This week I met with my teammates to talk about the specifics of implementing our project. We also received our first parts and are excited to start working on our proof-of-concept for the physical piano interface soon.
Something I thought a lot about, as I am in charge of scheduling the keys, is how often to play them. We know from piano manufacturer Yamaha that a piano’s inner mechanisms allow each key to be pressed up to 15 times in one second. This is limited by an element known as the hammer: it strikes the strings of the piano to create sound. It takes it approximately 1/15 of a second to leave the string after each strike.
Even though we will be working on a digital piano and not an acoustic one, digital pianos are made to imitate acoustic pianos (when on the “piano” setting). Therefore, we can assume that digital pianos can also be approximately played 15 times per second. I first decided that I would be scheduling the keys at 15 Hz. Upon further consideration, I realized that human speech creates phonemes at a far slower rate than 15 per second. I also realized that playing keys at 15 Hz as long as there exists a frequency would result in a “stutter”: instead of “Hello” in 2 syllables, we would hear many syllables. This would render the speech both inaccurate and unintelligible.
I decided that the keys should be scheduled as such: at each time period, we should compare the status of each frequency to its status at the previous time period. These statuses will be encoded as booleans: 0 if the frequency is not heard, and 1 if it is. If the frequency is going from 0 to 1, we will play the key. If the frequency is going from 1 to 0, we will release the key. Otherwise, keys will retain their former position. This should result in acceptable fidelity to human speech. The time periods have not been decided yet; we will experiment with different frequencies to determine the best one for evoking speech.
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