\"Measuring\" a room

Dra

Here's a good one.

I'm going with my brother-in-law to a church to bid adding dampening.
If I recall, it is something like 70 x 50 x 10. Tile floors, sheetrock everything else. He has contacts with a company that will spec what you need for whatever problem the room has. Anyway...

I suggested taking my 260 & RTA mic, along with either a pink noise cd or my Goldline box. Excite the room and take measurements all over the room.

Should I focus on wall, floor, and ceiling mesurements (at some specified distance (1/8\", 1/4\", 6\", etc)? Open air at head positions? Both? Something else?

What increments would you suggest (reading to reading)? Every 4'? 10'?

We will try to get a plot of the speaker (near field) to see what the room is doing. At this point we don't know if it is a reflection or resonant problem. Maybe both. Could be a crappy system, or all of the above.

Any way, Ideas?

Thanks,
DRA

Gadget

Well..I guess I would start with the same thing we tell everyone...find out what speaker pattern is used and evaluate if it's energy is being sprayed on the congregation or on the hard surfaces.. you know there is going to be no solution if the speakers have a 100 deg horn pattern and horizontal mounted speakers at the outside corners of the room...So first thing is to evaluate coverage and speaker position issues...It may be cheaper to propose a different speaker solution (like the frustration thread we have going now...) and then some possible treatment.

Use the Room mode calculator( see your email) to see what modes the room has, and at what points they will occur...

Ya I guess the 260 would help... but no substitute for an FFT...If the speakers ARE a good fit to the room, and they are deployed properly (Ya ... :roll: right) then perhaps try flattening the response as we have discussed and then see where you find yourself...A trip to the room during services... to see what happens when waterbags are added will be more revealing than a visit without, but the aforementioned issues should be evaluated and dealt with first...

Then armed with that data, a calculation of the room reverb length
http://www.marktaw.com/recording/Acoust ... ulato.html
and your ears and you should be able to start making some assertions.. If their is some standing waves and LF buildup some traps may be required to tame those.

Good luck
G

Dra

What am I seeing here (marktaw site).

I put in the room specs.

Under 125hz / 250hz / 500hz / 1000hz / 2000hz / 4000hz it gave a list of Sabine units x area of each surface, then at the bottom gave these undefined numbers (in order of the above freqs.
.86 / 2.22 / 3.92 / 4.62 / 3.00 / 2.56 with no label.

What is that? The time it take for a reflection to occur at fequency? For example 4Khz reflects every 2.56 sec? HUH? 2.56 msec?

What is this telling me? And how does it help me?

DRA

Gadget

It's important to know the reverb time of the room perhaps this:
http://www.csgnetwork.com/acousticreverbdelaycalc.html
Explains it better...

Remember that 2k is the critical vocal clarity value. If the 2kHz reverberation time values are greater than the target values shown below, you will likely have a speech intelligibility problem. These are the 2kHz target values for reverberation time for each of these applications.

* Classroom for hearing impaired accessibility 0.5 seconds
* Church or theatre for speech/amplified music 1.0 seconds
* Church or theatre for traditional music 1.5 - 1.8 seconds
* Meeting Rooms 0.6 - 0.8 seconds
* Large Convention facility 1.5 seconds
* Gymnasium for teaching 1.5 - 1.8 seconds
* Industrial Buildings 2.0 - 2.5 seconds
* Small arena (500 -2000 seats) 2.0 seconds
* Large arena (2000+ seats) 2.75 seconds

Check out this primer:
http://www.marktaw.com/print/recording/ ... 1-Mod.html
and this:
http://www.marktaw.com/print/recording/ ... 2-Ref.html

This will prime you for your task... check out the various reverb times...
http://www.bkl.ca/page131.htm

And finally this:
http://www.kettering.edu/~drussell/GMI- ... everb.html

Let me know if that helps
G

Dra

Thanks, that 1st link is much better and comes with an explanation. In my example above, in a give room size with given surface materials it takes 4khz 2.56 sec to be \"absorbed\" by the room to a point -60db of the original sound. In other words, how many times (at the speed of sound) will a frequency bounce off walls, ceiling, & floor until it is \"absorbed\".
More reading ahead.

Gadget is the bomb.

DRA

Gadget

:oops: Who me?