00e0 gi\u00e1 tr\u1ecb quan tr\u1ecdng \u0111\u1ec3 \u0111o \u0111\u1ed9 to c\u1ee7a \u00e2m thanh<\/strong>. N\u00f3 \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng trong gi\u00e1m s\u00e1t ti\u1ebfng \u1ed3n m\u00f4i tr\u01b0\u1eddng<\/strong>, k\u1ef9 thu\u1eadt \u00e2m thanh<\/strong>, v\u00e0 ki\u1ec3m tra s\u1ea3n ph\u1ea9m<\/strong>. Trong ng\u00e0nh c\u00f4ng nghi\u1ec7p \u00e2m thanh, c\u00e1c nh\u00e0 thi\u1ebft k\u1ebf loa s\u1eed d\u1ee5ng SPL \u0111\u1ec3 \u0111o \u0111\u1ed9 to c\u1ee7a s\u1ea3n ph\u1ea9m. SPL c\u00e0ng cao ngh\u0129a l\u00e0 loa ph\u00e1t ra \u00e2m thanh to h\u01a1n v\u1edbi c\u00f4ng su\u1ea5t ti\u00eau th\u1ee5 \u00edt h\u01a1n.<\/strong><\/p>\n

T\u1ea1i c\u00e1c tr\u01b0\u1eddng h\u1ecdc<\/strong> v\u00e0 v\u0103n ph\u00f2ng<\/strong>, SPL gi\u00fap thi\u1ebft k\u1ebf h\u1ec7 th\u1ed1ng \u00e2m thanh sao cho th\u00f4ng b\u00e1o v\u1eabn \u0111\u01b0\u1ee3c nghe r\u00f5 r\u00e0ng<\/strong>, ngay c\u1ea3 trong m\u00f4i tr\u01b0\u1eddng c\u00f3 nhi\u1ec1u ti\u1ebfng \u1ed3n. Trong an to\u00e0n lao \u0111\u1ed9ng v\u00e0 c\u00f4ng nghi\u1ec7p<\/strong>, ti\u1ebfng \u1ed3n qu\u00e1 l\u1edbn (SPL cao)<\/strong> c\u00f3 th\u1ec3 g\u00e2y t\u1ed5n th\u01b0\u01a1ng th\u00ednh gi\u00e1c<\/strong>. M\u00e1y \u0111o SPL \u0111\u01b0\u1ee3c d\u00f9ng \u0111\u1ec3 ki\u1ec3m tra m\u1ee9c \u0111\u1ed9 an to\u00e0n ti\u1ebfng \u1ed3n trong m\u00f4i tr\u01b0\u1eddng l\u00e0m vi\u1ec7c<\/strong>.<\/p>\n

V\u1edbi ng\u01b0\u1eddi d\u00f9ng c\u00e1 nh\u00e2n<\/strong>, hi\u1ec3u r\u00f5 m\u1ee9c SPL an to\u00e0n<\/strong> gi\u00fap tr\u00e1nh m\u1ea5t th\u00ednh l\u1ef1c<\/strong> do nghe nh\u1ea1c qu\u00e1 l\u1edbn ho\u1eb7c d\u00f9ng tai nghe kh\u00f4ng \u0111\u00fang c\u00e1ch.<\/p>\n

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SPL \u0111\u01b0\u1ee3c \u0111o nh\u01b0 th\u1ebf n\u00e0o?<\/strong><\/h3>\n

SPL th\u01b0\u1eddng \u0111\u01b0\u1ee3c \u0111o b\u1eb1ng m\u1ed9t thi\u1ebft b\u1ecb chuy\u00ean d\u1ee5ng g\u1ecdi l\u00e0 m\u00e1y \u0111o m\u1ee9c \u00e2m thanh (Sound Level Meter – SLM)<\/strong>. Thi\u1ebft b\u1ecb n\u00e0y ph\u00e1t hi\u1ec7n c\u00e1c thay \u0111\u1ed5i \u00e1p su\u1ea5t kh\u00f4ng kh\u00ed do \u00e2m thanh g\u00e2y ra v\u00e0 hi\u1ec3n th\u1ecb k\u1ebft qu\u1ea3 b\u1eb1ng \u0111\u01a1n v\u1ecb decibel (dB SPL)<\/strong>.<\/p>\n

