Name: Modular Improvisation Dec 2024 by Dr. M
Duration: 2 min 51 s
Description: Ambient jam of eurorack through SP404 mkii

White noise with a band pass filter sweep panned to one side. The goal is to demonstrate that we hear direction, specifically up and down, encoded onto the frequency spectra of sounds. 

If you close your eyes and try to pinpoint the sound source it should appear to be moving up and down. This is best experienced with stereophonic headphones. 

This example was suggested in chapter 4 of the Master Handbook of Acoustics, Seventh Edition F. Alton Everest; Ken C. Pohlmann

PsychoAcous Demo BP W Noise Sweep Panned

You will hear a linear increase in volume compared with an exponential increase in volume. First a single note is swept Linearly and then Exponentially. Then audio of a trumpet is turned up the same way. Finally both are superimposed on top of each other. 

The image is a screenshot of the audio you are hearing. You will see that it is swept to max volume and then remains there for a couple seconds. 

The volume is controlled by a saw LFO (Doepfer A174-2) into a Linear and then exponential VCA (Doepfer A130-2). Trumpet audio is from the Library of Congress and can be found here. https://hdl.loc.gov/loc.mbrsrs/varsrs.e80613

Linear Versus Exponential Volume Sweep

An experiment suggested by Fletcher found in chapter 4 of the Master Handbook of Acoustics. 

You will hear two oscillators at brought in one after another with frequencies 318 Hz and 168 Hz respectively. Then their volume is increased significantly. If your listening device is loud enough, you will perceive a shift in pitch of the two notes and their frequencies will shift to 300 and 150 respectively. These are an octave apart, and so the sound will change from discordant to pleasing. 

Please always be careful to protect your ears, and do not listen to loud sounds for sustained periods of time.

Modular Improvisation Dec 2024

Dr. M

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