Ch\u00fang ta \u0111\u1ec1u bi\u1ebft \u00e2m thanh l\u00e0 do ch\u1ea5n \u0111\u1ed9ng sinh ra, \u00e2m thanh cao hay th\u1ea5p l\u00e0 do t\u1ea7n s\u1ed1 c\u1ee7a ch\u1ea5n \u0111\u1ed9ng quy\u1ebft \u0111\u1ecbnh. N\u00e9t \u0111\u1eb9p c\u1ee7a m\u1ed9t kh\u00fac nh\u1ea1c l\u00e0 \u201cgiai \u0111i\u1ec7u\u201d, l\u00e0 s\u1ef1 ph\u1ed1i h\u1ee3p l\u1eabn nhau gi\u1eefa nhi\u1ec1u \u00e2m thanh v\u1ec1 \u0111\u1ed9 d\u00e0i, c\u01b0\u1eddng \u0111\u1ed9 ho\u1eb7c ph\u00e1t ra \u0111\u1ed3ng th\u1eddi ho\u1eb7c theo th\u1ee9 t\u1ef1 tr\u01b0\u1edbc sau \u0111em l\u1ea1i. Giai \u0111i\u1ec7u l\u00e0 s\u1ef1 c\u1ea3m nh\u1eadn v\u1ec1 t\u00e2m l\u00ed, nh\u01b0ng ng\u01b0\u1eddi ta c\u0169ng nhanh ch\u00f3ng nh\u1eadn ra c\u01a1 s\u1edf v\u1eadt ch\u1ea5t th\u1ef1c s\u1ef1 c\u1ee7a giai \u0111i\u1ec7u. Ho\u1eb7c n\u1ebfu d\u00f9ng to\u00e1n h\u1ecdc \u0111\u1ec3 gi\u1ea3i th\u00edch: khi hai ho\u1eb7c nhi\u1ec1u \u00e2m thanh c\u00f3 t\u1ec9 s\u1ed1 c\u00e1c t\u1ea7n s\u1ed1 l\u00e0 t\u1ec9 s\u1ed1 c\u1ee7a hai s\u1ed1 nguy\u00ean t\u1ed1i gi\u1ea3n th\u00ec ch\u00fang l\u00e0 giai \u0111i\u1ec7u. T\u1ec9 s\u1ed1 t\u1ed1i gi\u1ea3n \u0111\u01b0\u01a1ng nhi\u00ean l\u00e0 1\/2. Trong \u00e2m nh\u1ea1c, n\u1ebfu t\u1ec9 s\u1ed1 t\u1ea7n s\u1ed1 hai \u00e2m thanh b\u1eb1ng 1\/2 th\u00ec \u00e2m thanh c\u00f3 t\u1ea7n s\u1ed1 cao l\u00e0 \u00e2m c\u00f3 c\u00f9ng t\u00ean v\u00e0 c\u00e1ch nhau m\u1ed9t b\u00e1t \u0111\u1ed9 hay c\u00f2n g\u1ecdi l\u00e0 qu\u00e3ng t\u00e1m. Nh\u01b0 \u00e2m (n\u1ed1t) \u0111\u00f4 v\u00e0 \u00e2m c\u00f3 t\u1ea7n s\u1ed1 cao g\u1ea5p \u0111\u00f4i l\u00e0 \u00e2m \u201c\u0111\u1ed1\u201d l\u00e0 hai \u00e2m c\u00f3 t\u00ean nh\u01b0 nhau nh\u01b0ng \u00e2m \u0111\u1ed1 c\u00f3 \u0111\u1ed9 cao cao h\u01a1n \u00e2m \u0111\u00f4 m\u1ed9t qu\u00e3ng t\u00e1m. X\u00e9t v\u1ec1 t\u00ednh \u0111\u01a1n gi\u1ea3n th\u00ec t\u1ec9 s\u1ed1 2\/3 \u0111\u1ee9ng sau t\u1ec9 s\u1ed1 1\/2. \u00c2m thanh c\u00f3 t\u1ea7n s\u1ed1 g\u1ea5p 3\/2 l\u1ea7n t\u1ea7n s\u1ed1 \u00e2m \u0111\u00f4 l\u00e0 \u00e2m sol\u2026Theo c\u00f9ng m\u1ed9t \u00fd t\u01b0\u1edfng \u0111\u00f3, lo\u00e0i ng\u01b0\u1eddi \u0111\u00e3 ph\u00e1t minh ra \u00e2m giai b\u1ea3y \u00e2m trong \u00e2m nh\u1ea1c g\u1ecdi l\u00e0 \u201c\u00e2m