Psychophysics of Intensity

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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

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

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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

Gas Gas Liquid Liquid Solid Solid
Chlorine 206 Alcohol 1168 Lead 1200
Oxygen 313 Benzole 1324 Steel 5200
Nitrogen 336 Water 1407 Crown glass 5300
Hydrogen 1261 Glycerin 1900 Quartz glass 5370
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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