Phase 1a-Measurement

Measurement and Testing of the Physical Response of an Electromagnetically-Prepared piano

The goal of this phase was to gather information about the physical effects of induction by taking measurements in various controlled environments.

I first set a single electromagnet over a custom-built monochord fitted with a single piano string. The monochord was essentially large bracket, extending about 3 feet from bridge to bridge. This bracket was locked down to reduce sympathetic vibrations. Various simple audio signals were sent through the electromagnet, and the resulting string sounds recorded with a single condenser microphone.


The monochord setup


Taking strobe measurements

The next set of measurements involved the full device, set up in a grand piano in one of IRCAM’s project studios. Again, various simple sounds were sent through the electromagnets. I first sent these sounds through all 12 electromagnets simultaneously – this wasn’t particularly useful for testing purposes, but it sounded interesting so I wanted recordings. Next, the same set of audio signals was sent through individual electromagnets placed over several different pitches (medium, low, and very low ranges). In each case the resulting string sounds were recorded with 4 microphones – a stereo pair of condensers set near the open lid, a single condenser set over the activated string, and a contact mic attached to the top of the soundboard.


The testing setup in a grand piano


A good view of the mic placement (the contact mic is in a sound hole)

I have selected some of the more sonically interesting results from these piano tests and posted them in the Audio Examples 2 page.

The resulting measurements were used by Joël Bensoam as he developed his induction algorithm. We hope to soon co-author a paper detailing his results.

Continue on to Phase 1b – Modalys piano