lu\u1eadt\u201d b\u1ea3y \u00e2m. Trong b\u1ea3ng d\u01b0\u1edbi \u0111\u00e2y s\u1ebd d\u1eabn ra t\u1ea7n s\u1ed1 \u00e2m giai b\u1ea3y \u00e2m trong \u201c\u00e2m lu\u1eadt\u201d b\u1ea3y \u00e2m (gi\u1ea3 thi\u1ebft t\u1ea7n s\u1ed1 \u00e2m \u0111\u00f4 l\u00e0 520 hec, c\u00e1c t\u1ea7n s\u1ed1 ch\u1ec9 ghi ph\u1ea7n ch\u1eb5n, b\u1ecf qua ph\u1ea7n l\u1ebb) c\u0169ng nh\u01b0 t\u1ec9 s\u1ed1 gi\u1eefa t\u1ea7n s\u1ed1 c\u00e1c \u00e2m so v\u1edbi \u00e2m \u201c\u0111\u00f4\u201d t\u01b0\u01a1ng \u1ee9ng:<\/p>\n\n\n\n
T\u1eeb b\u1ea3ng n\u00e0y ch\u00fang ta th\u1ea5y c\u00e1c h\u1ee3p \u00e2m th\u01b0\u1eddng d\u00f9ng trong \u00e2m nh\u1ea1c l\u00e0 nh\u00f3m ba \u00e2m (n\u1ed1t), ba \u00e2m n\u00e0y t\u1eadp h\u1ee3p th\u00e0nh nh\u00f3m ba n\u1ed1t g\u1ecdi l\u00e0 h\u1ee3p \u00e2m (v\u00ed d\u1ee5 c\u00e1c h\u1ee3p \u00e2m \u0111\u00f4 – mi – sol v\u00e0 sol – si – r\u00ea), t\u1ec9 s\u1ed1 c\u00e1c t\u1ea7n s\u1ed1 ba \u00e2m trong h\u1ee3p \u00e2m t\u1ec9 l\u1ec7 v\u1edbi 4: 5: 6 l\u00e0 nh\u1eefng h\u1ee3p \u00e2m t\u1ea1o n\u00ean c\u1ea3m gi\u00e1c h\u00f9ng m\u1ea1nh, trong s\u00e1ng. H\u1ee3p \u00e2m kh\u00e1c cho c\u1ea3m gi\u00e1c \u0111\u1eb9p \u0111\u1ebd, th\u00e2m tr\u1ea7m, tinh t\u1ebf l\u00e0 c\u00e1c h\u1ee3p \u00e2m la – \u0111\u1ed1 – m\u00ed v\u00e0 mi – sol – si c\u00f3 t\u1ec9 s\u1ed1 c\u00e1c t\u1ea7n s\u1ed1 t\u1ec9 l\u1ec7 v\u1edbi 3 s\u1ed1 10 : 12 : 15. C\u00e1c lo\u1ea1i h\u1ee3p \u00e2m t\u1ea1o th\u00e0nh c\u00f3 c\u00e1c t\u1ec9 s\u1ed1 t\u1ea7n s\u1ed1 c\u1ee7a chung t\u1ec9 l\u1ec7 v\u1edbi c\u00e1c t\u1ec9 s\u1ed1 \u0111\u01a1n gi\u1ea3n nh\u01b0 tr\u00ean t\u1ea1o n\u00ean c\u1ea3m gi\u00e1c \u00eam tai, h\u1ebft s\u1ee9c d\u1ec5 ch\u1ecbu. \u201c\u00c2m lu\u1eadt\u201d \u00e2m giai b\u1ea3y \u00e2m \u0111\u01b0\u1ee3c ph\u00e1t minh \u1edf Trung Qu\u1ed1c kho\u1ea3ng 1200 n\u0103m tr\u01b0\u1edbc C\u00f4ng nguy\u00ean v\u00e0o th\u1eddi vua V\u0169 V\u01b0\u01a1ng nh\u00e0 Chu. V\u1ec1 sau \u1edf Trung Qu\u1ed1c c\u00f2n ph\u00e1t minh quy t\u1eafc h\u1ebft s\u1ee9c \u0111\u01a1n gi\u1ea3n \u0111\u1ec3 t\u00ednh t\u1ea7n s\u1ed1 c\u00e1c n\u1ed1t trong \u00e2m giai, \u0111\u00f3 l\u00e0 ph\u01b0\u01a1ng ph\u00e1p \u201cchia ba k\u1ebft h\u1ee3p t\u0103ng gi\u1ea3m\u201d \u0111\u01b0\u1ee3c