DESIGN AND QUALIFICATION OF A SEMI-ANECHOIC CHAMBER AND INVESTIGATION INTO NOISE CHARACTERISTICS OF A VACUUM CLEANER A THESIS SUBMITTED TO THE GRADUATE SCHOOL OF NATURAL AND APPLIED SCIENCES OF MIDDLE EAST TECHNICAL UNIVERSITY BY CİHAN KAYHAN IN PARTIAL FULFILLMENT FOR THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN MECHANICAL ENGINEERING MAY 2008 Approval of Thesis “DESIGN AND QUALIFICATION OF A SEMI-ANECHOIC CHAMBER AND INVESTIGATION INTO NOISE CHARACTERISTICS OF A VACUUM CLEANER” Submitted by CİHAN KAYHAN in partial fulfillment of the requirements for the Degree of Master of Science in Mechanical Engineering Department, Middle East Technical University by, Prof. Dr. Canan ÖZGEN Dean, Graduate School of Natural and Applied Sciences ___________________ Prof. Dr. S. Kemal İDER Head of Department, Mechanical Engineering Department ___________________ Prof. Dr. O. Cahit ERALP Supervisor, Mechanical Engineering Department ___________________ Prof.Dr. Mehmet ÇALIŞKAN Co-supervisor, Mechanical Engineering Department ___________________ Examining Committee in Charge: Prof Dr. Kahraman ALBAYRAK(*) Mechanical Engineering Department, METU ___________________ Prof. Dr. O. Cahit ERALP (**) Mechanical Engineering Department, METU ___________________ Prof.Dr. Mehmet ÇALIŞKAN (***) Mechanical Engineering Department, METU ___________________ Prof. Dr. Mustafa İ. GÖKLER Mechanical Engineering Department, METU ___________________ Dr. Songül BAYRAKTAR ARÇELİK A.Ş. ___________________ DATE 08 May 2008 (*) Head of Examining Committee (**) Supervisor (***) Co – Supervisor ii I hereby declare that all information in this document has been obtained and presented in accordance with academic rules and ethical conduct. I also declare that, as required by these rules and conduct, I have fully cited and referenced all material and results that are not original to this work. Cihan KAYHAN iii ABSTRACT DESIGN AND QUALIFICATION OF A SEMI-ANECHOIC CHAMBER AND INVESTIGATION INTO NOISE CHARACTERISTICS OF A VACUUM CLEANER Kayhan, Cihan M.S., Department of Mechanical Engineering Supervisor: Prof. Dr. O. Cahit Eralp Co-supervisor Prof.Dr..Mehmet ÇALIŞKAN May 2008 (94 pages) In this study a centrifugal fan is studied for noise characteristics and measurements in a semi- anechoic room. A semi-anechoic room is constructed inside Fluid Mechanics Laboratory of Mechanical Engineering Department has been qualified with respect to ISO 3745 standard. The fan characteristic is obtained as proposed in AMCA standards 210-75, by simply measuring the voltage and current of the motor during operation and calculating the power consumption of the assembly. Noise measurements are taken using two microphones attached to a multi-channel data acquisition and processing system in the semi anechoic room. Several different configurations of the vacuum cleaner with some parts removed or replaced systematically are considered during the noise measurements. Some of the results showed that the damping material placed inside the motor cover is proved to be very effective in noise reduction. Two different damping materials are examined for comparative evaluation. Keywords: Vacuum cleaner, Centrifugal Fan, Noise, Semi- Anechoic Room iv ÖZ YARI YANSIMALI ODA YETERLİLİĞİ VE ELEKTRİK SÜPÜRGESİ GÜRÜLTÜ KARAKTERİSTİKLERİ ÜZERİNE UYGULAMASI Kayhan, Cihan Yüksek Lisans, Makina Mühendisliği Bölümü Tez Yöneticisi: Prof. Dr. O. Cahit Eralp Yardımcı Tez Yöneticisi Prof.Dr. Mehmet Çalışkan Mayıs 2008, (94 sayfa) Bu çalışmada bir fan karakteristiriği ve bu fanın gürültü ölçümü yarı yansımalı bir odada yapılmıştır. Ses ölçümlerinin yapıldığı yarı yansımalı oda ISO 3745 standardına gore tasarlanmış ve ODTÜ Makina Mühendisliği Akışkanlar Mekaniği Laboratuarı’nda inşa edilmiştir.. Fan karakteristği basit olarak AMCA 210-75 standardında öngörüldüğü üzere fan verimi, motor montajı ve motorun voltaj ve akımı ile motor parçasının güç harcamasını hesaplayarak belirlenmiştir. Gürültü ölçümleri iki mikrofon kullanılarak çok kanallı veri toplama ve işleme sistemi kullanılarak yapılmıştır. Elektrikli süpürge ses ölçümleri için bir çok değişik pozisyonda ve konfigürasyonda elektrik süpürgesi parçaları yer değiştirilerek kaşılaştırmalı olarak ses ölçümleri alınmıştır. Sonuçlara gore motor çevresindeki sönümleme malzemesinin gürültü yalıtımında etkili olduğu gözlemlenmiştir. İki farklı yutumlama malzemesi karşılaştırılmıştır. Anahtar Kelimeler: Elektrik Süpürgesi, Santrifüj Fan, Gürültü, Yarı Yansımalı Oda v To My Family, vi ACKNOWLEDGMENTS The author wishes to express his deepest gratitude and appreciation to his supervisor Prof.Dr. O.Cahit ERALP and co-supervisor Prof.Dr.Mehmet ÇALIŞKAN for their continuous help, guide and encouragement through this study. I am grateful to my colleagues, Serkan KAYILI, Kemal ÇALIŞKAN, Ekin ÖZGİRGİN, Tolga KÖKTÜRK, Ertan HATAYSAL, Gençer KOÇ, F.Ceyhun ŞAHİN, Özgür Cem CEYLAN for their friendship, encouragement and support during very difficult and desperate periods my thesis study. I would also like to thank Dr. Songül BAYRAKTAR and Kani TİBET for her guidance and offering facilities of Product Development Laboratory of ARÇELİK A.