Sound Quality Measurement

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ahtb0425
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Sound Quality Measurement

Post by ahtb0425 »

I would like to do the experiment "MP3 Squeeze: How Much Compression is Too Much?" but I need to figure out how to determine the results using quantitative means instead of my own opinion. How do you measure sound quality with numbers? I was thinking of using Audacity, but I am not sure what the units of measurement would be. Any help would be appreciated.


[Administrator note: Project link https://www.sciencebuddies.org/science- ... s-too-much]
RHBrockmeier
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Re: Sound Quality Measurement

Post by RHBrockmeier »

Judging sound quality is always going to be somewhat qualitative.
However, in the "Make it your own" section it suggests to use the Audacity (Analyze Menu) Plot Spectrum feature. One other item this can be compared with is the frequency response of the equipment used to playback the music. You might look up several different types of playback devices and compare them to the spectra you have generated.
ahtb0425
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Joined: Mon Sep 03, 2018 10:40 pm
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Re: Sound Quality Measurement

Post by ahtb0425 »

How would I determine which audio file format was the best using the plot spectrum tool? I tested the tool out in Audacity and all that came up was a graph of the frequencies and the amplitudes. I know it all means something, but I don't know what exactly. What am I supposed to be looking for? I'm sorry, I'm just a little confused. You have been very helpful so far!
RHBrockmeier
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Re: Sound Quality Measurement

Post by RHBrockmeier »

You need to compare the uncompressed graph to the compressed for the same selected sample. If parts of the graph are lower on the compressed that means part of the musical content is missing. Most often you will see it in the higher frequencies or very low frequencies, as these are the areas were most playback equipment can't reproduce. Also look at the sensitivity of human hearing and see what it can and can't detect.
For example, I'm getting old enough that much of my high frequency hearing is shot. If a compression process cuts out the very high sounds I won't notice. On the other hand, you are young enough that you might notice a loss of the higher frequencies.
The other consideration is the capability of the playback equipment to reproduce the sound. My amplifier is rated for operation form 10Hz to 65kHz +1/-3 db. I also have speakers good from 15Hz to 23kHz. On the other hand, the earbuds many people use have a much narrower response. You might research common playback equipment to see what they can handle.
ahtb0425
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Joined: Mon Sep 03, 2018 10:40 pm
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Re: Sound Quality Measurement

Post by ahtb0425 »

Do you have any ideas for variations to this project (besides the ones in the "Make It Your Own" section)? Like, is there any additional stuff to test? I need it to be complex enough so that my teacher will approve of this project. (I am a junior in high school.)
RHBrockmeier
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Re: Sound Quality Measurement

Post by RHBrockmeier »

One variation you might look into is getting a group together for a set of A to B comparisons. Then analyze the results with A and B being compressed and uncompressed samples of the same short piece of music.
ahtb0425
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Joined: Mon Sep 03, 2018 10:40 pm
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Help with Title for Science Project

Post by ahtb0425 »

I need help with coming up with a title for my project. I am doing "MP3 Squeeze: How Much Compression is Too Much?", and I am determining the sound quality of various audio files. The title has to be short. Any suggestions will be appreciated. Thank you.
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