Audacity Trumpet Spectra

Discussion in 'Trumpet Discussion' started by Sethoflagos, Apr 18, 2015.

  1. Sethoflagos

    Sethoflagos Utimate User

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    A while ago tjcombo posted this image of the spectral plots of various instruments playing concert Bb, as given by the freeware programme Audacity.

    [​IMG]

    Well, I downloaded Audacity, got it adjusted to what I think are the same settings and tested it on my menagerie. Same concert Bb, all at similar volume and same mouthpiece (DW 2W). Surprised (a bit) at the differences.

    Severinsen:

    [​IMG]

    Sovereign Studio

    [​IMG]

    6335HS II

    [​IMG]

    Wild Thing

    [​IMG]

    Does anyone have the faintest idea what sort of conclusions can be drawn from plots like these. Gut feel is that any peaks below -48dB and beyond 10,000 Hz may be irrelevant. But I can't help sort of liking the look of the plot for the Wild Thing. I am getting on pretty well with that instrument at the moment.
     
  2. Flugel52

    Flugel52 Pianissimo User

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    Wow, really interesting stuff, Seth. Thanks for posting. I'll have to find time to try this with my heard, too. Do the graphs reflect what your ear tells you about the individual horns - i.e., darker, brighter, responsive, etc? The Wild Thing chart seems to support what a friend has always told me about his Wild Thing. Nice work!

    Steve
     
  3. treble_forte

    treble_forte Pianissimo User

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    The player-instrument interaction is too variable to draw definitive conclusions, in my opinion.
     
  4. Sethoflagos

    Sethoflagos Utimate User

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    I've really no idea. I see differences in the graphs, but whether or not they 'explain' perceived differences is a different matter. If they say that most of the sound energy is focused around the core with the Yamaha, but spread further up the harmonics for the Wild Thing then I can relate that to the different sounds I get out of them. The Yamaha feels 'purer', the Wild Thing 'richer'. I don't think the Sovereign and Severinsen are particularly fond of the mouthpiece I'm currently using.
     
  5. rowuk

    rowuk Moderator Staff Member

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    Well, if we consider that acoustic power has to come from somewhere (and everything purple is energy), the Wild Thing needs more energy to play it or it is MUCH more efficient (don't believe that). I would also read that it has a completely different bell shape that reinforces the highest overtones.

    Seth, if it wasn't you, I would also assume that the microphone was substantially closer to the Wild Thing bell than with the others.

    Maybe we can entertain the idea that the more efficient the instrument is, the more "softly" we play it to match microphone level and that decreases the overtone strength. It certainly would line up with my experience. It also justifies multiple instruments to allow a desired palette of colors for a given volume.

    Oh yeah, don't discount the octave above 10khz. While we maybe don't have great hearing up there, there are sum and difference (resultant) tones that end up in the more easily heard octaves.
     
  6. Sethoflagos

    Sethoflagos Utimate User

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    Different bell shape and pretty thin metal so I certainly buy the last bit. Don't forget though that it's a logarithmic vertical scale so a peak at -12 dB has 1,000 times as much power in it as a peak at -42 dB. The extra few dB the Yamaha has on the 3rd, 4th and 5th harmonics is probably far more significant to overall efficiency than the Wild Thing's extended tail. 10 times diddly-squat is still diddly-squat.

    Don't give me too much credit here! I tried to get the samples roughly similar but no more than that. I was actually more interested in the overall shape than in absolute values. Like how the Severinsen and Sovereign traces look more irregular and fade suddenly after the sixth harmonic.

    Never averse to a constructive justification for N+1!

    Actually, I'm quite chuffed to be churning out a few microwatts at C10!
     
  7. rowuk

    rowuk Moderator Staff Member

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    Fine, the upper harmonics are at a low level, but on any trumpet, the efficiency up high is very low AND there are a lot of factors that fight sound propagation of high notes. Naturally, the mics level increases/decreases to the square of distance, so closer in a moderately dead environment can change a lot! Another factor is that those highest tones are VERY directional. That means that a variance of just a couple degrees microphone off access can skew the reading dramatically.

     
  8. tjcombo

    tjcombo Mezzo Forte User

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    Wondering how hard you were blowing Seth? There were some interesting remarks in this reference provided by Rowuk a week or two back... Brass instrument (lip reed) acoustics: an introduction
    Mention is made that, at low volumes when playing higher notes, that the lips flap around in a sinusoidal manner whereas at higher volumes they open and close causing clipping and greater harmonic content. Maybe the Wild Thing spectrum was due to the way that the Wild Thing plays you?

    It'd be interesting to try exciting the horn with a signal source so that input level could be accurately measured along with output and see if some sort of efficiency could be measured - looking to compare this with how the horn feels to blow.
     
  9. rowuk

    rowuk Moderator Staff Member

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    I think to do this accurately we need a couple of things:
    1) a fixed microphone position (clip mic?) directly on axis of the bell
    2) using the VU meter in Audacity, very close to the same volume
    3) 100% accurate tuning of the note(s) in question - even a slight lip up or down would dramatically affect the overtone spectrum
    4) to use a transducer instead of lips is fine, we need to then tune for impedance maximum across the diaphragm
    5) We need a break between horns for our brain - similar to bread during wine testing. Direct comparison does not allow for us to reduce prejudice.

    Perhaps it would be better to play a 1 minute tune and average the entire spectra to compare? The differences would average better


    This topic was the subject of a dissertation by Dr. Frank Hanson:
    http://facstaff.uww.edu/hansonf/uww/Research_files/Hanson_DMA Document.pdf

    Remember this was 1988 and technology was not pocket sized like it is today. I remember Monette putting it on his website sometime in the 90s.
     
  10. Sethoflagos

    Sethoflagos Utimate User

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    Closer to f than mf. I was looking for a bit of colour.

    Exactly!

    Mechanically the big difference with the WT is that due to the bell shape (and to a lesser extent the 0.470" bore) there is substantially more air in the air column. About 15% more than the others, receiver to bell rim when I measured it. Since I got it (over 10 years ago) I've sensed it had more of the feel of a big bore cornet or even a small horn. This might be why it seems to work so well with the larger cup volume of a Wick no letter. And if it's a good acoustic match for the piece I feel most comfortable with, then maybe it's a good acoustic match for me. It certainly lights up very easily for me, and I do feel that it plays me. Happy to let it :-)
     

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