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    EEVblog #820 – Mesh & Nodal Circuit Analysis Tutorial

    EEVblog #820 – Mesh & Nodal Circuit Analysis Tutorial

    Dave explains the fundamental DC circuit theorems of Mesh Analysis, Nodal Analysis, and the Superposition ...

    • Nick

      Audiophiles are going to hate you… For the rest of us, job well done and thanks for sharing. By the way, the aboriginal pattern you (short of) have selected is really great.

      One question: How did you mount the panels on the wall? Did you just hang them like a normal framed picture or did you fix them rigidly?

      • http://www.eevblog.com EEVblog

        Just used standard picture hangers, the type with the angled nail.

    • Phil Reynolds

      Old recording that’s been waiting to be released or misdated at the end?

      Good one, though – showing it needn’t be expensive to improve the acoustics of a room.

    • http://wardyprojects.blogspot.com Adam Ward

      Nice hack, and artistic too. I noticed that those jellyfish on the aboriginal pattern material look a lot like RGB LEDs, so it’s topical too!

      Did you find that it makes the room look darker with them installed? How about trying white material?

      But they definitely work, that echo dropped right off when recording on the handycam’s microphone. I didn’t notice such a pronounced effect on the studio mic test but perhaps that has some built-in echo compensation?

      If it improves your own enjoyment of recording in that room then that’s reason enough to build it, the subsequent increase in recorded quality is a big bonus, not that I ever noticed much echo on the AmpHour show.

      Awesome build.

      • http://www.eevblog.com EEVblog

        You didn’t notice much echo on TheAmpHour because I have used large pillows from the lounge room up until now. So they were effectively doing the same thing as these new panels. Having to move them in for each show was a real pain.

        • http://kj6ead.hackhut.com KJ6EAD

          Those panels ARE pillows on the walls, engineered pillows.

          • http://www.eevblog.com EEVblog


    • Uncle Vernon

      What no egg cartons?

      Just a tip though. Fit a couple of low profile rubber bump-ons to the bottom edge at the rear of each panel. It will dampen out any resonance from the inevitable monster exhaust drive-bys and other LF noise.


      • http://www.eevblog.com EEVblog

        I live in a quiet cul-de-sac, we don’t get doof-doof drive-bys!

    • Rasto

      How have You come up to, what frequency and how much do You need to damp them? Did You use fast furier on Your voice on the osciloscope?

      • http://www.eevblog.com EEVblog

        I didn’t go to that much effort. I simply added as many panels as I could, with the best absorbsion material I could get, and it worked a treat.

    • http://www.waltec.nl Qno

      Hi Dave,

      Nice blog.

      Wouldn’t it be easier to shield the mike from the room echo or use a mike you can attach to your ear to place it near your mouth (Apollo 13 style).

      For the panels to have even more effect lift one corner a bit from the wall so sound, not absorbed by the panel, is reflected away from you.

      Did you do anything about the ceiling or floor?
      Carped on the floor helps also.
      A few squares of polyester wool on the ceiling strategically placed will also help.

      • http://www.eevblog.com EEVblog

        You can’t really shield a mic from room echo, unless I surrounded my head with pillows.
        I could use a headset mic, but they generally aren’t as good a quality as my studio mic, and they rely on the large signal to noise ratio of having the mic very close, so echo is a still problem you really have to solve at the source.

    • xles

      Very nice build!

      One thought though, do you think it’d work with stretched canvas rather than whatever fabric you’re using?

      My lab will do canvas printing (like many labs do these days) you see, and for me, having panels in the form of huge photographs would be rather neat since I consider myself a photographer (amateur, but still).

      • http://www.eevblog.com EEVblog

        You can buy commercially printed artwork sound panels, but I don’t know if they use canvas or cotton fabric like I’m using.
        As long as it’s got some form of open weave and the image isn’t painted on solid it should work.

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    • huh

      Great job, Dave. Very instructive!

      Don’t worry if the panels bulge. If they do it’s actually much better because this somewhat breaks the room symmetry a little. The secret in sound proofing is killing repeated wave bounces, which is what you get in a room with parallel walls (ie almost all rooms). Most professional sound panels are built with have irregular surfaces so that the sound waves that are not absorbed won’t bounce all in the same direction but are dispersed as much as possible.