Trong th\u1ef1c t\u1ebf, \u00e2m thanh thay \u0111\u1ed5i r\u1ea5t nhanh, v\u00ec v\u1eady c\u00e1c c\u00e0i \u0111\u1eb7t tr\u1ecdng s\u1ed1 th\u1eddi gian (Time Weighting)<\/strong> r\u1ea5t quan tr\u1ecdng. T\u00f9y tr\u01b0\u1eddng h\u1ee3p m\u00e0 ch\u1ecdn ch\u1ebf \u0111\u1ed9 ph\u00f9 h\u1ee3p \u0111\u1ec3 ph\u1ea3n \u00e1nh s\u1ef1 thay \u0111\u1ed5i \u00e2m thanh theo th\u1eddi gian:<\/p>\n

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    Tr\u1ecdng s\u1ed1 ch\u1eadm (Slow weighting)<\/strong>: D\u00f9ng trong nh\u00e0 m\u00e1y, n\u01a1i l\u00e0m vi\u1ec7c. N\u00f3 ph\u1ea3n \u00e1nh m\u1ee9c \u00e2m trung b\u00ecnh \u1ed5n \u0111\u1ecbnh, gi\u1ed1ng nh\u01b0 tai ng\u01b0\u1eddi ph\u1ea3n \u1ee9ng v\u1edbi ti\u1ebfng \u1ed3n li\u00ean t\u1ee5c.<\/p>\n<\/li>\n

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    Tr\u1ecdng s\u1ed1 nhanh (Fast weighting)<\/strong>: D\u00f9ng \u0111\u1ec3 gi\u00e1m s\u00e1t ti\u1ebfng \u1ed3n th\u00f4ng th\u01b0\u1eddng. N\u00f3 ph\u1ea3n \u1ee9ng nhanh, hi\u1ec3n th\u1ecb c\u00e1c thay \u0111\u1ed5i ng\u1eafn trong \u00e2m thanh.<\/p>\n<\/li>\n

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    Tr\u1ecdng s\u1ed1 xung (Impulse weighting)<\/strong>: D\u00f9ng \u0111\u1ec3 ph\u00e1t hi\u1ec7n \u00e2m thanh \u0111\u1ed9t ng\u1ed9t<\/strong> nh\u01b0 m\u00e1y m\u00f3c va ch\u1ea1m, n\u1ed5, ho\u1eb7c ti\u1ebfng s\u00fang. N\u00f3 th\u1ec3 hi\u1ec7n c\u00e1c \u0111\u1ec9nh \u00e2m m\u1ea1nh r\u00f5 r\u00e0ng h\u01a1n.<\/p>\n<\/li>\n<\/ol>\n

    Ngo\u00e0i tr\u1ecdng s\u1ed1 th\u1eddi gian, c\u00f2n c\u00f3 tr\u1ecdng s\u1ed1 t\u1ea7n s\u1ed1 (Frequency Weighting)<\/strong> \u0111\u1ec3 m\u00f4 ph\u1ecfng c\u00e1ch con ng\u01b0\u1eddi c\u1ea3m nh\u1eadn \u00e2m thanh \u1edf c\u00e1c t\u1ea7n s\u1ed1 kh\u00e1c nhau. C\u00e1c lo\u1ea1i ph\u1ed5 bi\u1ebfn g\u1ed3m:<\/p>\n

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      A-weighting<\/strong>: C\u00e0i \u0111\u1eb7t ph\u1ed5 bi\u1ebfn nh\u1ea5t. Gi\u1ea3m t\u1ea7n s\u1ed1 th\u1ea5p v\u00e0 cao, t\u1eadp trung v\u00e0o d\u1ea3i t\u1ea7n trung (kho\u1ea3ng 500 Hz \u2013 10 kHz) \u2014 d\u1ea3i m\u00e0 tai ng\u01b0\u1eddi nh\u1ea1y c\u1ea3m nh\u1ea5t. D\u00f9ng trong \u0111o ti\u1ebfng \u1ed3n m\u00f4i tr\u01b0\u1eddng v\u00e0 n\u01a1i l\u00e0m vi\u1ec7c.<\/p>\n<\/li>\n

