BA , 1 Basic Frequency Analysis of Sound Contents: Frequency and Wavelength Frequency Analysis Perception of Sound

BA , 2 [Hz] Frequency Frequency Range of Different Sound Sources

BA , [Hz] Frequency Audible Range

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

BA , k2 k5 k10 k Frequency, f [Hz] Wavelength,  [m] Wavelength and Frequency

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

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

BA , 8 Imaginary Source Source Reflection of Sound

BA , 9 Basic Frequency Analysis of Sound Contents: Frequency and Wavelength Frequency Analysis Perception of Sound

BA , 10 p LpLp time Frequency time p p LpLp Frequency LpLp Waveforms and Frequencies

BA , 11 p LpLp time Frequency time p p LpLp Frequency LpLp Typical Sound and Noise Signals

BA , 12 Fast Slow Impulse 87.2 RMS Peak Time p Frequency LpLp LpLp Time p Filters

BA , 13 B 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

BA , 14 01k2k3k4k5k6k7k8k9k10k B = 400 Hz Linear Frequency Axis (primarily used in vibration analysis) k2k4k16k8k 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

BA , 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

BA , L L Frequency [Hz] Frequency [Hz] B = 1/1 Octave B = 1/3 Octave 3 × 1/3 Oct. = 1/1 Oct.

BA , 17 Band No.Nominal Centre Frequency Hz Third-octave Passband Hz Octave Passband Hz – – – – – – – – – – – – – – – – K 1.25 K 16 K 20 K 8910 – – – 17.8 K 17.8 – 22.4 K 11.2 – 22.4 K Third-octave and Octave Passband

BA , 18 L Frequency [Hz] 1/1 Octave 1/3 Octave The Spectrogram

BA , 19 Basic Frequency Analysis of Sound Contents: Frequency and Wavelength Frequency Analysis Perception of Sound

BA , 20 Infra AudioUltra KHz Frequency Sound Frequencies

BA , dB k2k5k10k20 k Frequency [Hz] Sound Pressure Level Threshold in Quiet Limit of Damage Risk Threshold of Pain Speech Music Auditory Field

BA , 22 Sound pressure level, L p (dB re 20  Pa) Phon Hz100 Hz1 kHz10 kHz Frequency Equal Loudness Contours for Pure Tones

BA , 23 Change in Sound Level (dB) Change in Perceived Loudness Just perceptible Noticeable difference Twice (or 1/2) as loud Large change Four times (or 1/4) as loud Perception of Noise

BA , Hz1001 kHz10 kHz 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

BA , k10 k L p [dB] A B C D AB + C D Lin. Frequency [Hz] k2 k5 k Frequency Weighting Curves

BA , k10 k L p [dB] A-weighting Frequency [Hz] k2 k5 k  L = 8.6dB Calibration and Weighting!

BA , 27 Fast Slow Impulse 87.2 RMS Peak Weighting Use of Frequency Weighting

BA , 28 Fast Slow Impulse RMS Peak n Serial Analysis

BA , 29 Fast Slow Impulse RMS Peak n Parallel Analysis

BA , 30 Fast Slow Impulse 87.2 RMS Peak Weighting 1/1, 1/3 oct k2k4k8kLA dB1/3 Octave Analysis The Sound Level Analyzer

BA , 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

BA , 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

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