{"interactiveVideo":{"video":{"startScreenOptions":{"title":"What is a Decibel?","hideStartTitle":false},"textTracks":{"videoTrack":[{"label":"Subtitles","kind":"subtitles","srcLang":"en"}]},"files":[{"path":"videos\/files-65a1695769e33.mp4","mime":"video\/mp4","copyright":{"license":"U"}}]},"assets":{"interactions":[{"x":42.669584245076585,"y":64.2023346303502,"width":20.971461959530107,"height":5.021834061135372,"duration":{"from":270.964,"to":271.964},"libraryTitle":"Image","action":{"library":"H5P.Image 1.1","params":{"decorative":false,"contentName":"Image","expandImage":"Expand Image","minimizeImage":"Minimize Image","alt":"Activity : Calculating dB for 2:1","file":{"path":"images\/file-65a17148ac1ec.png","mime":"image\/png","copyright":{"license":"U"},"width":593,"height":142}},"subContentId":"199569c7-da01-434c-bb7b-c5df066f72cc","metadata":{"contentType":"Image","license":"U","title":"Untitled Image"}},"visuals":{"backgroundColor":"rgba(0,0,0,0)","boxShadow":true},"pause":true,"displayType":"poster","buttonOnMobile":true,"goto":{"url":{"protocol":"http:\/\/"},"visualize":false,"type":""},"label":""},{"x":7.658643326039387,"y":42.80155642023347,"width":10,"height":10,"duration":{"from":349.367,"to":350.367},"libraryTitle":"Text","action":{"library":"H5P.Text 1.1","params":{"text":"

The letter after the dB is known as the reference. It is what the comparison is being made against.<\/p>\n\n

For example, in dBm - the reference is exactly 1mW.<\/p>\n\n

So a power of 3dBm means 3dB more than 1mW which means 2x1 mW = 2mW.<\/p>\n"},"subContentId":"41473065-aaf2-41e1-b56b-65b2966b87f6","metadata":{"contentType":"Text","license":"U","title":"Untitled Text"}},"pause":true,"displayType":"button","buttonOnMobile":false,"visuals":{"backgroundColor":"rgb(255, 255, 255)","boxShadow":true},"goto":{"url":{"protocol":"http:\/\/"},"visualize":false,"type":""},"label":"

Click me - dB references<\/p>\n"},{"x":6.564551422319474,"y":19.45525291828794,"width":10,"height":10,"duration":{"from":515.693,"to":517.693},"libraryTitle":"Text","action":{"library":"H5P.Text 1.1","params":{"text":"

Like we described earlier (at 5:50). A reference is needed if you want to use dB to express power of a signal<\/p>\n"},"subContentId":"6f1b9b62-2bac-4bf7-a196-551c1086aed8","metadata":{"contentType":"Text","license":"U","title":"Untitled Text"}},"pause":true,"displayType":"button","buttonOnMobile":false,"visuals":{"backgroundColor":"rgb(255, 255, 255)","boxShadow":true},"goto":{"url":{"protocol":"http:\/\/"},"visualize":false,"type":""},"label":"

Click me - dB reference<\/p>\n"},{"x":6.564551422319474,"y":54.47470817120623,"width":10,"height":10,"duration":{"from":577.038,"to":579.038},"libraryTitle":"Text","action":{"library":"H5P.Text 1.1","params":{"text":"

For us in COM455, amplitude refers to voltage. So the formula with 20 in it should only be used for converting voltage into dB (which is not needed very often). Mostly we deal with power calculations so the formula with 10 is more often used.<\/p>\n"},"subContentId":"d8ed52a8-ef71-41ad-b87a-a213d88acb2e","metadata":{"contentType":"Text","license":"U","title":"Untitled Text"}},"pause":true,"displayType":"button","buttonOnMobile":false,"visuals":{"backgroundColor":"rgb(255, 255, 255)","boxShadow":true},"goto":{"url":{"protocol":"http:\/\/"},"visualize":false,"type":""},"label":"

click me - amplitude vs power<\/p>\n"},{"x":30.63457330415755,"y":21.400778210116734,"width":25.82056892778993,"height":10.50328227571116,"duration":{"from":640.845,"to":642.845},"libraryTitle":"Fill in the Blanks","action":{"library":"H5P.Blanks 1.14","params":{"media":{"disableImageZooming":false},"text":"