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      C-weighting<\/strong>: G\u1ea7n nh\u01b0 ph\u1eb3ng, gi\u1eef h\u1ea7u h\u1ebft c\u00e1c t\u1ea7n s\u1ed1, ch\u1ec9 gi\u1ea3m nh\u1eb9 \u00e2m r\u1ea5t th\u1ea5p v\u00e0 r\u1ea5t cao. D\u00f9ng trong \u0111o ti\u1ebfng \u1ed3n l\u1edbn nh\u01b0 \u1edf concert, c\u00f4ng tr\u01b0\u1eddng, s\u00e2n bay.<\/p>\n<\/li>\n

    3. \n

      Z-weighting<\/strong> (c\u00f2n g\u1ecdi l\u00e0 “linear” hay “zero weighting”): Kh\u00f4ng thay \u0111\u1ed5i b\u1ea5t k\u1ef3 t\u1ea7n s\u1ed1 n\u00e0o, t\u1ea5t c\u1ea3 \u0111\u01b0\u1ee3c \u0111\u1ed1i x\u1eed nh\u01b0 nhau. D\u00f9ng trong ki\u1ec3m tra khoa h\u1ecdc ho\u1eb7c hi\u1ec7u chu\u1ea9n thi\u1ebft b\u1ecb<\/strong>.<\/p>\n<\/li>\n<\/ol>\n

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      \u0110\u1ec3 \u0111o SPL ch\u00ednh x\u00e1c, c\u1ea7n \u0111\u1eb7t m\u00e1y \u0111o c\u00e1ch ngu\u1ed3n \u00e2m 1 m\u00e9t<\/strong>, v\u00e0 ngang t\u1ea7m tai ng\u01b0\u1eddi nghe<\/strong>. Micro t\u00edch h\u1ee3p trong m\u00e1y s\u1ebd nh\u1eadn \u00e2m thanh v\u00e0 chuy\u1ec3n th\u00e0nh m\u1ee9c \u00e1p su\u1ea5t \u00e2m thanh, hi\u1ec3n th\u1ecb d\u01b0\u1edbi d\u1ea1ng dB SPL<\/strong> tr\u00ean m\u00e0n h\u00ecnh.<\/p>\n

      Trong ki\u1ec3m tra loa<\/strong>, quy t\u1eafc ph\u1ed5 bi\u1ebfn l\u00e0 \u0111o theo \u0111i\u1ec1u ki\u1ec7n \u201c1W\/1m<\/strong>\u201d \u2014 t\u1ee9c l\u00e0 d\u00f9ng 1 watt c\u00f4ng su\u1ea5t<\/strong> \u0111\u1ea7u v\u00e0o v\u00e0 \u0111o t\u1eeb kho\u1ea3ng c\u00e1ch 1 m\u00e9t<\/strong>. \u0110i\u1ec1u n\u00e0y gi\u00fap \u0111\u00e1nh gi\u00e1 hi\u1ec7u su\u1ea5t (\u0111\u1ed9 nh\u1ea1y)<\/strong> c\u1ee7a loa v\u00e0 d\u1ec5 d\u00e0ng so s\u00e1nh gi\u1eefa c\u00e1c m\u1eabu loa kh\u00e1c nhau.<\/strong><\/p>\n<\/div>\n<\/div>\n<\/div>\n

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      \u00a0<\/p>\n

      \"Sound<\/p>\n

      \u00a0<\/p>\n

      Ng\u00e0y nay, nhi\u1ec1u \u1ee9ng d\u1ee5ng tr\u00ean \u0111i\u1ec7n tho\u1ea1i th\u00f4ng minh c\u0169ng c\u00f3 th\u1ec3 \u0111o SPL.<\/strong>
      M\u1eb7c d\u00f9 micro v\u00e0 t\u1ed1c \u0111\u1ed9 l\u1ea5y m\u1eabu<\/strong> c\u1ee7a \u0111i\u1ec7n tho\u1ea1i kh\u00f4ng ch\u00ednh x\u00e1c nh\u01b0 c\u00e1c thi\u1ebft b\u1ecb \u0111o chuy\u00ean nghi\u1ec7p<\/strong>, nh\u01b0ng ch\u00fang v\u1eabn c\u00f3 th\u1ec3 cung c\u1ea5p \u01b0\u1edbc l\u01b0\u1ee3ng s\u01a1 b\u1ed9<\/strong> v\u1ec1 m\u1ee9c \u0111\u1ed9 ti\u1ebfng \u1ed3n trong c\u00e1c t\u00ecnh hu\u1ed1ng kh\u00f4ng chuy\u00ean nghi\u1ec7p<\/strong>.<\/p>\n