ng\u01b0\u1eddi \u0111\u1eddi sau cho l\u00e0 m\u1ed9t ph\u00e1t hi\u1ec7n t\u00e0i t\u00ecnh trong l\u1ecbch s\u1eed \u00e2m nh\u1ea1c. Ph\u01b0\u01a1ng ph\u00e1p t\u00ednh t\u1ea7n s\u1ed1 c\u00e1c n\u1ed1t trong \u00e2m giai theo quy t\u1eafc \u201cchia ba – t\u0103ng – gi\u1ea3m\u201d \u0111\u01b0\u1ee3c th\u1ef1c hi\u1ec7n nh\u01b0 sau: ch\u1ecdn m\u1ed9t d\u00e2y \u0111\u00e0n ph\u00e1t ra \u00e2m \u201c\u0111\u00f4\u201d khi d\u00f9ng c\u1ea3 \u0111\u1ed9 d\u00e0i c\u1ee7a d\u00e2y. C\u1eaft b\u1ecf 1\/3 \u0111\u1ed9 d\u00e0i c\u1ee7a d\u00e2y (\u201cchia ba b\u1ecf 1\u201d) c\u00f2n l\u1ea1i 2\/3, t\u1ea7n s\u1ed1 c\u1ee7a \u00e2m do d\u00e2y m\u1edbi ph\u00e1t ra s\u1ebd l\u00e0 3\/2 t\u1ea7n s\u1ed1 \u00e2m \u201c\u0111\u00f4\u201d, \u0111\u00f3 ch\u00ednh l\u00e0 \u00e2m \u201csol\u201d (n\u1ed1t sol). L\u1ea1i l\u1ea5y d\u00e2y ph\u00e1t \u00e2m sol l\u00e0m g\u1ed1c, t\u0103ng \u0111\u1ed9 d\u00e0i c\u1ee7a d\u00e2y 1\/3(t\u1ee9c \u201cchia ba t\u0103ng m\u1ed9t\u201d) ngh\u0129a l\u00e0 d\u00e2y m\u1edbi c\u00f3 \u0111\u1ed9 d\u00e0i b\u1eb1ng 4\/3 \u0111\u1ed9 d\u00e0i d\u00e2y ph\u00e1t \u00e2m sol, t\u1ea7n s\u1ed1 do d\u00e2y m\u1edbi ph\u00e1t ra ch\u1ec9 b\u1eb1ng 3\/4 t\u1ea7n s\u1ed1 \u00e2m sol, t\u1ee9c d\u00e2y m\u1edbi ph\u00e1t ra \u00e2m \u201cr\u00ea\u201d. So v\u1edbi \u00e2m \u201c\u0111\u00f4\u201d th\u00ec \u00e2m \u201cr\u00ea\u201d c\u00f3 t\u1ea7n s\u1ed1 3\/2 x 3\/4 = 9\/8; sau \u0111\u00f3 l\u1ea1i \u201cchia ba b\u1edbt m\u1ed9t\u201d ta l\u1ea1i \u0111\u01b0\u1ee3c \u00e2m \u201cla\u201d, ti\u1ebfp t\u1ee5c \u201cchia ba t\u0103ng m\u1ed9t\u201d ta \u0111\u01b0\u1ee3c \u00e2m \u201cmi\u201d\u2026Nh\u01b0 v\u1eady b\u1eb1ng c\u00e1ch s\u1eed d\u1ee5ng xen k\u1ebd quy t\u1eafc \u201cchia ba – t\u0103ng – gi\u1ea3m\u201d ta c\u00f3 th\u1ec3 nh\u1eadn \u0111\u01b0\u1ee3c t\u1ea7n s\u1ed1 to\u00e0n b\u1ed9 c\u00e1c n\u1ed1t trong \u00e2m giai theo \u201c\u00e2m lu\u1eadt b\u1ea3y \u00e2m\u201d. T\u00ednh to\u00e1n t\u1ea7n s\u1ed1 theo quy t\u1eafc n\u00e0y so v\u1edbi \u00e2m lu\u1eadt b\u1ea3y \u00e2m, ch\u1ec9 m\u1eafc sai s\u1ed1 nh\u1ecf h\u01a1n 2,5%.<\/p>\n\n\n\n