Ş. This thesis study is supported by TÜBİTAK, with project no 104M405. TÜBİTAK is also acknowledged. I also thank to technicians of Fluid Mechanics Laboratory, Mehmet ÖZÇİFTÇİ, Rahmi ERCAN for their labour. vii TABLE OF CONTENTS ABSTRACT………………………………………………………………………..iv ÖZ…………………………………………………………………………………..v ACKNOWLEDGEMENTS………………………………………………………..vii TABLE OF CONTENTS…………………………………………………………..viii LIST OF TABLES…………………………………………………………………x LIST OF FIGURES………………………………………………………………..xi NOMENCLATURE……………………………………………………………….xiii CHAPTERS 1. INTRODUCTION 1.1. General…………………………………………………………..1 1.2. Revies of Literature……………………………………………...2 1.3. Aim of Thesis…………………………………………………….3 2. SEMI ANECHOIC ROOM 2.1. General…………………………………………………………..5 2.2 General Theory Of Acoustics……………………………………6 2.3 The Inverse Square Law ………………………………………..9 2.4 Theory of Experiment…………………………………………...11 2.4.1 Qualification procedures for Semi-Anechoic Rooms……………………….13 2.5 Theory of Directivity of a Sound Source……………………….14 2.6 Experimental Setup and Results For Room Qualification……...16 viii 2.6.1. Test Apparatus………………………………………………………………16 2.6.2. SET-UP……………………………………………………………………..19 2.6.3. Sample Calculation………………………………………………………….22 2.7 Results…………………………………………………………..25 2.7.1. Estimation of Sound Pressure Levels for Path-1...........................................25 2.7.2. Estimation of Sound Pressure Levels for Path-1...........................................28 3. FLUID MECHANICS OF VACUUM CLEANER.................. 32 3.1. General..............................................................................32 3.2. Vacuum Cleaner Fan Characteristics……………………………33 3.2.1. Determining Fan Characteristics Experimental Setup...................................33 3.2.2. Fan Characteristic Test Results........................................................................37 4. ACOUSTICAL CHARACTERISTICS OF A VACUUM CLEANER 4.1. Experimental Procedure.............................................................40 4.1.1. Experimental Set-Up....................................................................................40 4.2.2. Experimental Procedure...............................................................................44 4.2. Noise Measurement Results……………………………………………….44 5. CASE STUDIES 5.1. Definiton of the Cases...............................................................52 5.1.1. Case 1……………………………………………………………………..52 5.1.2. Case 2……………………………………………………………………..53 5.1.3. Case3…………………………………………………………………….. 54 5.1.4. Case 4……………………………………………………………………..55 5.2. Noise Measurement Results…………………………………...56 5.2.1. Case 1..........................................................................................................56 5.2.2. Case 2..........................................................................................................58 ix 5.2.3. Case 3.............................................................................................................60 5.2.4. Case 4.............................................................................................................61 6. DISCUSSION AND CONCLUSIONS.......................................63 6.1. The Semi Anechoic Room...........................................................63 6.2. Vacuum Cleaner.......................................................................... 64 6.3. Recommendation for Future Work..............................................64 REFERENCES.......................................................................................66 APPENDICES A . SEMI ANECHOIC ROOM..................................................................................68 B. VACUUM CLEANER NOISE DISTRIBUTIONS ............................................80 C. FLUID MECHANIC OF A VACUUM CLEANER.............................................89 D. COMPONENTS OF A VACUUM CLEANER....................................................91 x LIST OF TABLES Table 2.1 Maximum Allowable Deviation of Measured Sound Pressure Levels from Theoretical Levels using Inverse Square Law…………………….9 Table 2-2 The Differences of Measured Sound Pressure Level from Background Sound Pressure Levels (results are in dB)................................................35 Table 2.3 Calculations of q Values According to ISO 3745………………………..36 Table 2-4 Calculation of r0 According to ISO 3745) ………………………………36 Table 2-5 Calculations of Lp Values According to ISO 3745