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Measuring a space for frequency response & isolation.
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Author:  MrSoundGuy [ Sat Oct 19, 2019 2:10 pm ]
Post subject:  Measuring a space for frequency response & isolation.

Hi All,

I’ve been asked to measure a friends shipping container recording studio for frequency response and isolation. I was wondering if anyone would like to weigh in with advice on the method I’m planning to use?

The equipment that I have is an Earthworks M30 microphone and an audio interface and the speakers which are in the studio which are Event Opal’s. I’m using Fuzz Measure software on a MacBook Pro.

The studio is built with soffit mounted positions for the speakers. The position for the mixing console/control surface is also fixed so the mix position is defined.

I plan to set up the microphone at mix position and run sweeps over 10 seconds from the single speaker left, single speaker right, then left and right combined. There is also a listening position for guests at the rear of the room. I’ll take further measurements at this position using the same L, R, L&R combo. Does this sound sufficient & workable? Will this provide usable results. Would I need to take a speaker out and put it on a stand & try reversing everything to get more complete results or would the single end method be sufficient?

For the isolation measurements I was planning on moving the speaker onto a stand inside the space and placing it 1m from the boundary facing the boundary. ie the wall.
Then placing the mic outside 1m from the boundary and measuring with sweeps and pink noise. Do this for all boundaries & averaging the results. To seal the studio i will need to have a separate device to generate sweeps & pink noise in the room, i will use another laptop to do this. Does this sound like it will give usable results? Should i reverse this process & generate outside & measure inside or would the same results occur? (Obviously there would be less ambient sound to effect results)

Would anyone like to offer a better solution with the equipment I have? Or any general advice?

Any help would be greatly appreciated!
Thanks in advance.

Author:  Gregwor [ Sun Nov 24, 2019 8:07 am ]
Post subject:  Re: Measuring a space for frequency response & isolation.

Sorry for the late reply, but here is everything you need to know:

viewtopic.php?f=3&t=21122

Also, REW's manual covers most of the topics in terms of understanding the measurement results.

Greg

Author:  DanDan [ Tue Nov 26, 2019 1:54 am ]
Post subject:  Re: Measuring a space for frequency response & isolation.

For Isolation and Modal investigation you can use a powerful mobile speaker. Quality is important within reason. A small modern bin and top PA, Mono, be fine.
To see all the modes well, place the speaker in a tri corner, i.e. floor corner. If you have two subs, two opposing corners.
Place the mic in the opposite tricorner. Ceiling corner, close to the surface, PZM style. If you have time and energy do the other corners also. This will light up all the modes strongly. For listening accuracy and possible Target Curve generation, you seem to have all that in order. One point, I would test a listening zone. Albeit quite small, say 1.5M x 1M. We do move about, but even at a fixed optimum spot neither of the two ears is at your nose! If you stand sometimes, measure that too.

Isolation..... there are well defined, to a legal level, standards. Is that your purpose? i.e. Legally defined for planning/neighbour reasons? Or do you just want to assess in terms that a regular audio engineer will understand? In either case best to have an Integrating SPL Meter. For assessment there are iPhone Meters. Here's a fine free one. https://www.cdc.gov/niosh/topics/noise/app.html Calibration and such is not important as you are measuring differences not absolutes. Integrating Meters measure a 'dose' over say 3 Minutes. Sorta like the LUFS we are now adopting in Mastering. https://www.bksv.com/media/doc/br0047.pdf
For legal purposes the instruments are megabuck and certified, and have to be operated by a qualified operator.
You have obviously read some of the methodology, but don't forget to try different locations quickly. Move abut, listen. Look for trouble, traffic, trains, planes. Windows and doors, ventilation.... Leaks.
In and out is totally symmetrical but there will probably be a higher background level outside. This can determine if leakage is a problem or not.

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