Studying music poses a conundrum: real musicians don’t play consistently, while machines designed to play an instrument in exactly the same way every time may omit the effects of other factors on the music. In this episode, we talk to Sam Bellows about his research into modeling how the musician’s body affects the diffraction and absorption of clarinet music in directivity measurements.
Associated paper: Samuel David Bellows and Timothy Ward Leishman. “Modeling musician diffraction and absorption for artificially excited clarinet directivity measurements.” Proc. Mtgs. Acoust. 46, 035002 (2022); https://doi.org/10.1121/2.0001586
Find out how to enter the Student Paper Competition for the latest meeting.
Read more from Proceedings of Meetings on Acoustics (POMA).
Learn more about Acoustical Society of America Publications.
Music Credit: Min 2019 by minwbu from Pixabay. https://pixabay.com/?utm_source=link-attribution&utm_medium=referral&utm_campaign=music&utm_content=1022
Studying music poses a conundrum: real musicians don’t play consistently, while machines designed to play an instrument in exactly the same way every time may omit the effects of other factors on the music. In this episode, we talk to Sam Bellows about his research into modeling how the musician’s body affects the diffraction and absorption of clarinet music in directivity measurements.
Associated paper: Samuel David Bellows and Timothy Ward Leishman. “Modeling musician diffraction and absorption for artificially excited clarinet directivity measurements.” Proc. Mtgs. Acoust. 46, 035002 (2022); https://doi.org/10.1121/2.0001586
Find out how to enter the Student Paper Competition for the latest meeting.
Read more from Proceedings of Meetings on Acoustics (POMA).
Learn more about Acoustical Society of America Publications.
Music Credit: Min 2019 by minwbu from Pixabay. https://pixabay.com/?utm_source=link-attribution&utm_medium=referral&utm_campaign=music&utm_content=1022
Kat Setzer (KS)
00:06
Welcome to Across Acoustics, the official podcast of the Acoustical Society of America’s Publications office. On this podcast, we will highlight research from our four publications, The Journal of the Acoustical Society of America, also known as JASA, JASA Express Letters, Proceedings of Meetings on Acoustics, also known as POMA, and Acoustics Today. I'm your host, Kat Setzer, Editorial Associate for the ASA.
Today we'll be talking to Sam Bellows about his article, “Modeling musician diffraction and absorption for artificially excited clarinet directivity measurements,” which appeared in the 46th volume of the Proceedings of Meetings on Acoustics and was one of five winners of the POMA Student Paper Competition for the 182nd meeting of the Acoustical Society of America, which took place this past May in Denver, Colorado. This episode is part of a five-episode series highlighting winners of the POMA Student Paper Competition. So, Sam, congratulations, and thanks for chatting with me today. How are you?
Sam Bellows (SB)
01:08
I'm doing well. Thank you. How are you doing?
KS
01:12
Pretty good. Thanks. Um, so first, tell us a bit about yourself. Where are you studying? And what do you research?
SB
01:18
Yeah, of course. So right now, I'm a graduate student at Brigham Young University in the Department of Physics and Astronomy, and my focus is primarily on acoustics and signal processing. My research spans several areas; these include musical acoustics, room acoustics, loudspeaker design, and array signal processing. However, I'm mostly concerned with theoretical modeling, measurements, and applications of source directivities.
KS
01:43
Ok, very interesting. So give us some background on the research of musical instrument directivity. How's it typically studied and how is the information used?
SB
01:51
So directivity describes how sound waves travel from sound sources like musical instruments and speech. Specifically we want to see how loud sounds are in different directions, such as in front, behind, or to the side of the source. Directivity also helps us better understand in what directions acoustic waves are carrying energy. To study it, we usually measure the sound field around a source using a scanning spherical microphone array. The hemispherical lab we use in our lab has 36 microphones. It attaches to a turntable, and in this way, we can sweep out spherical surface with over 2000 sampling positions. Then we can also study directivity by creating theoretical models that we can solve using mathematical and numerical techniques. And with this knowledge and understanding, we can then apply this, for example, we can see how a violin would sound in a concert hall, or how speech travels in an office.
KS
02:45
Well, that's really fun. So what is artificial excitation? And how does it compare to natural instrument excitation?
SB
02:53
So one of the challenges in directivity measurements is that we want our acoustic signal to be as repeatable as possible. However, when we bring in musicians to play, they often change how loud they are with each rotation of our scanning system. So this means we have to do some heavy post-processing techniques to try to compensate for this. One way some researchers have tried to get around this is to artificially excite the instrument. This basically means building some sort of machine that can play the instrument for them. So for example, in our lab, we built a clarinet blower; it's basically like a box that has a cavity with pressurized air. And we have a set of fake lips that we've made from silicone, and then by adjusting the basic, the pressure on those lips to the reed, we can make the clarinet play for us. And some other artificial devices have used, like, loudspeakers or have made even bowing machines for the violin. Natural excitation, on the other hand, is basically just having the instrument played regularly by a human.
