Developing a model to explain and stimulate the perception of sounds in three dimensions

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Developing a model to explain and stimulate the
perception of sounds in three dimensions

• David Kraljevich and Chris Dove

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Experimental Goal

• Create a model describing how sound waves
  recorded at the position of the eardrum change
  depending on the location of their source.
• Test the model by attempting to synthesize
  directional sounds and evaluate them
  subjectively.

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Sound, the Listener, and the Environment

• Pressure waves
• Diffraction and Reflection
• Interference
• Reverberation Direct Field vs. Indirect Field

From A 3D Sound Primer http//www.northwestern.e
du/musicschool/classes/3D/pages/sndPrmGK.htmlanch
or509080
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Pressure waves
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Two researchers, Headphones, and a Brain Winter
experiments
A sound arriving at the near ear is more intense
and arrives earlier than the sound at the far
ear.

• The speed of sound at room temperature and 1atm
  is 343 m/s
• At most, there will be a 0.7 to 0.8 ms
  difference between the time it takes to reach one
  ear and the other.
• We also predict that they will usually arrive at
  different phases.

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Out of Phase Experiment
Soundforge 4.5. 60 Hz stereo. 44100 samples/sec
Right channel slightly out of phase Results
perceived sound coming from the right!
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Zen Clock Experiment

1. Record silence
2. Record Bar Resonating
3. Spectral Analysis

http//www.serenityhealth.com/zclok_burg.html
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Amplitude (dB) vs. time (samples)
Amplitude (dB) vs. Frequency (Hz) (FFT)
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Signal vs Noise
clock
silence
Frequency spectrum of silent recording.
Computed with a Fast Fourier Transform using 4096
samples. No smoothing windows applied. RMS
power -52.30 dB
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Time-domain to frequency-domain
Spectrum of 6500Hz sine wave
Frequency spectra of piano and violin
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Our Model

• Will Include
• Phase differences
• Time differences
• Intensity differences
• May Include
• Spectral differences

• Wont Include
• Psychological factors
• Head movement
• Moving sources
• Environmental cues
• -Reverberation

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Spring Research

• Use of Binaural Head
• Deeper exploration of Fourier analysis
• Quantitative treatment of elevation

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