      H\u00e3y c\u00f9ng xem m\u1ed9t bi\u1ec3u \u0111\u1ed3 \u0111\u01a1n gi\u1ea3n.
      \u0110\u01b0\u1eddng m\u00e0u xanh<\/strong> bi\u1ec3u th\u1ecb m\u1ee9c \u00e1p su\u1ea5t \u00e2m t\u1ee9c th\u1eddi<\/strong>, t\u1ee9c l\u00e0 m\u1ee9c \u00e1p su\u1ea5t m\u00e0 micro thu nh\u1eadn \u0111\u01b0\u1ee3c theo th\u1eddi gian th\u1ef1c<\/strong>.
      Gi\u00e1 tr\u1ecb n\u00e0y thay \u0111\u1ed5i r\u1ea5t nhanh<\/strong> v\u00e0 th\u01b0\u1eddng dao \u0111\u1ed9ng m\u1ea1nh<\/strong>. V\u00ec l\u00fd do \u0111\u00f3, vi\u1ec7c hi\u1ec3u r\u00f5 m\u1ee9c \u0111\u1ed9 \u00e2m thanh<\/strong> ch\u1ec9 b\u1eb1ng c\u00e1ch quan s\u00e1t c\u00e1c gi\u00e1 tr\u1ecb t\u1ee9c th\u1eddi s\u1ebd r\u1ea5t kh\u00f3 kh\u0103n.<\/strong><\/p>\n

      \u00a0<\/p>\n

      \"measure<\/p>\n

      Trong nhi\u1ec1u tr\u01b0\u1eddng h\u1ee3p, ch\u00fang ta s\u1eed d\u1ee5ng gi\u00e1 tr\u1ecb g\u1ecdi l\u00e0 Leq<\/strong>, t\u1ee9c l\u00e0 m\u1ee9c SPL li\u00ean t\u1ee5c t\u01b0\u01a1ng \u0111\u01b0\u01a1ng<\/strong> trong su\u1ed1t th\u1eddi gian \u0111o.<\/h3>\n

      Gi\u00e1 tr\u1ecb n\u00e0y ph\u00f9 h\u1ee3p v\u1edbi c\u1ea3m nh\u1eadn th\u1ef1c t\u1ebf c\u1ee7a con ng\u01b0\u1eddi<\/strong> \u0111\u1ed1i v\u1edbi \u00e2m thanh.
      V\u00ed d\u1ee5: sau m\u1ed9t s\u1ef1 ki\u1ec7n, n\u1ebfu m\u1ecdi ng\u01b0\u1eddi n\u00f3i r\u1eb1ng \u00e2m thanh v\u1eeba ph\u1ea3i, d\u1ec5 ch\u1ecbu<\/strong>, th\u00ec \u0111\u01b0\u1eddng cong Leq th\u01b0\u1eddng m\u01b0\u1ee3t m\u00e0<\/strong>. Nh\u01b0ng n\u1ebfu gi\u00e1 tr\u1ecb Leq r\u1ea5t cao<\/strong>, \u0111i\u1ec1u \u0111\u00f3 c\u00f3 ngh\u0129a l\u00e0 s\u1ef1 ki\u1ec7n \u0111\u00f3 r\u1ea5t \u1ed3n<\/strong>.
      Do Leq ph\u1ea3n \u00e1nh r\u1ea5t s\u00e1t c\u1ea3m nh\u1eadn c\u1ee7a tai ng\u01b0\u1eddi<\/strong>, n\u00f3 l\u00e0 m\u1ed9t trong nh\u1eefng gi\u00e1 tr\u1ecb quan tr\u1ecdng nh\u1ea5t<\/strong> trong vi\u1ec7c ki\u1ec3m tra v\u00e0 \u0111\u00e1nh gi\u00e1 \u00e2m thanh.<\/p>\n

