Acoustic Improvements for Spare Bedroom (with a little help from Doug Young)

[SprintBob]

Hi AGF Recording Pros!

I'm at the start point trying to do a reasonable evaluation of the room in my home that is my guitar room and will also serve as my room for recording. Here's some details:

• 12'x13' with 8' tall flat ceilings, all surfaces parallel
• One 30" wide by 72" tall window centered along one wall
• One wall has door going into closet and remainder of wall with three hanging guitars
• One wall has one hanging mandolin, one hanging picture, and shares corner exterior shelf with next wall
• Next wall has adjoining shelf above, window detailed above, and then two hanging guitars, and finally a 3' wide, x 16" deep, x 42" tall closed floor storage cabinet (against the wall)
• Last wall has two exterior shelves with DVD and plastic storage containers, a shelf with books (at around 72" high), a wall mounted flat screen 32" monitor, Yamaha digital keyboard at 22" tall, and two guitars hanging in remaining available open space

In recording with a Zoom H5 portable recorder using the XY capsule mics, I get a degree of low ambient buzz/hum that shows on the H5 screen at a level around -32 dB that tends to not be heard or perhaps is cancelled out once I start playing. I am assuming this could be some type of reflection/summing of ambient noise that the guitar frequencies tend to cancel out or mask to a degree because when I stop playing in a recording and let the guitar fade out, this low buzz comes back in as the guitar fades out.

I recently sent the first recording below to our very generous and helpful AGF'er Doug Young who did some EQ'ing and mixing of the sound file for me and offered back his comments that the room noise seemed to be not excessively bad at first impression. But that buzz/hum certainly seems significant when I monitor the recording environment real time through a set of headphones.

Here is the "raw" recording using the H5 X-Y mics with no EQ'ing, filters, cleanup, or compression at all. This is recorded on a Collings OM1A.



Here it is after Doug took it and edited the front and back and added some EQ mix and compression.



It cleaned it up a lot and most of that background hum/buzz has been minimized. But I would like to see what I can do to improve the acoustics in the room to try minimize post processing in DAW software. So hopefully the raw recording can give you an idea of what I need to address. Would appreciate anyone's feedback on where I might consider starting.

Thanks so much for taking a listen and also a HUGE thank you to Doug for getting me pointed in the right direction as I embark on this recording journey.

[rick-slo]

To compare things first change the clips so that they play back at equal volume. Typical XY hollow sound. Try a spaced pair setup.
Best bet in a room like that is several absorption panels placed on the walls - preferably 4" thick and perhaps 2' X 4' wide and tall.
Experiment as to where to record in the room for a good sound.

[Doug Young]

Rick, he's using the Zoom H5 with built-in mics. He doesn't have a choice of spaced pairs at the moment. The level differences are because one is his raw original track, the other is after I did a pseudo-mastering pass, so naturally raised the levels to CD volume.

To me, the noise is relative. -35db is certainly not pro studio quality, but for a home recording, compared to recording with a pickup, and for sharing on the interrnet, etc, a little noise is not a showstopper. Certainly worth trying to find the source and fix it tho, if you can without going too crazy. Room treatment isn't really about reducing noise, tho. You can eliminate reflections, and get a less hollow sound with room treatment, but noise in a home studio probably comes from some source - fridge, air conditioning, a computer, traffic, lights, etc. It can be pretty challenging to get rid of, and if you have, say, a computer in the room, it will still be there making noise after room treatment - the noise will just be higher fidelity :-)

[rick-slo]

Volume of original is easily raised to match your tweaks and should be done to present a valid comparison.

[Doug Young]

I don't think this was meant to be a scientific comparison of the tone between the two mixes :-) I wouldn't get too involved in comparing them anyway. That was a 1 minute EQ/add reverb/raise the level operation, and listening to it, I could have done better... (the raw track for my mix was an mp3, BTW) The more interesting comparison is where he started from - the pickup/amp recordings from another thread. I think he made a nice improvement over that.

[SprintBob]

Doug is correct in that I posted the two recordings so one could get an idea of the background buzz that I noted above and that in the mixed version Doug provided back to me, it seems that buzz level decreased with the EQ he applied. As stated above, once the music starts in both recordings, the buzz level seems to blend in enough that it is minimized to a substantial degree and then becomes really noticeable again as the music fades out.

The sources of ambient noise coming into that room are typical interior sources (central HVAC, large appliances, TV’s, other human activities) and any ambient outside sources that can get through the exterior facing wall where the window is. The day I recorded the song above it was about as quiet as it could be since I was the only one in the house and all appliances including the HVAC system were off. It was the same condition when I was evaluating the buzz noted.

I made an interesting observation also last night as at first it seemed like the source of the buzz could be coming through the outside window and possibly caused by the travel of sound from an interstate highway about a mile south of our neighborhood. But I then went into a closed closet further in the back of the house and the buzz was still pretty much there.

The buzz could also be a characteristic of the X-Y capsule on the H5. I have new mics coming in this week (Rode NT1A LDC and Shure KSM137 matched pair SDC) and I can setup the SDC mics as a spaced pair going into the H5. It will be interesting to hear the comparison.

FWIW, buzz is probably not the most descriptive term of the actual noise I hear but it’s a convenient phrase to use.

