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Sylvester McBean
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Here’s my experiment: I have a wine glass half full of water. I tap the edge with a metallic object to make a ringing sound. I recently bought a nice microphone and some acoustic software (Spectrum Analyzer Pro Live) and I’m trying to analyze the resulting sound to determine the resonance frequency. My hypothesis was that the resonance frequency would change in a predictable way (albeit not linear, given the shape of the glass) depending on the amount of water in the glass. I’ve linked to a short video of me doing this. I was surprised to find that regardless of the amount of water, the peak was usually the same 4-5 frequencies. There did seem to be a relationship between how hard I tapped the glass and which frequency peaked.
So I guess my question is this: Assuming I was able to standardize the impact on the glass and tap it in exactly the same place with exactly the same velocity each time, what changes would you expect in the resulting sound with respect to the amount of water in the glass? The pitch clearly changes depending on the water, which is why I was surprised to see the same peak frequency numbers. I guess maybe I don’t fully understand the relationship between pitch and frequency. Would you expect the amplitude to change? Logically it seems like the more water in the glass, the less the glass can vibrate and thus the lower the amplitude. Are there any other characteristics that would change with the depth of water? My goal is to come up with a formula that can approximate the water in the glass from the sound alone.
https://www.dropbox.com/s/xt8ij2gs8mdesan/resonance.mp4?dl=0
So I guess my question is this: Assuming I was able to standardize the impact on the glass and tap it in exactly the same place with exactly the same velocity each time, what changes would you expect in the resulting sound with respect to the amount of water in the glass? The pitch clearly changes depending on the water, which is why I was surprised to see the same peak frequency numbers. I guess maybe I don’t fully understand the relationship between pitch and frequency. Would you expect the amplitude to change? Logically it seems like the more water in the glass, the less the glass can vibrate and thus the lower the amplitude. Are there any other characteristics that would change with the depth of water? My goal is to come up with a formula that can approximate the water in the glass from the sound alone.
https://www.dropbox.com/s/xt8ij2gs8mdesan/resonance.mp4?dl=0
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