Volume 3, Number 4, December, 1995 - Noise News International

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··C6SOUNO·••PRODUCTION.·INAIROR ·GASES.-DUCTSLOW FREQUENCY JET NOISEIS EASIER TO REDUCE IFCONVERTED TO HIGHFREQUENCYIf the diameter of a gas outletis large, the noise willpeak at low frequency. If the diameter is small, thenoise will peak at high frequency. The lowfrequency noise can be reduced by replacing a largeoutlet with several small ones. The high frequencynoise is increased, but this is more easily attenuated.Principlemixing regionsingle large outletjet streambranchedoutletmixing region238NoiselNews International1995 December
Application with compressed air and steamperforatedplatepacking of poroussound absorptive materialExampleSteam safety valves in industrysometimes have to discharge very largeamounts of steam many times each day.The required large pipes and large outletspeeds produce high level noise withdominating low frequencies. These aredisturbing at great distances.perforatedplatepacking ofsoundabsorptivemateriallilll~~manY smalljet outletsControl MeasureA diffuser in the shape of a perforatedcone and a high-frequency muffler withlow flow resistance are connected to thesteam pipe. The outlet speed is reducedby a factor of four. The total noiseemitted is reduced by about 20 dB. Thehelical muffler absorbs the highfrequencysound generated by the manysmall holes of the perforated cone.diffusersteam pipeexhaust1995 December NoiselNews International 239
Page 1 and 2: Volume 3, Number 41995 DecemberINTE
Page 3 and 4: Editorial StaffG. Mating,JI'.. Mana
Page 5 and 6: What's all the noise about?Noise Ra
Page 7 and 8: Editor's ViewGoing SurfingThis is t
Page 9 and 10: FeatureRegulations for Community No
Page 11 and 12: • To protect the majority of peop
Page 13 and 14: develop a new proposal for the defi
Page 15 and 16: ....~VIr~ZQ~~;- '";;~Q;[Table 4. Ro
Page 17 and 18: lation living close to roads. This
Page 19 and 20: ....III~?t~~S.zQcountry national LA
Page 21 and 22: The last two objectives have been c
Page 23: CONTROLTheillustrations inthisfeatu
Page 27 and 28: Application with ventilationExample
Page 29 and 30: Application with control valves for
Page 31 and 32: accomplished through the use of the
Page 33 and 34: European NewsA. Cops, European Edit
Page 35 and 36: BooksThe Handbook of Hearing and th
Page 37 and 38: For further information contact Deb
Page 39 and 40: Specialized MeetingsThis calendar i
Page 41 and 42: Standards News (USA)*Avril Brenig,
Page 43 and 44: Standards News (USA)*Avril Brenig,
Page 45 and 46: S3 IECrrC 29(Central Office)2 15- 0
Page 47 and 48: consequences of unable to compare a
Page 49 and 50: World Conference CalendarThis calen
Page 51 and 52: Institute NoticesThisDepartment inc
Page 53 and 54: This is the world's mosl advancedda
Page 55 and 56: International INCE Sustaining Membe
Page 57 and 58: DIRECTORY OF NOISE CONTROL SERVICES
Page 59 and 60: IN THE R&D LAB,ON THE TEST TRACK,ON

Volume 3, Number 4, December, 1995 - Noise News International

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