1. BA 7660-06, 1 Basic Frequency Analysis of Sound Contents: Frequency and Wavelength Frequency Analysis Perception of Sound

2. BA 7660-06, 2 [Hz] 110100100010 000 Frequency Frequency Range of Different Sound Sources

3. BA 7660-06, 3 110100100010 000 [Hz] Frequency Audible Range

4. BA 7660-06, 4 Wavelength,  [m] Speed of sound, c = 344 m / s Wavelength

5. BA 7660-06, 5 20105210.20.10.05 1020501002005001 k2 k5 k10 k Frequency, f [Hz] Wavelength,  [m] Wavelength and Frequency

6. BA 7660-06, 6 b Diffraction of Sound Example: b = 1 m  = 0.344 m (  f = 1 kHz) Example : b = 0.1 m  = 0.344 m (  f = 1 kHz) b b  b 

7. BA 7660-06, 7 Example: b = 0.5 m  = 0.344 m (  f = 1 kHz) b b Example : b = 0.1 m  = 0.344 m (  f = 1 kHz) b  b  Diffusion of Sound

8. BA 7660-06, 8 Imaginary Source Source Reflection of Sound

9. BA 7660-06, 9 Basic Frequency Analysis of Sound Contents: Frequency and Wavelength Frequency Analysis Perception of Sound

10. BA 7660-06, 10 p LpLp time Frequency time p p LpLp Frequency LpLp Waveforms and Frequencies

11. BA 7660-06, 11 p LpLp time Frequency time p p LpLp Frequency LpLp Typical Sound and Noise Signals

12. BA 7660-06, 12 Fast Slow Impulse 87.2 RMS Peak Time p Frequency LpLp LpLp Time p Filters

13. BA 7660-06, 13 B 0 0 - 3 dB Frequency Ideal filter Practical filter and definition of 3 dB Bandwidth Ripple f1f1 f0f0 f2f2 f1f1 f0f0 f2f2 = Bandwidth = f 2 – f 1 Centre Frequency = f 0 f1f1 f0f0 f2f2 Practical filter and definition of Noise Bandwidth Area Bandpass Filters and Bandwidth

14. BA 7660-06, 14 01k2k3k4k5k6k7k8k9k10k B = 400 Hz Linear Frequency Axis (primarily used in vibration analysis) 2481631.5631252505001k2k4k16k8k Frequency [Hz] Logarithmic Frequency Axis (primarily used in acoustic analysis) B = 400 Hz B = 1/1 Octave Frequency [Hz] L L 1 Filter Types and Frequency Scales

15. BA 7660-06, 15 Frequency [Hz] f 1 = 891 f 0 = 1000 f 2 = 1120 B = 1/1 Octave f 1 = 708 f 0 = 1000 f 2 = 1410 B = 1/3 Octave Frequency [Hz] L L 1/1 Octave 1/3 Octave 1/1 and 1/3 Octave Filters

16. BA 7660-06, 16 50010002000 80010001250 L L Frequency [Hz] Frequency [Hz] B = 1/1 Octave B = 1/3 Octave 3 × 1/3 Oct. = 1/1 Oct.

17. BA 7660-06, 17 Band No.Nominal Centre Frequency Hz Third-octave Passband Hz Octave Passband Hz 123456123456 1.25 1.6 2 2.5 3.15 4 1.12 – 1.41 1.41 – 1.78 1.78 – 2.24 2.24 – 2.82 2.82 – 3.55 3.55 – 4.47 1.41 – 2.82 2.82 – 5.62 27 28 29 30 31 32 500 630 800 1000 1250 1600 447 – 562 562 – 708 708 – 891 891 – 1120 1120 – 1410 1410 – 1780 355 – 708 780 – 1410 40 41 42 43 10 K 1.25 K 16 K 20 K 8910 – 11200 11.2 – 14.1 14.1 – 17.8 K 17.8 – 22.4 K 11.2 – 22.4 K Third-octave and Octave Passband

18. BA 7660-06, 18 L Frequency [Hz] 1/1 Octave 1/3 Octave The Spectrogram

19. BA 7660-06, 19 Basic Frequency Analysis of Sound Contents: Frequency and Wavelength Frequency Analysis Perception of Sound

20. BA 7660-06, 20 Infra AudioUltra 0.020.2220200200020.000200KHz Frequency Sound Frequencies

21. BA 7660-06, 21 960423 140 dB 120 100 80 60 40 20 0 501002005001k2k5k10k20 k Frequency [Hz] Sound Pressure Level Threshold in Quiet Limit of Damage Risk Threshold of Pain Speech Music Auditory Field

22. BA 7660-06, 22 Sound pressure level, L p (dB re 20  Pa) 120 100 80 60 40 20 Phon 0 10 20 30 40 50 60 70 80 90 100 110 120 130 20 Hz100 Hz1 kHz10 kHz Frequency 970379 Equal Loudness Contours for Pure Tones

23. BA 7660-06, 23 Change in Sound Level (dB) Change in Perceived Loudness 3 5 10 15 20 Just perceptible Noticeable difference Twice (or 1/2) as loud Large change Four times (or 1/4) as loud Perception of Noise

24. BA 7660-06, 24 40 20 0 20 Hz1001 kHz10 kHz 40 0 -20 -40 20 Hz1001 kHz10 kHz 40 L p (dB) L p (dB) A-weighting 40 dB Equal Loudness Contour normalized to 0 dB at 1kHz 40 dB Equal Loudness Contour inverted and compared with A-weighting 40 dB Equal Loudness Contours and A-Weight

25. BA 7660-06, 25 0 -20 -40 101001 k10 k L p [dB] A B C D AB + C D Lin. Frequency [Hz] -60 20 k2 k5 k2005002050 Frequency Weighting Curves

26. BA 7660-06, 26 0 -20 -40 101001 k10 k L p [dB] A-weighting Frequency [Hz] -60 20 k2 k5 k2005002050  L = 8.6dB Calibration and Weighting!

27. BA 7660-06, 27 Fast Slow Impulse 87.2 RMS Peak Weighting Use of Frequency Weighting

28. BA 7660-06, 28 Fast Slow Impulse RMS Peak 87.2 321n Serial Analysis

29. BA 7660-06, 29 Fast Slow Impulse RMS Peak 87.2 321n Parallel Analysis

30. BA 7660-06, 30 Fast Slow Impulse 87.2 RMS Peak Weighting 1/1, 1/3 oct 1252505001k2k4k8kLA 20 40 60 80 100 dB1/3 Octave Analysis The Sound Level Analyzer

31. BA 7660-06, 31 L [dB] Frequency [Hz] 1/1 Octave 1/3 Octave L A [dB(A)] L B [dB(B)] L C [dB(C)] L D [dB(D)] L Lin. [dB] The Spectrogram and Overall levels

32. BA 7660-06, 32 Conclusion Headlines of Basic Frequency Analysis of Sound Basic introduction to audible frequency range and wavelength of sound Diffraction, reflection and diffusion of sound Frequency analysis using FFT and Digital filters Fundamental concepts for 1/1 and 1/3 octave filters Human perception of sound and background for A,B,C and D-weighting Signal flow and analysis in Sound Level Meters

33. BA 7660-06, 33 Literature for Further Reading Acoustic Noise Measurements Brüel & Kjær (BT 0010-12) Noise Control - Principles and Practice Brüel & Kjær (188-81)