1. Applications of Architectural Acoustics Tufts University – ME 93 September 10, 2015

2. Outline Sound Proofing vs. Acoustical Treatment Concerns addressed through acoustical treatment Materials used in acoustical treatment Measurement tools in acoustic analysis Considerations in small recording spaces Next steps

3. Sound Proofing Reducing sound transmission between spaces Source: Dan Russell, Penn StateDan Russell, Penn State Mass = A+ sound proofing Air Between Two Decoupled Walls = B sound proofing

4. Sound Proofing Achieved with: Mass, Isolated Construction and Tight Closures Cinder blocks for speaker stands, heavy doors Room-within-a-room construction Door, window and wall seals See White: Chapter 18 for more information

5. Acoustical Treatment Designed for correction

6. Acoustical Treatment Designed for a particular purpose and character

7. Acoustical Treatment Designed for recording instruments & ensembles

8. Acoustical Treatment Designed for critical listening and assessment

9. Reflections Any hard surface will likely reflect sound Any hard flat surface that is larger than the wavelength of a particular frequency will likely reflect energy at that frequency and above Frequency 1 kHz Wavelength 1 foot Period 1 ms λ= VfVf

10. Reflections Echoes are distinct reflections where we can pick out the individual occurrences. We start hearing distinct delays around 20 ms Reflections of less than 20 ms can result in comb filtering Comb filter caused by two signals generated1 ms apart

11. Frequency Specific Issues Modes or Standing Waves Can be calculated and mitigated Types of room modes: Axial = 2 surfaces Tangential = 3 surfaces Oblique = 4 or more surfaces

12. Calculating Axial Modes f = n( c / 2D) Frequency of the mode Dimension between the two boundary surfaces Speed of Sound (1130 ft/second) Positive Integer LENGTHWIDTHHEIGHT 1 st Mode 2 nd Mode 3 rd Mode 4 th Mode

13. Frequency Specific Issues Nodes Hard to prevent; move your groove thing

14. Treatment Materials Absorbers Diffusors Reflectors

15. Absorbers Convert acoustical energy into heat The amount of heat generated is marginal Common absorbers Foam Carpet Draperies Soft furniture Large Mammals

16. Absorption Coefficients Measured across the spectrum 0 = perfect reflector1 = perfect absorber Noise Reduction Coefficient = average of four octaves (250, 500, 1k, 2k) We generally want to absorb equally across the spectrum White pg. 169 has coefficients for common materials

17. Decay time

18. Calculating decay time 0.049V f SA 0.161V m SA RT 60 = Sabine’s Equation: V = volume of the space (in cubic feet or meters) S = absorbing surface area (in ft 2 or m 2 ) A = absorption coefficient (in Sabins)

19. Measuring decay time

20. Anechoic Spaces Used for measurement

21. Diffusors Blackbird Studio, Nashville

22. Diffusors Quadratic Fractal Frequency and scatter patterns depend on size/shape

23. Reflectors Parallel Walls Offset/non-parallel designed walls to redirect sound Domes & curves

24. Intentional Reflectors Acoustic shells Kennedy Center – before & after acoustic shell

25. Measurement tools EASE SMAART REW Faber Acoustical

26. Building a small studio

27. Speaker placement 6 ft. Use heavy cinder block speaker stands to decouple from the floor

28. Mix Position 6 ft.

29. Major reflection issues 6 ft. RACK OF CLOTHES Grow more hair Beware of desk reflections

30. Isolation & sound proofing What sounds don’t we want in the recording space? What sounds don’t we want in the control room?

31. Recording Acoustic Instruments Special Concerns Sound proofing Room volume Does the sound have time to develop? Ambient noise floor HVAC Computers and noisy devices Sonic character

32. Safety and Aesthetics Fireproofing is a thing Aesthetics are also a thing If it sounds good, is it good?

33. Work with what you have Check low-end in good quality headphones Look for drastic gestures in your work Just do something and learn

34. Next Steps Fields of acoustics Architectural Acoustics Graduate Programs Internships related to Architectural and Musical Acoustics Job descriptions for careers related to Acoustics Play with free toys, check out additional resources What can you do to optimize your own space?