1. Acoustics for Libraries By Charles M. Salter, P.E.

2. Introduction Principles ： Site noise considerations Establish noise standards Room acoustic considerations Sound isolation between use spaces Vibration control for mechanical equipment Audio/visual system considerations

3. Sound and noise Please differentiate between sound and noise Define “frequency” SPL (Sound Pressure Level) 音壓 Pa ： Pa – Pascal dB ： dBA ： A-weighting curve has been widely adopted for environmental noise measurement in roadway noise and aircraft noise analyses

4. Sound and noise NC Rating ： ? NC-25:  Loudness of all frequencies must fall at or below the NC-25 curve  以 p6 為例，人對於 NC-25 高頻音 (4kHz) 能 容忍之背景聲音音壓為 ? NC-25 低頻音 (63Hz) 所能容忍之背景聲音音壓為 ?

5. Room Acoustics Physical characteristics of a space for the hearing of directed and reflected sound High level of reflected sound – poor room acoustics  creating unwanted background noise Reverberation  the time required for the sound to be absorbed gradually and reduced below hearing level

6. Room Acoustics Sound absorbing materials  reduce reverberation Multi-purpose rooms ：  Musical activities: longer reverberation is preferred(1.5 seconds – acceptable)  Speech activities: low reverberation is better (<1 seconds – acceptable); too long  causing interference

7. Sound Absorption Sound absorbing materials used in building are rated using the Noise Reduction Coefficient (NRC) Average of sound absorption coefficients from 250 Hz to 2000 Hz (speech frequency)  Perfectly absorptive – NRC = 1.0  Perfectly reflective – NRC = 0.0

8. Sound Absorption Acoustically transparent materials: fabric, perforated metal, and spaced wood slats  acoustically transparent  allowing sound energy to pass through and be absorbed by the material located behind Absorptive materials:  Thicker porous materials in lay-in grid ceiling  Thick glass fiber ceiling tile (or adding acoustic absorption to the space – suspend acoustic baffles

9. Sound Insulation Purpose: reduce intrusive noise; reduce the transmission of sound through solid barriers in buildings 5.1 Principle of sound insulation  Reduction of sound energy from one area to another by absorbing or reflecting – sound transmission loss (TL)  TL of Massive wall > TL of lighter wall  Use of dual panel partition ： increase TL

10. Sound Insulation 5.2 Sound insulation construction  STC (Sound Transmission Class): rating of a wall, floor or ceiling determined by the component of the construction. 傳音等級  5.2.1 Wall construction What is the min STC rating for a conference room and a office? What is the min STC rating for a room having amplified sound systems?

11. Sound Insulation 5.2 Sound insulation construction  5.2.1 Wall construction- What are the considerations for actual construction of sound-rated partition? Air and sound leaks through cracks Air and sound leaks through normal openings Structural connections between double stud partition 雙柱隔板之結構結合情況 Seal both faces of a concrete masonry （混泥 土工程）

12. Sound Insulation 5.2 Sound insulation construction  5.2.1 Wall construction- movable partition- flexible space utilization  What are the types of operable partition? Panel operable wall : better sound isolation (electronic or manual operations) Accordion partitions : for visual privacy

13. Sound Insulation 5.2 Sound insulation construction  5.2.2 Floor construction Two acoustical functions provided by floor and ceiling: airborne sound insulation, and impact insulation Insulation can be upgraded by decoupling ceiling from the structure

14. Mechanical and electrical systems noise control 6.1 Space Planning  Cost-effective noise control technique  Avoid locating mechanical equipment rooms and electrical transformer rooms near spaces that require low background noise level  Floating floor ： neoprene pad + concrete slab

15. Mechanical and electrical systems noise control 6.2 Noise control for main building equipment  Use quietest type fan Down discharge fan Side discharge fan

16. Mechanical and electrical systems noise control 6.2 Noise control for main building equipment  Fan noise transmission Duct borne noise – Breakout noise

17. Mechanical and electrical systems noise control 6.2 Noise control for main building equipment  Absorption of fan-generated noise Provide long duct lengths between fans and the nearest air register serving a room Treat the duct internally with duct liner  Mitigation of air turbulence Using ducts with ample cross-sectional area Keeping duct run straight Round ductwork better than rectangular ductwork

18. Mechanical and electrical systems noise control 6.2 Noise control for main building equipment  Crosstalk Silencers  Duct lagging

19. Mechanical and electrical systems noise control 6.2 Noise control for main building equipment  Variable speed drives and their cabinets should be vibration isolated, and never adjacent to an acoustically sensitive room  Chiller – HVAC (Heating Ventilation Air Condition )

20. Audio-Visual 7.1 Auditoriums, theaters and meeting rooms ----Configuration  Podium or lectern located to the left or right of the screen  Video: maximum depth of the seating – 8 times the height of the screen for video; Height of screen: 最後一排至銀幕之 1/8  Room used for projection: maximum depth seating – 6 or less times the height of the screen

21. Audio-Visual 7.1 Auditoriums, theaters and meeting rooms ----Configuration  30 degrees from the centerline of the screen – limit for seating in the front rows  Width of the screen determined by aspect ratio: 1.3:1 (= 4:3) ( 長 : 寬 )

22. Audio-Visual 7.1 Auditoriums, theaters and meeting rooms ----Configuration  Minimum distance from ceiling: 6 inches – avoid ceiling reflection  Minimum distance from floor: 4 ft  Front projection screen 距離 ?  Rear Projection screen: projector located in a separate room – translucent; better noise control

23. Audio-Visual 7.1 Auditoriums, theaters and meeting rooms ----Configuration  Loudspeakers for sound - should be located as close as possible to the projection  Perforated-type screen: speakers can located behind screen  Solid screen: speakers placed close to ear height

24. Audio-Visual 7.1 Auditoriums, theaters and meeting rooms ----Configuration  Microphone should be selected and located very close to the lecture or performer  Loudspeaker Central cluster: groups all the required loudspeakers at one location (Fig 25), provide best match for audio and visuals Distributed system: works well with low-ceiling room (Fig 26)

25. Audio-Visual 7.2 Teleconference rooms  Audio, or AV  Cameras and video monitors for projection  Video images transmitted over high-speed ISDN telephone  One of two floor plans for effective from camera imaging V-shaped table Curved table

26. Audio-Visual 7.3 Electronic classrooms and training  Distance learning classroom Hybrid of presentation and video conferencing Interaction of local and distant participants Screens – at front and rear of room  Training rooms Different types of training rooms

27. Audio-Visual 7.4 Lighting in AV spaces  Dimmable to allow note taking illumination  Light for speaker – avoid interference with projection images  Dimming system- control “bright” and “dim”  Adequate emergency lighting