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2 Preparation Tips Use Powerpoint to add interest (graphs, photos, audio, video) NOT to add boredom or distraction Do not use as lecture notes! No more than 25 words per slide i.e. Use bullet points - max 6 (3 to 4 words each). This slide is what NOT to do !! Minimize use of fancy ‘fly ins’ - Use ‘Appear’ animation for multiple bullet points Use ‘MDA Black’ slide template (Duplicate Slide 7, or go Format/Slide Design) to create contrast for pictures, videos etc Revert to standard non-logo bulletpoint type by pressing TAB Audio/Video Audio/Video Powerpoint links to (rather than embeds) audio/video files greater than 100KB. Place any required audio/video files in “C:\Audio MDA” folder before you insert them. Create this folder on ANY computer you want to edit or present your presentation on. You can use ‘embed’ for presentations with a small no. of audio/video samples (< 10mb total) that don’t require calibration. To embed you need to increase the ‘link file size limit’ (see Tools/Options/General) accordingly before insertion. Presentation Tips To start presentation, Press F5 or go to Slide Show/View Show. Presentation will automatically start from your title page (Page 3) You can black out the screen during presentation by hitting ‘B’ key. Good when you are talking about something not on screen (‘B’ again to reappear) To assist navigation, remember a few key slide nos. Type 32 ‘enter’ to go to slide 32

Design of walls and floors for good sound insulation

The measurement is made in a laboratory by constructing a wall between two specially isolated rooms. By isolating the rooms, sound only travels between the rooms via the test panel. Measurement of Sound Insulation

Measurement and Calculation 5 We measure the sound pressure on both sides of the wall, in 16 frequency bands between 100Hz and 3150 Hz. The results are plotted on a graph and a reference curve adjusted until the number of points below the graph is just less than 32 dB The value of the reference curve at 500 Hz is the weighted sound reduction index (Rw)

Calculation of Rw (single number rating)

Engineering prediction methods 7 For single panels R is simply related to surface mass - m

Relation between surface mass and R 8

Mass Law (single panel) 9

Mass Law (effect of mass) 10 R increases by 6 dB per doubling of surface mass

Mass Law (effect of frequency) 11 Heavy vinyl fabric (5kg/m2) Mass law R increases by 6 dB per octave (doubling of frequency)

Bending Waves 12 At low frequencies λ b > λ x (sound radiation inefficient) At critical frequency λ b = λ x (sound radiation efficient) At critical frequency the wavelength of the wave in the wall matches or coincides with the wavelength of the wave in the air.

Wave length in Plate and in Air 13 Critical frequency

Mass Law (including bending waves) 14 Resonant transmission

Effect of Bending Waves (12 mm Glass) 15 Critical frequency Forced Transmission Resonant Transmission

Effect of thickness (Glass) mm 6 mm 3 mm As glass thickness increases, low frequency R increases But critical frequency decreases Rw 30 Rw 32 Rw 37

Effect of damping 17 Laminated glass reduces the critical frequency dip 6mm glass 6mm laminated glass Rw 32 Rw 39

Orthotropic Panels 18 Thin metal panels are often rolled into trapezoidal profiles to increase the stiffness and hence spanning capacity This is detrimental to their sound insulation because it lowers the critical frequency

Orthotropic Panels 19 fc = 20,000 Hz fc = 250 Hz

20 Foam Core Panels Thin metal skins with foam plastic core

21 Sound Insulation Properties 75mm thick panel with 0.6mm steel skins Rw 26 dB Dilatational resonance frequency

Double Panel Wall 22 Two panels separated by an air gap

Double Panel prediction methods Ideal Double Panels (London, Sharp) fo is the mass-air-mass resonance fl is the knee frequency and is equal to (55/d) Hz

Double wall behaviour

Mass-air-mass resonance

Effect of Cavity Absorption STC 65 STC 55

Flow resistivity Flow resistivity is a good predictor of acoustic absorption performance, the higher resistivity the better. Different types of absorber with same flow resistivity will have same acoustic performance

Effect of Flow resistivity (fibreglass) cavity infill 90mm 12kg/m3 (=4000 Rayl/m) STC 56 cavity infill 90mm 16kg/m3 (=8000 Rayl/m) STC 58 cavity infill 2x90mm 12kg/m3 (=4000 Rayl/m) STC 59 cavity infill 2x90mm 16kg/m3 (=8000 Rayl/m) STC 61

Effect of Connections Sound energy is transferred by the solid stud connection

Methods of isolating wall linings Resilient Sound Isolation Clip Quietzone Acoustic Framing

Resilient fastenings of Linings

Comparison of single and double wall DescriptionThickness (mm) Mass (kg)Rw (dB) 2x16mm plasterboard on 2x100x50 studs kg/m mm Solid concrete kg/m270 32

33 Triple Panel Constructions Three panels separated by two air gaps

34 Lumped Parameter Model

35 Lumped Parameter Model f 0 = 73, 263 Hz First resonant frequency second resonant frequency

Resonant Frequencies 36 f 1 = 64 Hzf 1 = 53, 92 Hz

37 Comparison of Model to Measurements

A 150mm thick concrete wall which by itself will be Rw 50 can be less than Rw 50 if light gypsum board linings are fixed on both sides. The dip at the mass-air- mass resonance can reduce the Rw rating Masonry with attached lining

Comparison of double and triple wall 39 DescriptionThickness (mm) Mass (kg)Rw (dB) 2x16mm plasterboard on 2x100x50 studs kg/m271 2x10mm plasterboard on 100x50 studs 29068kg/m269

Comparison of single double and triple panel walls 40

Cavity Walls R w 56 R w 53 R w 48 R w 63

Sound Insulation Requirements (Residential) 42 CategoryAirborne Insulation High quality Apartments Rw 65 Mid quality Apartments Rw 60 Code Compliance Minimum performance Rw 55

Sound Insulation Requirements (Education) 43 Library /Study Room Class- room Multi- purpose Hall Technology Room Gymn- asium Music Room Technology Room Gymnasium Classroom Multi-purpose Hall Library/Study Room Music Room60

Sound Insulation Requirements (TV and Radio) 44 Required Rw

Impact Sound 45

Measuring Impact Sound 46

Australian Requirements 47

48 Good sound insulation is very important in buildings Criteria can be established for each room in a building based on user comfort Walls and floors can be designed with simple engineering models to meet criteria Understanding the basic principles of sound transmission helps prevent bad buildings Conclusions