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HUtiNG DAN QUAN LY, stf DUNG I I T H U C H I E N T H I N G H I E M D O T O C D O • • • • TRUYEN AM TRONG KHONG KHI 1 Muc tieu Thong qua bai thtfc hanh hpc sinh nam dtfpc tinh chat cua nguon am, stf tr[.]
HUtiNG DAN QUAN LY, stf DUNG T H U C HIEN T H IN G H I E M D O T O C • • • II D O • TRUYEN AM TRONG KHONG KHI Ho Tuan Hung TrUdng Dqi hoc sU phqm Hd Noi Muc tieu Thong qua bai thtfc hanh hpc sinh nam dtfpc tinh chat cua nguon am, stf truyen song am khong va hien ttfpng tong hpp song am cpt khong Ly thuyet Am la dang tin hieu bien thien, dtfpc dac trtfng bdi cac dai ltfpng: - Tan sd bien thien khoang 16Hz den 20.000Hz, dai ltfpng dac trtfng cho dp cao cua am Tan so thap ttfdng tfng vdi am tram, tan sd cao ttfdng tfng vdi am bong Dtfdi 16Hz ngtfdi ta gpi la am (hay de am), tren 20.000Hz ngtfdi ta gpi la sieu im - Ctfdng dp cua tin hieu dac trtfng cho dp to cua am Ctfdng dp cua tin hieu md ta tren thi, chinh la bien dp cua dao dpng - So ltfpng hai cua tin hieu dac trtfng cho am sic Die tinh niy cd t h i hieu, vdi mpt tin hieu am bat Id cd the phin tich tin hi|u thinh cac tin hieu cd dang hinh sin vdi bien dp va tin sd khac theo quy luat nhat dinh Thanh phan tin hieu phan tich dtfpc gpi l i hai cua tin hieu, sd ltfpng hai phy thupc vio tinh bat ki cua tin hi|u i m Cd the thi du, hai ngtfdi ndi cd dp to v i dp cao nhtf nhau, nhtfng van phin bi|t dtfpc tieng cua ngtfdi niy vdi ngtfdi l i sd hai cua hai i m A" v = £ ho?cv = > x la khac Ngoai am dtfdc die trtfng bdi cac dai ltfdng lien quan den stf truyen am, hien ttfpng cpng htfdng am Khi truyen am mpt mdi trtfdng nao do, neu sdng am bi phan xa trd lai, thi chung cd the ket hdp vdi va tao nen hien ttfdng sdng dtfng Khi do, ta cd the tim nhtfng vi tri ttfdng tfng vdi bung sdng hay nut sdng Do moi quan he gitfa van tdc truyen sdng vdi btfdc sdng va tan so im, nen ngtfdi ta co the xac dinh mpt dai ltfpng nio biet hai dai ltfdng Chang han de xac dinh van toe cua am truyin moi trtfdng nio dd, ta cd the stf dung he thtic: 3.Thtfchanh Dung cu gom: - Bp nguon xoay chieu, dieu chinh dtfpc tin sd - Gia cd ong thuy tinh - Pittdng cd day keo - Loa di|n - Bp am thoa va bua cao su - Khdp noi dd loa hoic i m thoa Noi loa vdi ngudn am, chpn tan so 500Hz, dung diy keo pittdng di chuyin dng thuy tinh, cho din luc i m nghe dtfdc to nhat Xac dinh vi tri i m nghe dtfdc l i ldn nhat, sau keo pittdng tiep tuc v i tim xem vi tri khac cung nghe dtfdc i m ldn nhat Khoang each cua hai vi tri lien nghe dtfdc to nhat la khoing each cua hai bung sdng Vdi tan so 500Hz, van tdc truyin i m khdng khoang 330m/s, thi \/2 dtfpc se khoang 0,33m Thtfc stf van toe co dung nhtf each xac dinh bang thi nghiem hay khong? Thtfc hien vdi cac tan so khac cua am va xac dinh lai khoang each gitfa hai vi tri nghe to nhat Thtfc hien ttfdng ttf ddi vdi cac am thoa, bang each thay vi tri cua loa bdi am thoa (hai nhanh i m thoa cung nam dpc theo true cua ong thuy tinh) Vidu: ( Vilril (on) 500Hz IV 600Hz 440Hz 20 Vi tri (cm) 495 , Khoing ddi W 32 M 64 m 56 36 IV 319 320 LUU y - Bd tri mi|ng loa each mieng ong thuy tinh khoang v i i mm l i vtfa - Doi vdi am thoa, thtfc hien xac dinh vi tri nghe to nhat, can go vao i m thoa lien tuc de tranh i m bi giam ctfdng dp dao dpng t i t dan ttfdng doi nhanh - De xac dinh vi tri i m nghe ldn nhat dtfdc chinh xac, doan i m nghe rd, hay keo pittdng di chuyen qua lai mpt vi tri de nghe i m to nhat - Trong hai trtfdng hdp, diing loa v i diing am thoa kit qua cd khac ve van toe truyen tinh dtfpc bdi le chiing bit dng cd dp hd khac nen ap suit dng cd thi khac nhau.a TAP CHI THlft Bj