Quantifying What You Hear...

[Matt Borland]

Hello again,

Sorry for the delay in responding, I appreciated all your responses, 
but got busy moving and starting a new job and couldn't find time to 
sit down to tap out a good email. I think the one thing you all 
mentioned was that what I intend to work on is not going to be easy. I 
agree completely, but as Gregor mentioned, there is definitely some 
precedence for some of this work and I'm glad that I received such a 
positive response.

In order of reply...

Ric, I agree very much that the language I choose to define some of the 
measurements is going to be very important.  Really all I want is 
something similar to the ISO or ANSI definitions for acoustical terms 
and values. As I mentioned, the RT60 (the reverberation time, defined 
by the time it takes for sound pressure levels to decrease by 60dB in a 
room) is a great example of what I want to do. This is a very practical 
measure that is well defined. The impact this measurement has on speech 
quality (0.6-0.7s preferred), or musicality (1-1.5s preferred) of a 
room is somewhat subjective, but at least there is a solid foundation 
for these kinds of conclusions about what the proper reverberation time 
of a concert hall is.

Dave M, I think you're absolutely right about looking at the shape of 
the spectrum.  This is the acoustical fingerprint, and by using a 
statistical approach to quantifying the shape I think that we should be 
able to determine some of the characteristics of the tone. I put the 
words like bright, muddy, etc.. out there knowing that they are 
probably the hardest things I would try to quantify (compared to them 
the RT60 decay measurements are a walk in the park), but I do think 
that there are possibilities here.

Stéphane, I agree that making the link between the common experience of 
a large group of people is going to be a big project that requires more 
than just a fancy frequency analyser. Gregor mentions psychoacoustics, 
and that is what you're getting at in your post as well. I just hope 
that my quest for the grail is half as much fun as the Python's.

Ric, you're absolutely right that the objective and subjective need to 
be carefully separated. Bad science is not what I'm aiming for, but 
like anyone I could possibly venture down a dark path by accident. 
Hopefully there will be some people to help me not get lost.

Gregor, thanks for the links to the papers, that's exactly what I was 
looking for. I was asking around the lunch table today at the 
acoustical engineering firm I'm working at right now and someone there 
also mentioned the work done by the auto industry (if only I had those 
kinds of research dollars ;). The psychoacoustic aspect of this kind of 
research is something that I think has been ignored, or at least poorly 
presented in the papers I've been thumbing through.

Ed, you mention that a "one size fits all" solution should be avoided 
like the plague and you couldn't be more right. What I hope to do is to 
give the tools to describe tone in a common language, without making 
any conclusions about how "good" your piano sounds. I also agree that 
academic status is definitely not a measure of musical sensitivity. 
It's probably a good time to mention that I'm coming at this with a lot 
of experience with the guitar, and a little bit of guitar building and 
repair. I'm new to the piano, so I'm glad I've got  my supervisor 
Stephen to help me and the people on this list to answer some of my 
questions. The change in tone over time is a great thing to measure, 
how percussive the attack, the sustain, the focus, the decay; all 
really good things. I also agree that the piano is a complex system, 
and that simply measuring soundboards by themselves is not going to 
tell you much. I intend to do my work with fully built and tuned 
pianos. I think that the language that I want to develop should apply 
to fully built instruments, because that's what we hear and that's what 
we play, and anything less is going to be only a description of the 
subsystem without any direct connection to a listener or a player.

David, the mechanical properties are a great place to start as well. My 
background is in mechanical engineering so hopefully I can put some of 
those years of school to good use. I appreciate your definitions, they 
are exactly what I was after. I like your suggestion of manipulating 
hammers, a lot easier than switching out soundboards, and another 
student working on his PhD is looking at hammer string interactions so 
I've got some extra hands to help me out.

So again, thanks for all you responses. This week I'm going to 
formulate some ideas, definitions, and goals and then I'll probably 
post those to get some more feedback. Any more ideas are always 
appreciated.

Thanks,

Matt Borland