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**HELP** Mathematics Senior thesis: Acoustic study of plasma waves

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**HELP** Mathematics Senior thesis: Acoustic study of plasma waves

Postby Moses4525 » Sat Sep 26, 2020 9:52 pm

I recently bought a Sennheiser e602 II Evolution Series Dynamic Bass-drum Microphone in order to studying lower bass frequencies for my mathematics senior thesis... the digital input signal needs to be pretty accurate since I am doing detailed analysis of the acoustical environment. I recently saw online that just plugging the XLR mic into my macbook pro is a stupid idea lol
So my current question is, if I'm only wanting to spend an additional $100-$150 on a pre amp and analog to digital converter, what should I buy to get that reliable digital signal that I can use to study? Or will the signal be accurate enough when just using the e602 II into my macbook pro? I'd appreciate anyone's advice!


P.S. if I get enough replies and help on this forum post, I'll continuing to post updates and questions throughout my study. :)

Thanks in advance!
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Re: **HELP** Mathematics Senior thesis: Acoustic study of plasma waves

Postby Moses4525 » Sat Sep 26, 2020 10:46 pm

Here is my paper describing the device that I will be using as a source of audio for my acoustic study.
https://drive.google.com/file/d/1bBpvED ... sp=sharing
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Re: **HELP** Mathematics Senior thesis: Acoustic study of plasma waves

Postby blinddrew » Sat Sep 26, 2020 11:07 pm

Any semi-decent audio interface will do the job. Mackie, Behringer, Presonus, Tascam and Focusrite all make decent interfaces for less than £100.
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Re: **HELP** Mathematics Senior thesis: Acoustic study of plasma waves

Postby James Perrett » Sun Sep 27, 2020 12:29 am

I must admit that I would have been tempted to use a measurement mic rather than a coloured bass emphasised mic for this project. As Drew says, there are a wide range of decent quality audio interfaces with mic preamps. I would suggest treating the Behringer UMC202 as the minimum standard required. There are slightly cheaper interfaces around but you may actually find higher sample rates useful in this application if you were to use a measurement mic.
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Re: **HELP** Mathematics Senior thesis: Acoustic study of plasma waves

Postby Moses4525 » Sun Sep 27, 2020 12:50 am

James Perrett wrote:I must admit that I would have been tempted to use a measurement mic rather than a coloured bass emphasised mic for this project. As Drew says, there are a wide range of decent quality audio interfaces with mic preamps. I would suggest treating the Behringer UMC202 as the minimum standard required. There are slightly cheaper interfaces around but you may actually find higher sample rates useful in this application if you were to use a measurement mic.

I haven't received the mic yet and could always return it. Could you provide a few links for me to check out?

also what software would you recommend for analysis?
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Re: **HELP** Mathematics Senior thesis: Acoustic study of plasma waves

Postby resistorman » Sun Sep 27, 2020 2:45 am

Bass drum mics have a tailored frequency response for pop music, not science. Better send it back.
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Re: **HELP** Mathematics Senior thesis: Acoustic study of plasma waves

Postby adrian_k » Sun Sep 27, 2020 6:44 am

You haven’t said how/what you intend to record - near/far, loud/soft, environment etc, but I would look at omni directional microphones as they have a more natural bass response than cardioid /hypercardioid specialist instrument mics . As James says a measurement mic seems a better bet - something like this https://europe.beyerdynamic.com/mm-1.html

Re analysis software - what are you wanting to analyse?
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Re: **HELP** Mathematics Senior thesis: Acoustic study of plasma waves

Postby Arpangel » Sun Sep 27, 2020 8:54 am

A measurement microphone is essential, as others have said, the Beyer is a good starting point, but something like the Earthworks measurement series would be preferable IMO given the application and importance of your project, it would be worth spending the extra money.

https://earthworksaudio.com/microphones/m-series/

I can’t emphasise this enough.
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Re: **HELP** Mathematics Senior thesis: Acoustic study of plasma waves

Postby adrian_k » Sun Sep 27, 2020 9:07 am

Actually Arpangel is right. The Beyer is 20Hz to 20kHz, those Earthworks have a much wider frequency response.
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Re: **HELP** Mathematics Senior thesis: Acoustic study of plasma waves

Postby Trevor Johnson » Sun Sep 27, 2020 11:03 am

First of all, I would like to extend my best wishes for your research project.

I read your linked paper and note that you are a student at Eastern Washington University. Looking at the University website, I see that they have considerable resources in Mechanical Engineering & Technology. You said, "doing detailed analysis of the acoustical environment', in which case you need a very controlled acoustical environment, which the University may be able to offer, together with measuring equipment, e.g. measurement microphones, anechoic chamber, etc..

