Room Noise

[ukejon]

Traded in my Blue Baby Bottle for a Sennheiser MK4, which has better rear rejection. Even so, doing a side by side listening test reveals that it picks up more ambient room noise (I still think it is the furnace and radiator system in this house) than the SDC mics.

I've done a range of recording and live listening tests with my mics (not rigidly scientific but through headphones and with the mic level LED meters on my Duet and MacBook) and can say with some certainty that I live in a house that talks to LDC mics--or at least the ones I've used. To be more specific, it murmurs a steady love whisper in a relatively low voice (90-105 hz). It is plain as day when I just "listen" to the room through the mics and is consistent as I move around--high/low, near wall and in the center of the room. At comparable input levels and distance levels from sound sources, such as music coming through my Bose speakers, the KSM 137 is both more sensitive (about 10% more sensitive), flatter, and considerably quieter than the MK4. On live instrument recordings, by the time I do enough EQ and HiPass filtering to bring the ambient noise in the MK4 to a similar place as the KSM 137, I'm goofing too much with tone. So, goodby LDC mics because bigger is not better and this old house just loves you a bit too much for my recording sanity!

By the way, I'll post some pics of my new panel setup on Wednesday or Thursday, when my other panels arrive.

[ukejon]

Since my main issue is trying to create a quieter space within a larger room that otherwise has acceptable acoustics for solo instrumental recording, I've played around a little bit with using my panels to create a small, 3/4 closed enclosure. This "isolation chamber" is sort of an extension of Fran's idea about closing off the back side of mics with panels. If I sit in a relatively low chair, a large percentage of the ambient room noise (some of which is coming in from the large windows in the room) goes away. This, in combination with paired KSM 137 mics (no more large diaphragm mics....they hate this space!) gives me a relatively quiet room. I'll probably put a 2' x 2' x 4" panel right above where I play:

Any other ideas or panel configurations come to mind? Move away from walls?

[KevWind]

Yes one thought is , as far as the black panels. You could try placing them say 4 inches from the wall as opposed to right against the wall. Also you could try placing the panel nearest the corner at an equidistant 45 degree angle to the corner in stead of following the 90 degree angle of the wall. Also as far as the low level bass hum if you have an EQ with a Bass roll off or High Pass filter try setting it at say 110 hz. To 150 hz, There, is very little If any good usable low end info from guitar ( other than boom) below about 200 any way . And roll off ( or cut ) everthing below that and do it steeply.

[ukejon]

Also you could try placing the panel nearest the corner at an equidistant 45 degree angle to the corner in stead of following the 90 degree angle of the wall.

Do you mean the way bass traps typically are put into corners? If that is the case, I could take one of the 4' x 2' panels and put into the corner at this 45 degree angle and then work out from there. Thanks for the suggestion.

[Doug Young]

Originally Posted by KevWind

Yes one thought is , as far as the black panels. You could try placing them say 4 inches from the wall as opposed to right against the wall. Also you could try placing the panel nearest the corner at an equidistant 45 degree angle to the corner in stead of following the 90 degree angle of the wall. .

Those are good ideas for improving the efficiency of the acoustic absorption of a given panel, not sure it will help much with isolation from outside noises, tho. Acoustic room treatment and keeping noise out are very different issues.

The main thing that helps with getting rid of sound from outside your environment is isolation. Is your ambient noise coming from the room you're in (computer)? Or elsewhere? If it's coming from other rooms, try making sure all doors are shut and tightly sealed as much as possible. Close off the gap under the door with a rug. Close curtains on windows, cover heating vents. What real studios to do get rid of external noise can get pretty intense - a local studio I use even has the concrete foundations of each room isolated from each other so no sound travels thru the floor from one room to another. That's the kind of thing it takes for complete silence - floating floors, double walls, etc. I suspect you're not going there :-), so just do what you can to close off any air pathways between you and the noise.

[KevWind]

Originally Posted by ukejon

Do you mean the way bass traps typically are put into corners? If that is the case, I could take one of the 4' x 2' panels and put into the corner at this 45 degree angle and then work out from there. Thanks for the suggestion.

Yes exactly.That and the 2" to 4" gap between the walls and the absorbers (if possible) What that does is make the sound wave travel through the absorber which is one density then through the air gap which is a different density, hit the sheet rock then the reflection goes back through the air then through the absorber before going once again to the mic. I was told that increases the effectiveness of your absorbers. As Doug points out Ambient and Outside noise are additional issues.

[ukejon]

What I am discovering, with more experimentation to follow, is that tucking myself and the mics inside of this 3/4 closed "room" or isolation chamber greatly cuts down on unwanted external noise entering the mics. In other words, my "room treament" really has come down to the creation of a space within the space. Covering the large windows with a thick drape or upholstery blanket will undoubtedly will help as well. As for other noise sources, computer goes into the closet when recording and fortunately no air vents or returns...just noisy old Lake Michigan. Also, I've killed both cats and the dog.....just kidding. You might be interested to know that in this 1901 house, a timber frame "summer cottage", the floors were filled with sand, perhaps as a insulator or maybe to keep noise down.

Now I need to play around with the quality of the acoustic sound within this quieter space--floor and ceiling treatment, mic placement (x-y, ORTF, spaced, etc) and the like. Is it properly reflective? Roomy enough? Too dead? Lots to play around with. Thanks so much for the help....this thread and the generous contributions by readers has been a total game changer for me.

[david.guitar]

Have you tried treating the room with acoustical foam or other noise canceling treatment? Also, if you're trying to avoid picking up room noise, be sure that you're using unidirectional mics (that only pick up sound from exactly where you're pointing it. If I'm not mistaken, hypercardiods also pickup up sound from the back as well as the front. Placing the mic as close to the instrument as possible (while still achieving a good tone) should also help with this.