      \n

      C\u00e1ch t\u00ednh SPL<\/strong><\/h3>\n

      \u0110\u1ec3 t\u00ednh SPL ch\u00ednh x\u00e1c, ch\u00fang ta ph\u1ea3i s\u1eed d\u1ee5ng gi\u00e1 tr\u1ecb hi\u1ec7u d\u1ee5ng t\u1ed5ng th\u1ec3 tr\u00ean to\u00e0n d\u1ea3i t\u1ea7n s\u1ed1<\/strong>, ch\u1ee9 kh\u00f4ng ch\u1ec9 t\u1ea1i m\u1ed9t th\u1eddi \u0111i\u1ec3m.
      T\u00edn hi\u1ec7u ti\u1ebfng \u1ed3n \u0111\u01b0\u1ee3c c\u1ea3m bi\u1ebfn ghi l\u1ea1i l\u00e0 m\u1ed9t d\u1ea1ng s\u00f3ng theo th\u1eddi gian<\/strong> (time-domain waveform), ngh\u0129a l\u00e0 \u00e1p su\u1ea5t \u00e2m<\/a> thay \u0111\u1ed5i li\u00ean t\u1ee5c theo th\u1eddi gian<\/strong>, c\u00f3 c\u1ea3 gi\u00e1 tr\u1ecb \u00e2m v\u00e0 d\u01b0\u01a1ng<\/strong>.<\/p>\n

      Tuy nhi\u00ean, trong to\u00e1n h\u1ecdc, logarit (\u0111\u01b0\u1ee3c d\u00f9ng trong t\u00ednh SPL)<\/strong> ch\u1ec9 c\u00f3 th\u1ec3 t\u00ednh v\u1edbi gi\u00e1 tr\u1ecb d\u01b0\u01a1ng<\/strong>. V\u00ec th\u1ebf, ch\u00fang ta kh\u00f4ng th\u1ec3 d\u00f9ng tr\u1ef1c ti\u1ebfp c\u00e1c gi\u00e1 tr\u1ecb t\u1ee9c th\u1eddi<\/strong> c\u1ee7a \u00e1p su\u1ea5t \u00e2m.
      Thay v\u00e0o \u0111\u00f3, ta d\u00f9ng gi\u00e1 tr\u1ecb trung b\u00ecnh b\u00ecnh ph\u01b0\u01a1ng (RMS – Root Mean Square)<\/strong>, lu\u00f4n l\u00e0 s\u1ed1 d\u01b0\u01a1ng v\u00e0 \u0111\u1ea1i di\u1ec7n cho n\u0103ng l\u01b0\u1ee3ng t\u1ed5ng th\u1ec3 c\u1ee7a \u00e2m thanh<\/strong>.
      \u0110\u00f3 l\u00e0 l\u00fd do t\u1ea5t c\u1ea3 c\u00e1c ph\u00e9p t\u00ednh SPL \u0111\u1ec1u d\u1ef1a tr\u00ean gi\u00e1 tr\u1ecb RMS tr\u00ean to\u00e0n d\u1ea3i t\u1ea7n<\/strong>, c\u00f2n g\u1ecdi l\u00e0 m\u1ee9c t\u1ed5ng th\u1ec3 (Overall Level)<\/strong>.<\/p>\n

      \n

      A, B, C v\u00e0 Z – C\u00e1c d\u1ea1ng tr\u1ecdng s\u1ed1 t\u1ea7n s\u1ed1 l\u00e0 g\u00ec?<\/strong><\/h3>\n

      T\u1ea7n s\u1ed1 \u00e2m thanh \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn c\u00e1ch \u0111o SPL<\/strong>, v\u00ec tai ng\u01b0\u1eddi kh\u00f4ng c\u1ea3m nh\u1eadn t\u1ea5t c\u1ea3 t\u1ea7n s\u1ed1 nh\u01b0 nhau<\/strong>.
      \u0110\u1ec3 \u0111i\u1ec1u ch\u1ec9nh \u0111i\u1ec1u n\u00e0y, m\u00e1y \u0111o m\u1ee9c \u00e2m thanh s\u1eed d\u1ee5ng c\u00e1c b\u1ed9 l\u1ecdc tr\u1ecdng s\u1ed1 t\u1ea7n s\u1ed1<\/strong> (frequency weighting) \u0111\u1ec3 m\u00f4 ph\u1ecfng c\u00e1ch tai ng\u01b0\u1eddi ph\u1ea3n \u1ee9ng v\u1edbi t\u1eebng t\u1ea7n s\u1ed1 kh\u00e1c nhau.
      C\u00e1c lo\u1ea1i ph\u1ed5 bi\u1ebfn nh\u1ea5t l\u00e0: A, C v\u00e0 Z<\/strong>, v\u00e0 c\u00f3 th\u00eam lo\u1ea1i \u00edt d\u00f9ng l\u00e0 B<\/strong>.<\/p>\n

      \n

      A-weighting<\/strong><\/h3>\n