Music 220A Homework 4

Auditory Streaming

Noah Makow


Questions

Loudness: how much of a change is required before it separates into more than one voice?

I was able to observe the descending pitch line by changing one of the instruments by as little as 3dB.

Register Transposition: shift the octave of one of the tran array elements, do you get a polyphony effect?

Shifting the octave of one of the elements produced a very noticeable (as compared to loudness) descending pitch line/polyphonic effect. The onset of the descending pitch line was much faster than in the loudness example, which took several cycles before becoming noticeable.

Location: try assigning to different channels in the 4-channel space to see if source location is enough for the effect.

Changing the channels of one of the instruments was not enough to produce a polyphonic effect. This may be due to the fact that I was listening in headphones when trying this, and not through a proper four channel set up.

Timbre: experiment with FM parameters index and ratio.

Altering the FM ratio by even very small amounts was enough to produce the polyphonic effect. I found that it seemed to work best by changing one instruments FM ratio by +/-0.2. Changes smaller than that did not produce a very distinct descending line. Altering the FM index also produced the polyphonic effect, although a bigger change was required. The descending pitch line became especially noticeable at a change of around +/-1.0.


My Audio Streaming Illusion

My piece consisted of two distinct sections. The first section experimented with shifting the octave of one of the instruments up by one. The polyphonic effect becomes apparent a few seconds into the pattern. Shifting the octave of one of the instruments produces a very clear polyphonic effect. The second section shifted the pitches of the notes up by 10 midi notes and doubled the FM index for each instrument (from 1.0 to 2.0) to create a distinct change from the first section. Also, I chose to alter the FM ratio, FM index, and loudness of one of the instruments. The loudness was increased by 5dB, the FM ratio was doubled from 1.0 to 2.0, and the FM index was changed from 2.0 to 3.0. I also chose to reset the acceleration before entering the second section, so that it is possible to hear the descending line become prominent as the notes accelerate.


Relevant files