| Engineering Acoustics - EEN502 Michael Battaglia Project 1 |
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Part 3 - ObjectiveAssume the receiver is a human listening binaurally. The interaural distance in an adult subject is 17 cm. Repeat the preceding parts for this scenario by ignoring any head shadow effects. Generate the stereo signals appropriate for setups (1) and (2). Solution: Matlab Code For the purposes of this experiment, only setup (2) was implemented: setup (1) is inherent in the design for setup (2). The source can be made to pass through the observer (as setup (1) dictates) by simply specifying the minimum distance between observer and source as zero, or arbitrarily close to zero. In my setup, the left ear is outputted to the left channel alone and the right ear to the right channel alone; this maximizes the binaural effect. At certain settings the signal will seem to pass from right to left rather than from left to right: this could be explained as a result of the subtle phase distortions inherent in the FSK method expressed in part 2. Although the phase distortions are minimized with the phase-locking at observer closest to source approach, and although they are certainly suppressed enough to eliminate a large-scale alteration to the audible frequency, subtle interaural phase distortions may still be present and give the illusion that the sound is actually moving from right to left. However, when the interaural frequency and loudness cues become apparent enough, the signal appears to move from left to right as expected. The proper binaural Doppler effect was most noticeable when the signal was closer to the head and moving more slowly than in the previous examples. The following is a plot of a 10 m source trajectory, a velocity of 5 m/s, and the observer placed in the middle at 5 m from the source origin and back only 1 meter. The frequency being emitted here is 440 Hz. In the above plots, blue represents the left ear and green represents the right ear. For comparison, here is another plot. The following plot reflects a trajectory length of 5 m, a velocity of 5 m/s, and an observer located at 4 m from the left of the start trajectory and 1 m away from the closest point on the line. The frequency being emitted is 1000 Hz. |