See the image 1(a) here<\/a>, if a 2mW signal is being fed to a device which has a gain <\/u><\/strong> of 3db.<\/p>\n\n

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The output power (?) would be *4* mW<\/p>\n"]},"subContentId":"876cf6fe-2dc8-4a21-a17d-853563858c68","metadata":{"contentType":"Fill in the Blanks","license":"U","title":"Test your understanding"}},"pause":true,"displayType":"poster","buttonOnMobile":false,"adaptivity":{"correct":{"allowOptOut":false,"message":""},"wrong":{"allowOptOut":false,"message":""},"requireCompletion":false},"label":"

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Remember we only add or subtract decibel quantities (no multiplication or division)<\/p>\n"},"subContentId":"c4d96657-146e-44b1-b8be-43a8dcce7ece","metadata":{"contentType":"Text","license":"U","title":"Untitled Text"}},"pause":true,"displayType":"button","buttonOnMobile":false,"visuals":{"backgroundColor":"rgb(255, 255, 255)","boxShadow":true},"goto":{"url":{"protocol":"http:\/\/"},"visualize":false,"type":""},"label":"

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Decibels (dB) by themselves represent ratio of two quantities (ususally powers). To give an absolute power of a signal we must use dB with a reference such as - dBm.<\/p>\n","

Decibels are the mythical creatures living in enhanted forests.<\/p>\n"]}],"overallFeedback":[{"from":0,"to":100}],"solvedLabel":"Progress:","scoreLabel":"Wrong answers:","resultLabel":"Your result","labelCorrect":"Correct.","labelIncorrect":"Incorrect! Please try again.","alternativeIncorrectLabel":"Incorrect","labelCorrectAnswers":"Correct answers.","tipButtonLabel":"Show tip","scoreBarLabel":"You got :num out of :total points","progressText":"Progress :num of :total"},"subContentId":"1c91db40-91fe-40d3-bb14-71a0adebc405","metadata":{"contentType":"Summary","license":"U","title":"Great job"}},"displayAt":3}},"override":{"autoplay":false,"loop":false,"showBookmarksmenuOnLoad":false,"showRewind10":false,"preventSkippingMode":"none","deactivateSound":false},"l10n":{"interaction":"Interaction","play":"Play","pause":"Pause","mute":"Mute, currently unmuted","unmute":"Unmute, currently muted","quality":"Video Quality","captions":"Captions","close":"Close","fullscreen":"Fullscreen","exitFullscreen":"Exit Fullscreen","summary":"Open summary dialog","bookmarks":"Bookmarks","endscreen":"Submit screen","defaultAdaptivitySeekLabel":"Continue","continueWithVideo":"Continue with video","more":"More player options","playbackRate":"Playback Rate","rewind10":"Rewind 10 Seconds","navDisabled":"Navigation is disabled","navForwardDisabled":"Navigating forward is disabled","sndDisabled":"Sound is disabled","requiresCompletionWarning":"You need to answer all the questions correctly before continuing.","back":"Back","hours":"Hours","minutes":"Minutes","seconds":"Seconds","currentTime":"Current time:","totalTime":"Total time:","singleInteractionAnnouncement":"Interaction appeared:","multipleInteractionsAnnouncement":"Multiple interactions appeared.","videoPausedAnnouncement":"Video is paused","content":"Content","answered":"@answered answered","endcardTitle":"@answered Question(s) answered","endcardInformation":"You have answered @answered questions, click below to submit your answers.","endcardInformationOnSubmitButtonDisabled":"You have answered @answered questions.","endcardInformationNoAnswers":"You have not answered any questions.","endcardInformationMustHaveAnswer":"You have to answer at least one question before you can submit your answers.","endcardSubmitButton":"Submit Answers","endcardSubmitMessage":"Your answers have been submitted!","endcardTableRowAnswered":"Answered questions","endcardTableRowScore":"Score","endcardAnsweredScore":"answered","endCardTableRowSummaryWithScore":"You got @score out of @total points for the @question that appeared after @minutes minutes and @seconds seconds.","endCardTableRowSummaryWithoutScore":"You have answered the @question that appeared after @minutes minutes and @seconds seconds.","videoProgressBar":"Video progress","howToCreateInteractions":"Play the video to start creating interactions"}}

Working with Decibel units

Harry Maghera