\u00c2m lu\u1eadt c\u1ee7a \u00e2m giai b\u1ea3y \u00e2m gi\u1ea3i quy\u1ebft r\u1ea5t t\u1ed1t v\u1ea5n \u0111\u1ec1 \u201cgiai \u00e2m\u201d nh\u01b0ng kh\u00f4ng gi\u1ea3i quy\u1ebft \u0111\u01b0\u1ee3c v\u1ea5n \u0111\u1ec1 chuy\u1ec3n \u00e2m \u0111i\u1ec7u, b\u1edfi v\u00ec khi th\u1ef1c hi\u1ec7n chuy\u1ec3n \u00e2m \u0111i\u1ec7u s\u1ebd xu\u1ea5t hi\u1ec7n c\u00e1c t\u1ea7n s\u1ed1 so v\u1edbi t\u1ea7n s\u1ed1 giai \u0111i\u1ec7u g\u1ed1c c\u00f3 s\u1ef1 kh\u00e1c bi\u1ec7t nh\u1ecf. \u0110\u1ec3 gi\u1ea3i quy\u1ebft v\u1ea5n \u0111\u1ec1 chuy\u1ec3n \u00e2m \u0111i\u1ec7u m\u00e0 v\u1eabn b\u1ea3o \u0111\u1ea3m \u0111\u01b0\u1ee3c t\u1ea7n s\u1ed1 c\u01a1 b\u1ea3n c\u1ee7a \u00e2m giai theo \u00e2m lu\u1eadt b\u1ea3y \u00e2m, ng\u01b0\u1eddi ta ph\u00e1t minh quy t\u1eafc \u201clu\u1eadt b\u00ecnh qu\u00e2n m\u01b0\u1eddi hai\u201d. Theo lu\u1eadt n\u00e0y, ng\u01b0\u1eddi ta chia qu\u00e3ng t\u00e1m t\u1eeb \u0111\u00f4 \u0111\u1ebfn \u0111\u1ed1 th\u00e0nh 12 b\u00e1n \u00e2m b\u1eb1ng nhau (b\u00ecnh qu\u00e2n theo 12). T\u1eeb \u0111\u00f3 ta c\u00f3 c\u00e1c \u00e2m giai c\u00e1c b\u00e1n \u00e2m l\u00e0: \u0111\u00f4, \u0111\u00f4# (\u0111\u00f4 th\u0103ng), r\u00ea, r\u00ea#, mi, fa, fa#, sol, sol#, la, sib (si gi\u00e1ng), si v\u00e0 \u0111\u1ed1. (D\u1ea5u # g\u1ecdi l\u00e0 d\u1ea5u th\u0103ng bi\u1ec3u th\u1ecb \u00e2m c\u00f3 d\u1ea5u th\u0103ng \u0111\u01b0\u1ee3c t\u0103ng \u0111\u1ed9 cao m\u1ed9t b\u00e1n \u00e2m; d\u1ea5u b l\u00e0 d\u1ea5u gi\u00e1ng bi\u1ec3u th\u1ecb \u00e2m c\u00f3 d\u1ea5u b gi\u1ea3m \u0111\u1ed9 cao m\u1ed9t b\u00e1n \u00e2m, \u0111\u01b0\u01a1ng nhi\u00ean l\u00e0 v\u00ed d\u1ee5 \u0110o# = Reb vv\u2026). \u1ede \u0111\u00e2y d\u00f9ng thu\u1eadt ng\u1eef b\u00ecnh qu\u00e2n theo ngh\u0129a l\u00e0 trung b\u00ecnh nh\u00e2n, ngh\u0129a l\u00e0 t\u1ec9 s\u1ed1 c\u1ee7a m\u1ed9t t\u1ea7n s\u1ed1 \u00e2m n\u00e0o \u0111\u00f3 v\u1edbi m\u1ed9t t\u1ea7n s\u1ed1 c\u1ee7a \u00e2m \u0111\u1ee9ng li\u1ec1n tr\u01b0\u1edbc \u0111\u00f3 \u0111\u1ec1u b\u1eb1ng nhau. Ng\u01b0\u1eddi ta d\u1ec5 d\u00e0ng t\u00ednh \u0111\u01b0\u1ee3c t\u1ec9 s\u1ed1 n\u00e0y l\u00e0 12\u221a2 = 1,059463. D\u01b0\u1edbi \u0111\u00e2y tr\u00ecnh b\u00e0y t\u1ea7n s\u1ed1 c\u00e1c \u00e2m (n\u1ed1t) trong \u00e2m giai t\u00ednh theo \u00e2m lu\u1eadt b\u1ea3y \u00e2m v\u00e0 \u201clu\u1eadt b\u00ecnh qu\u00e2n theo 12\u201d. So s\u00e1nh t\u1ea7n s\u1ed1 c\u00e1c n\u1ed1t t\u00ednh theo hai \u00e2m lu\u1eadt ta th\u1ea5y ch\u00fang sai kh\u00e1c nhau trong kho\u1ea3ng 0,8%.<\/p>\n\n\n\n