KS
03:55
Okay, that all makes sense. That's pretty nifty, those setups. What are the advantages and disadvantages of each?
SB
04:02
So artificial has excitation has the advantage of being more repeatable, and this makes measurements a lot more easy to do. But on the downside, artificial excitation isn't quite realistic in terms of actual playing conditions. The biggest weakness, though, is that it usually ignores the effect of the human body on the source directivity. And this is important because wave effects, like diffraction and absorption, play an important role in directivity.
KS
04:29
Right, so you definitely would want to have the musician's body taken into consideration. So what are musician diffraction and absorption, and how do they play into sound directivity research, particularly with artificial excitation?
SB
04:45
Yeah, so “diffraction” refers to how sound waves bend and interfere when they travel around the musician's body, and then “absorption” refers to how sound energy is absorbed by things like clothing or skin. And both diffraction and absorption are frequency dependent, and so when frequency is low and the wavelength is large relative to the instrument or the human player, they play less of a role. But with frequency being larger and wavelength becoming shorter, these effects become more significant. And so one of our interests is understanding how significant these effects actually are.
KS
05:23
Ah, okay, got it. So tell us about your experimental setup.
SB
05:28
Yeah, so to try to better understand these diffraction scattering effects, we made three different measurements. And the first case we uses our isolated clarinet, played by our blowing machine. And in this case, there's no body, so sound can radiate without needing to bend around a human. Next, to try to simulate a human body, while maintaining the repeatability of an artificial excitation, we basically took our blowing machine and we attached that to a mannequin. This allows a body-like structure that now incorporates some of these diffraction-absorption effects. However, even a mannequin isn't quite like a human being. So our third measurement scenario, we used a, we just had a regular musician come in and play the clarinet. And so we basically had these three different setups to compare directivities between.
KS
06:18
That totally makes sense. So how does the musician’s body end up affecting measurement results? And stemming from that, what is the significance of these findings?
SB
06:28
So we found that the musician’s body actually does have a really significant effect on the directivity and even at lower frequencies. Part of this is because the size of the human body. So, usually, diffraction and scattering effects take place at about a quarter wavelength. So if you think of 110 hertz, which is the note A2, the wavelength will be about three meters. And what's the usual seated human being being about one meter tall, you can imagine that already at that lower frequency, some of these effects can start to take place. And especially at larger frequencies, these effects become even more important. We can get decreased levels of even 20 or 30 DB, which acoustically is very significant. And these results basically tell us that when we're making directivity measurements, we need to figure out some way to incorporate the human body, whether it's actually bringing in a musician or using some sort of mannequin to simulate it.
KS
07:23
So was there anything in particular that you found exciting or particularly interesting in this research?
SB
07:30
Yeah, I mean, I think for me, being able to compare these directivities from these three measurements was really exciting. And sometimes there are some really interesting scattering-diffracting effects that we weren't quite expecting to see. So it was really neat to be able to see these kind of changes between these three measurements.
KS
07:49
That does sound super interesting. So what are the next steps in your research?
SB
07:54
So far, we've basically only applied this to the clarinet. So our next steps are going to be to generalize this to other instruments and see how musician diffraction is important for those directivity measurements.
KS
08:06
Yeah, it'll be interesting to see how things turn out with the other instruments. Well, I wish you the best of luck. Thank you again for taking time to speak with me today about your research. It was really interesting to learn more about your efforts to make experimental setups for studying musical instruments that better reflect what happens when a real person is playing the instrument. I definitely learned a lot. And of course, once again, congratulations on winning the award from POMA
SB
Thank you.
KS
For any students or mentors listening from around the time this episode is airing we're actually holding another Student Paper Competition for the most recent meeting in Nashville. So, students, if you presented at the national meeting, now's the time to submit your POMA. We're accepting papers from all of the technical areas represented by the ASA. Not only will you get the respect of your peers, you’ll win $300, and perhaps the greatest reward of all, the opportunity to appear on this podcast. And even if you don't win, this is a great opportunity to boost your CV or resume with an editor-reviewed proceedings paper. The deadline is January 8, 2023. We'll include a link to submission information on the show notes for this episode.
Thank you for tuning into Across Acoustics. If you would like to hear more interviews from our authors about their research, please subscribe or find us on your preferred podcast platform.