Developing a model to explain and stimulate the perception of sounds in three dimensions David Kraljevich and Chris Dove

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.

Sound, the Listener, and the Environment Pressure waves Diffraction and Reflection Interference Reverberation : Direct Field vs. Indirect Field From “A 3D Sound Primer” 3D/pages/sndPrmGK.html#anchor509080

Pressure waves

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.

Out of Phase Experiment Right channel: slightly out of phase Results: perceived sound coming from the right! Soundforge Hz stereo samples/sec

Zen Clock Experiment 1.Record “silence” 2.Record Bar Resonating 3.Spectral Analysis

Amplitude (dB) vs. time (samples) Amplitude (dB) vs. Frequency (Hz) (FFT)

Signal vs Noise Frequency spectrum of “silent” recording. Computed with a Fast Fourier Transform using 4096 samples. No smoothing windows applied. RMS power = dB silence clock

Time-domain to frequency-domain Spectrum of 6500Hz sine wave Frequency spectra of piano and violin

Our Model Will Include Phase differences Time differences Intensity differences May Include Spectral differences Won’t Include Psychological factors Head movement Moving sources Environmental cues -Reverberation

Spring Research Use of Binaural Head Deeper exploration of Fourier analysis Quantitative treatment of elevation