C\u00e1c lo\u1ea1i \u0111\u00e0n nh\u01b0 Pian\u00f4, th\u1ee5 c\u1ea7m (\u0111\u00e0n harpe) c\u00f3 c\u00e1c n\u1ed1t \u1ea5n \u0111\u1ecbnh \u0111\u1ed9 cao theo lu\u1eadt \u201cb\u00ecnh qu\u00e2n theo 12\u201d, c\u00f2n \u0111\u1ed9 cao c\u1ee7a s\u00e1o \u0111\u1ed3ng c\u00f3 \u0111\u1ed9 cao c\u00e1c n\u1ed1t theo \u00e2m lu\u1eadt b\u1ea3y \u00e2m. Do c\u00e1c n\u1ed1t c\u1ee7a hai lo\u1ea1i \u00e2m giai c\u00f3 t\u1ea7n s\u1ed1 kh\u00f4ng kh\u00e1c nhau nhi\u1ec1u n\u00ean c\u1ea3 hai lo\u1ea1i nh\u1ea1c kh\u00ed \u0111\u1ec1u c\u00f3 th\u1ec3 ho\u00e0 t\u1ea5u v\u1edbi nhau trong d\u00e0n nh\u1ea1c.<\/p>\n\n\n\n
T\u1eeb kho\u00e1: \u00c2m nh\u1ea1c; T\u1ea7n s\u1ed1 \u00e2m;\u00e2m giai; \u00e2m lu\u1eadt b\u1ea3y \u00e2m.<\/p>\n\n\n\n
<\/p>\n\n\n\n\n\n\n","protected":false},"excerpt":{"rendered":"
Ch\u00fang ta \u0111\u1ec1u bi\u1ebft \u00e2m thanh l\u00e0 do ch\u1ea5n \u0111\u1ed9ng sinh ra, \u00e2m thanh cao hay th\u1ea5p l\u00e0 do t\u1ea7n s\u1ed1 c\u1ee7a ch\u1ea5n \u0111\u1ed9ng quy\u1ebft \u0111\u1ecbnh. N\u00e9t \u0111\u1eb9p c\u1ee7a m\u1ed9t kh\u00fac nh\u1ea1c l\u00e0 \u201cgiai \u0111i\u1ec7u\u201d, l\u00e0 s\u1ef1 ph\u1ed1i h\u1ee3p l\u1eabn nhau gi\u1eefa nhi\u1ec1u \u00e2m thanh v\u1ec1 \u0111\u1ed9 d\u00e0i, c\u01b0\u1eddng \u0111\u1ed9 ho\u1eb7c ph\u00e1t ra \u0111\u1ed3ng th\u1eddi […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_disable_autopaging":false},"categories":[15,9],"tags":[],"class_list":["post-7615","post","type-post","status-publish","format-standard","hentry","category-hoi-dap-khoa-hoc","category-toan-hoc"],"_links":{"self":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts\/7615","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/comments?post=7615"}],"version-history":[{"count":0,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts\/7615\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/media?parent=7615"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/categories?post=7615"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/tags?post=7615"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}