    • Birdtronics

      Well done Dave, you’ve got me thinking about another use for that Acoustisorb material… I have a number of spectrum analyzers, signal generators, etc with rather noisy rear-mounted fans on my bench. The noise bounces off the smooth wall and comes right back at me. I thought they might be quieter if I put some padding on the wall behind the fans, so I did an experiment with some bath towels on the wall. The noise in the room dropped about 2db, which was noticeable, but not as much as I had hoped for. The material you used would no doubt be better.

      By the way, I heard a lot of what sounded like birds in the background on this video. Do you have pet birds in the house, or was that from outside. Whatever sound it was, the absorbent didn’t suck it up!

      • http://www.eevblog.com EEVblog

        This stuff is also designed to go around machinery to reduce the noise, so would likely work as good as anything for what you want.
        The bird are outside and are in most of my videos. My area is teaming with native wildlife. I get crickets and frogs in the videos too.

    • Chamon

      I discovered your blog a little while ago and been watching all your videos slowly. Great iniciative, great tips, great videoblog!

      I’ve been in acoustics for 5 years now and I can tell you, you did a very good job! It’s actually the correct solution to your problem, although if you’d allow me to add a few things:

      – It’s really good that you didn’t press that material. The ideal thing is that it doesn’t compress too much, otherwise it looses its resilient properties and there goes the absorption capacity!

      – You did the best possible thing about the material thickness. You’re in a voice recording studio, bass is really not your problem (specially that your room is small). Furthermore, this type of panel really doesn’t absorve much low frequencies, even when very thick. If necessary, bass traps on the corner are the way to go.

      – To optimize performance, you could use a panel on the ceilling (right above you) and a diffuser, instead of an absorver, behind you. Although, you already have really good results, that’d be just fixing what is already good.

      • http://www.eevblog.com EEVblog

        Considered a panel on the ceiling, but that idea got a WAF figure of about 0.2

    • Raff

      Well done Dave, the difference is really noticable to me anyway. And I’m glad the panels have a high WAF (Wife Approval Factor)!

      • http://www.eevblog.com EEVblog

        WAF – Acronym of the week!

    • Colin

      Hi Dave, good job on the acoustic panels. They are a big improvement! The colour combination was nice as well. Heavy double layer curtains with lots of excess material (so they fold) is another alternative. If you do them in sections, you can retract some as needed to ‘tune the room’. Speech can sound ‘flat’ in a totally reflectionless studio. If you have windows to deal with, curtains are also useful – you get the light back when the recording is done. Older radio studios, used lead sheet inside walls for acoustic isolation. It works amazingly well. I can still remember audio switching relays inside a mixer being mounted in a lead box, to stop the armature clicking from getting into the microphone… Ah, the grande olde days of wireless broadcasting, when there was money to be made. It’s not like that now. Broadcasting has real competition now, and you’re part of it! Keep up the great work, I really enjoy the EEV BLog. Cheers, Colin

    • http://crome.org caleb

      Hey Dave,
      Nice. Just a possible suggestion for somewhat improved performance: don’t put any backing board on the panels, and stand them off a couple inches from the wall. My understanding is that would give more opportunities to catch and absorb sound.

      Definitely, compressing the material would not be a great thing as already mentioned.


    • http://Www.Radiodoneright.com Matt Gholston

      If you really want quality data on exactly what you have done to your room. Download a free RTA program called REW or Room EQ Wizard. Just google it. You should be able to use the mic you have to do the sweeps or a cheap berenger measurement mic would do also.

      Do 2 sweeps one without panels and one with and look at the difference one all frequencies. It will give you real hard data on your improvement.


    • http://www.soundabsorbingpanels.net Jeff

      “White & Nerdy”. Classic Weird Al!

    • http://mixmasteredacoustics.com/ Acoustic Art Panels

      Buy the best acoustic sound panels from the leading online facility.

    • http://www.soundproofingtips.com Jeffery

      Great little hack for us regular folk looking for results and not emptying the wallet. Have you ever tried blankets? Just wondering, as there is no assembly required :)

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