I would see what is available and ask your supervisor for advice. Central Washington University, (I don't know whether Eastern Washington University has), has an anechoic chamber and clearly have expertise in sound measurement: in my experience, universities are usually good at sharing resources, even if just advice. That would be my starting point, rather than at the moment wondering which microphone/interface to buy, as you may not have to.
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Re: **HELP** Mathematics Senior thesis: Acoustic study of plasma waves

Postby rockydennis » Sun Sep 27, 2020 11:17 am

"also what software would you recommend for analysis?"
MATLAB is really the tool of choice for signal processing. It's really a programming environment, so if you've not used it, there's a little bit of a learning curve. There's a signal processing toolbox that provides a lot of the functions you'll use. It's surely installed on the computers on campus and there's a fully featured student edition you can buy ($99 last I checked); some schools provide it for free.
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Re: **HELP** Mathematics Senior thesis: Acoustic study of plasma waves

Postby wireman » Sun Sep 27, 2020 11:26 am

Moses4525 wrote:Here is my paper describing the device that I will be using as a source of audio for my acoustic study.
https://drive.google.com/file/d/1bBpvED ... sp=sharing

You should fix the SI prefix table.
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Re: **HELP** Mathematics Senior thesis: Acoustic study of plasma waves

Postby Logarhythm » Sun Sep 27, 2020 11:53 am

wireman wrote:You should fix the SI prefix table.
Glad I'm not the only one bugged by the stray Ω!

rockydennis wrote:"also what software would you recommend for analysis?"
MATLAB is really the tool of choice for signal processing. It's really a programming environment, so if you've not used it, there's a little bit of a learning curve. There's a signal processing toolbox that provides a lot of the functions you'll use. It's surely installed on the computers on campus and there's a fully featured student edition you can buy ($99 last I checked); some schools provide it for free.
I'd second the recommendation for MATLAB. I'd be surprised if you can't access it in your department, but if not then get in touch with the Physics department as they're likely to have lots of computers with it installed.
It's also fairly likely that one of the departments will run an "introduction to MATLAB" module for undergrads, so that might be worth tracking down if you're new to it.

OriginLab is also pretty good for various types of data analysis. It's not as flexible as MATLAB - more of an Excel on steroids (that undersells it really, but if you can use Excel then you will get to grips with it moderately quickly) - but may suffice for what you need and doesn't have quite such a steep learning curve.

Trevor Johnson wrote: in my experience, universities are usually good at sharing resources, even if just advice. That would be my starting point, rather than at the moment wondering which microphone/interface to buy, as you may not have to.
This is also great advice. My experience has been that people in the university science departments tend to be generally curious and will often loan expertise/kit and potentially their own time too. Make a polite introduction and see where it goes :thumbup:
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Re: **HELP** Mathematics Senior thesis: Acoustic study of plasma waves

Postby James Perrett » Sun Sep 27, 2020 2:25 pm

I'd echo all the recommendations on here.

Matlab is the standard for processing and most universities should have a site licence. There are free alternatives like Gnu Octave and Scilab but I don't know whether they included the DSP processing that Matlab offers. If you are planning on going further in engineering academia you'll find that knowledge of Matlab is almost essential.

You can buy measurement mics for $30 but if you want something properly calibrated then the Beyer mentioned above is probably the cheapest available with individual calibration. The guaranteed extended bandwidth of the Earthworks mics may well be useful though.

I'd also echo the suggestion to see what your university already has - even if you don't have a full acoustics department you may find that someone finds something tucked away from a previous project that would be useful.
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Re: **HELP** Mathematics Senior thesis: Acoustic study of plasma waves

Postby Moses4525 » Sun Sep 27, 2020 11:54 pm

WOW!

First I'd like to thank you all for your responses!

I will contact my advisor and ask if she can help find others that may be able to help in the engineering department. However, there are a lot of limitations for use of lab equipment due to covid. All classes at our university are online at the moment.

if I cant get a measurement microphone provided, buying the mic linked below would be ideal?
https://www.amazon.com/Beyerdynamic-Con ... B000H29LWO
I'll have to look into how to configure a complete set up for testing. I'm very intrigued with anything audio related, but I am still new to the field outside of car audio.

I have taken a MATLAB course (about 5 years ago at a different university) and am currently required to start using Octave this quarter for my numerical linear algebra course.

I need to learn a lot more about how to implement mathematics into all of this... after recording the audio produced by the Tesla coil, in your professional opinion, what would be the ideal route to take for research? I initially wanted to see how an enclosure could better the production of lower frequencies. Many hobbyist that play around with the musical tesla coils always get comments mentioning how cool it would be if there was bass. So that's my justification for wanting to implement an enclosure into the study.

I am almost positive that I will need to consult a professional to help me design an enclosure that would be useful.

Again, anyone's opinions are welcome and greatly appreciated!
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