科技通信课程教案-2023年10月16日.doc

该【科技通信课程教案-2023年10月16日 】是由【lu2yuwb】上传分享，文档一共【7】页，该文档可以免费在线阅读，需要了解更多关于【科技通信课程教案-2023年10月16日 】的内容，可以使用淘豆网的站内搜索功能，选择自己适合的文档，以下文字是截取该文章内的部分文字，如需要获得完整电子版，请下载此文档到您的设备，方便您编辑和打印。2023年10月16日
Accordingly,wefindthattelephonecircuitsthatrespondwelltothislatterrangeoffrequenciesgivequitesatisfactorycommercialtelephoneservice.
.
Aquantitativewaytoaccountfortheeffectofnoiseistointroducesignal-to-noiseratio(SNR),wemay
definetheSNRatthereceiverinputastheratiooftheaveragesignalpowertotheaveragenoisepower,(dBs),definedas10timesthelogarithm(tobase10),signal-to-noiseratiosof10,100and1,000correspondto10,20,and30dBs,respectively.

Thetelecommunicationsenvironmentisdominatedbyfourimportantsourcesofinformation:speech,music,pictures,
definedasasingle-valuedfunctionoftimethatplaystheroleoftheindependentvariable;ateveryinstantoftime,-dimensional,asinthecaseofspeech,music,orcomputerdata;two-dimensional,asinthecaseofpictures;three-dimensional,asinthecaseofvideodata;andfour-dimensional,,weelaborateondifferentsourcesofinformation.
(1),thespeechcommunicationprocessinvolvesthetransferofinformationfromaspeakertoalistener,whichtakesplaceinthreesuccessive
stages:
(1)'smindisrepresentedbyaspeechsignalthatconsistsofsounds(.,pressurewaves)generatedinsidethevocaltractandwhosearrangementisgovernedbytherulesoflanguage.
(2),reachingthelistener'sears.
(3),therebycompletingthechainofeventsthatculminate[达到顶点]inthetransferofinformationfromthespeakertothelistener.
Thespeech-productionprocessmaybeviewedas
aformoffiltering,-sectionalarea,beginningattheglottis(.,theopeningbetweenthevocalcords),thespectrum(.,frequencycontent)isshapedbythefrequencyselectivityofthevocaltract;(.,thedistributionoflong-termaveragepowerversusfrequency)ofspeechapproacheszeroforzerofrequencyandreachesapeakintheneighborhoodofafewhundred
,however,,thetypeofcommunicationsystembeingconsideredhasanimportantbearingonthebandoffrequenciesconsideredtobe"essential",asmentionedpreviously,abandwidthof300to3100Hzisconsideredadequateforcommercialtelephoniccommunication.
(2)Thesecondsourceofinformation,music,originatesfrominstrumentssuchasthepiano,violin,
keyonapiano,,musichastwostructures:,,,musicalsignalsdemandamuchwiderchannelbandwidththanspeechsignalsfortheirtransmission.