2. Psychophysics of Intensity Amplitude = Loudness Amplitude = Pitch Scales of Intensity –Decibel (dB) Scales Logarithmic (x2 = 3 dB; x1 million = 60 dB) Scaled to Hearing Rang –dB SPL Flat scale, equal at all frequencies –dB HL Scaled to hearing across frequencies

3. dBSPL Source 0Threshold of hearing 10Human breathing at 3 m 20Rustling of leaves 40Residential area at night 50Quiet restaurant 70Busy traffic 80Vacuum cleaner 90Loud factory 100Pneumatic Hammer at 2 m 110Accelerating motorcycle at 5 m 120Amplified music concert 130Threshold of pain 150Jet engine at 30 m 180Rocket engine at 30 m

4. How Does Sound Travel? Impedance Experiment –When was sound loud? Change in spectra? –Why is there a difference? Speed of sound typically 345 m/s in air What does this mean for hearing? –Distance between ears 1 ft ~ 1 ms GasLiquidSolid Chlorine206Alcohol1168Lead1200 Oxygen313Benzole1324Steel5200 Nitrogen336Water1407Crown glass 5300 Hydrogen1261Glycerin1900Quartz glass 5370

5. Sound Mediation Movement of sound may be affected by affected by medium –Distance of travel Sound diffusion –All freq Absorption by media –High freq –Change to greater density Reflection & Scatter –High freq – Change to less density Diffusion –Asymmetrical density Diffraction –Changes shape of the waveform –Low freq