[Doug Young]

I went back to take a closer look at your noise, on the beginning of your recording. One thing that would help is to record some silence - totally silent without any rustling around. Hard to do :-)

But looking at your track in iZotope RX, here's what I see. Here, the X axis is time, the Y axis is frequency and color is volume. I also selected a small area in between some of the vertical spikes (which are you making some noise), and see not horrible -45db RMS level. All that red stuff is background noise - broadband hiss. Some could be mic self noise - you never get rid of it entirely, tho the Zoom mics are likely not a quiet as a good external mic. Also note because this is an mp3, we have no extreme high end. It cuts off above 15KHz. The blue, purple and green is louder, low frequency noise.



in the second screen, I applied a high pass filter, cutting out everything below 50Hz or so. Now you're left with -63db RMS of background noise. That low rumble is the stuff that's hard to get rid of. Traffic, motors (fridge), etc. But you mostly don't need it in a guitar recording anyway, so you just filter it out.



Anyway, I still don't think this is all that bad. There's a reason on recording that they trim off the head and tails and put some pure silence there. Even a pro recording will have some background noise before the music starts - they just get rid of it before release.

[SprintBob]

As we say in Louisiana, You DA man Doug. Thanks so much for the analysis above. It was enlightening for sure.

As a followup, I received my mic kit yesterday (a Rode NT1A and a pair of Shure KSM137's) and spent some time playing around with them. The setup was simple. I was going to play a couple of riffs via the mic into my H5, no I/O effects turned on in the H5. Good ambient conditions in the house with everything off and no one else home.

First up was the NT1A setup aiming at the neck/body junction about 18" away. When I turned the setup on, the room ambient noise level was around -45db to -48dB, a big improvement from a couple of nights ago where it was -32dB to -35dB. Did a couple of mono recording takes, sounds pretty good and balanced.

Second up were the KSM137's setup as an X-Y pair again about 18" away. When powered up, the room ambient level the mics picked up the same as the NT1A. Did a couple of recordings and the biggest impression is that these mics sounded a bit brighter than the NT1A.

So I came to a conclusion that the lower ambient noise level is due to the higher quality (i.e. more expensive) mics I just bought so hey, this is great.

But to really complete the analysis, I needed to duplicate what I did a couple of nights ago recording with the X-Y capsule on the H5. And guess what, the room ambient noise level was the same with the other two mic setups above! And after recording again, the cheaper capsule mics seem to hold their own well against the more expensive mics above but in fairness I have a lot to learn about the new mics.

So what I have seemed to learn about my recording environment is that even when I setup the house for minimum ambient noise production, the actual ambient noise is going to vary daily as there are probably exterior factors that will affect the response of the structure and what leaks in from outside. I'm lucky per Doug's help that my room acoustics are actually pretty good for doing home recording projects and as I learn to use my DAW software and it's edit and EQ/Mix features, I should be able to manage/minimize the ambient noise levels I seem to have at this point (without having to spend a lot of money on acoustic treatments).

This has been fun and educational so far.

[Doug Young]

Yeah, I get my best results when my wife's gone, it's late at night (traffic dies down), and I've gone as far as throwing the breakers on every room in the house except my studio. It's amazing how you just hear the whole ambient level go down.

Room treatment's another thing entirely tho. "Sound proofing", keeping noise from entering or leaving a room is a way to reduce noise. Acoustic treatment on the other hand, is about getting rid of early reflections that make your recordings sound harsh, or room resonances that act like an EQ on your sound. Getting that "studio sound" is what room treatment is all about. Here's a link to Ethan Winer's site http://realtraps.com/ that has lots of good info (He wants to sell you solutions, but there's a lot of educational stuff on the site, too). For acoustic guitar, with close micing, and for casual recording, we can often get away without treatment in a typical furnished room, but room treatment can definitely make a noticeable improvement. All depends on how much time and effort you're willing to put into it.

[SprintBob]

I hear that Doug. Luckily for me, my wife has become an avid bird watcher and she looks for any opportunity to get out with her fellow birdwatching enthusiasts so that presents windows of recording opportunity for me. I do like to go with her sometimes, it's more fun than I expected.

I also have the option if I can't get away from excessive ambient noise levels from whatever source to try recording from my guitars with pickups to my AI of choice via my Tonedexter. I'll start learning how to make Wavemaps in the Tonedexter next week and then give it a shot. I'll try to post samples here when I get some done.

And thanks for the link to the article at the RealTraps website. The article you referenced looks like an excellent primer to start understanding how to evaluate my recording space and surrounding environment.

[Al Acuff]

Real traps have made a huge improvement in the sound quality of my home recordings.

I record in a spare bedroom/office and there's no free wall space so I obtained 4 of the MiniTraps on stands. It's been most educational having the free standing panels to work with. Moving them around and creating different configurations has allowed me to experiment with placement and hear the results.

There's more work to do. My room could still use some bass trapping and ceiling treatment but just 4 of the Mini Trap panels have already made a big difference!

[sdelsolray]

That noise is mostly made up of the self noise of the mics and preamp. As Doug said, such noise is always present even with the quietest mics and preamps. Still, the noise level is a bit high. That can be mitigated by using quieter mics and/or a quieter preamp.