Hi!
Patrik T wrote on Sat, 04 September 2010 17:27 |
Hi I'll run a few more sweeps when time allows. The reason I posted the first plot was how surprisingly even it looked. I've just been moving things around by ear before.
|
Try recording something normal, like yourself, to check that everything's alright. Make some impulsive sound to check transient response. Talk both in front and behind the mic to check omni response. Whistle to hear if there's aliasing. The sine sweep will sound weird if there's something very wrong on the output side. Have had occasions where there was alias distortion from non-SRC'ing sound cards at wrong samplerate. Sounds like a flying saucer attack.
Should be a pure tone.
The graphs show a very loud measurement level and/or very low noise floor. Is that right? Do you have an SPL reading for the measurement?
(apologies if this is all way too obvious! better too much than too little..)
bruno putzeys wrote on Sat, 04 September 2010 17:59 |
Having written my own measurement program from scratch I can tell you it's remarkably difficult to make a sweep-based (a la Farina) method that has no pre-ringing. I cracked it but it wasn't obvious. So you're quite likely to see something like this in a sweep based test whereas it wouldn't appear in an MLS based one.
|
Wow! Cool stuff. Know what you mean. The sinesweep->impulse way isn't particularly clean as usually implemented. Cudos for "cracking it" (however you did it!).
50ms is a _lot_ of preringing though. Had a look a couple of different room measurements I had at hand and most of them rise from noisefloor some hundreds of microseconds ahead, to some milliseconds. One measurement was out of normal at 7 milliseconds. Nothing like the steady climb from 50ms in these graphs.
Regards,
Andreas Nordenstam