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cardioidmicrophonepolarpattern
panoramicmicrophonepolarpattern
PUBLICADDRESSSYSTEMS
Theaimofapublicaddresssystemisthe
communicationofspokenannouncements.The
broadcastingofmusicforentertainmentpurposesis,
whenrequired,doneatalowvolume.
Theabovesystemsaremainlyusedinpublicvenues,
suchasshoppingcentres,railwaystations,hospitals,
sportsandculturalvenues,inwhichevensound
distributionandtheintelligibilityofthemessages
broadcastareapriority.Insuchinstallations,the
dislocationofsingleloudspeakersinrelationtothe
differentfrequenciesisfoundtobeofgreater
importancethatthehighfidelityofthesourcein
relationtothemusicsignal.Thereishowevera
tendencytousehigherqualitycomponentswitha
moreextensivefrequencyresponse.Attentionshould
bepaidtotheacousticcharacteristicsandtheuseof
theenvironment;thesearethefactorsthatwill
determinetheconfigurationoftheentireproject.
Stereophoniccodingofthesignalisnotusuallyused,
giventhatthenumberofloudspeakersandtheir
positionwouldnotallowcorrectreproductionofthe
stereophonicimage.
Anelectricalsoundsystemcanperformdifferent
typesoffunctions:
-Amplificationofsound:inchurches,theatres,
conferencerooms,etc.
-High-leveldiffusion:foraddressingthepublicin
factories,thestreets(inthecaseofassemblies),
distributionofsoundandannouncementsinsporting
venues,communicationfrommovingvehicles.
-Low-leveldiffusion(backgroundmusic):hotels,
offices,shops,supermarkets,waitingrooms.
-Mixed:withbackgroundmusiccombinedwiththe
possibilityofpublicaddressfunctions,calls,
announcements,alarms,etc..
THEMICROPHONE
Themicrophoneisadevicethattransformsthe
variationsinacousticpressureintoelectricenergy,
therebyallowingthetransmissionandamplificationof
sound
.Thisconversionofenergyoperatesonthebasisof
inductivephenomena,inthecaseofribbon
microphones,orcapacityvariation,asinthecaseof
condensermicrophones.Thesetwotypesaccount
forthelargemajorityofprofessionalmicrophones
usedtoday.
Theribbonmicrophoneisthemostcommon,dueto
itsgoodqualityandsolidstructure,thatmakesit
resistanttotheeffectofatmospherichumidity,andallroundperformance.
Duetoitslowvoltageoutput,thecondenser
microphonemustbeusedinconjunctionwitha
preamplifier,whichisusuallyincorporatedintothe
microphoneitself,tolifttheoutputsignalandthereby
giveanexcellentdegreeofsensitivity.Thecondenser
microphoneispoweredeitherbyasmallbattery
(usuallyincorporated)or(ifprearranged)bythe
amplifierbymeansofthesamelinesusedforthe
signal(phantompower).
Theresultsareexcellent,thoughareproducedata
highcost,whichiswhythecondensermicrophoneis
almostexclusivelyusedforhigh-level professional
applications.
Innocaseshouldmicrophonesbeorientedtowards
theloudspeakeroritsscatteringzone,asthiswill
causesoundfeedback.Intheeventofthelatter,lower
amplifiervolume,adjustthetonecontrol,orif
necessary,installagraphicequaliser(orevenbetter,
aparametricequaliser)tofilteroutthefrequencies
causingfeedback.
Whenconnectingthemicrophonetotheamplifier,
prefershort,twin-wireshieldedlines.Microphone
linesshouldbekeptatleast30-50cmfrom
loudspeakerandotherelectricalequipmentlines.If
theselinesareparticularlylong(i.e.>6/8m),connect
themicrophonetoabalancedamplifierinputto
eliminatetheriskofinterference(evenwithlines
dozensofmetreslong).Inthecaseoflonger
microphonelines,itwillbenecessarytouse
microphonepreamplifierswithbalancedlines(inthis
way,distancesofoverakilometrecanbecovered).