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Old 27th October 2013, 02:28 AM   #21
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Analyzer is seeing white noise when it is looking for pink.

What were settings?
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Old 27th October 2013, 06:38 AM   #22
jayadev is offline jayadev  India
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Barelywater,

I did not get you,there was no inputs given.if line or mic was turned on, the graph would raise 10-20db more.

May you can be more specific,because Trta has got not much of settings.REW I am not very sure yet.

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Old 31st October 2013, 02:13 AM   #23
Eldam is offline Eldam  France
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Quote:
Originally Posted by Barleywater View Post
Impulse response measurement with swept sine is much better way to measure, be it gear, speakers, or room interaction.



Generic measurement microphones are typically very flat from 50Hz-4kHz, some up to about 7kHz. High quality measurement microphones are often flat from below 10Hz to >20kHz.

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Hi Barelywater,

I found a swept sine wav file at audiocheck.net. Here is my measurement with peak holding.

Without signal in silent room below 2Khz the curve is klimbing from 15 DB up and down ! But flat above 2 khz within 2 db with smoothing on.

is the + 2 or 3 db at 4khz can give a brighty treble or peak energy in treble ?

Why below 2 khz without sound the curve is not flater ? Hope to be in topic.

Pink Noise give a diferent result with peaks at 3300, 4500, 6 to 7000 hz
Attached Images
File Type: jpg sweep sine wth peak hold in home room.jpg (64.3 KB, 155 views)

Last edited by Eldam; 31st October 2013 at 02:17 AM.
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Old 3rd November 2013, 09:00 PM   #24
Eldam is offline Eldam  France
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Hi Jayadev,

did you suceed having a flater response in your room (without sound) ?
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Old 4th November 2013, 06:36 AM   #25
jayadev is offline jayadev  India
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Quote:
Originally Posted by Eldam View Post
Hi Jayadev,

did you suceed having a flater response in your room (without sound) ?
Hi Eldam,I'm away from home right now,couldn't continue.I will start over by this weekend.
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Old 5th November 2013, 10:20 AM   #26
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I don't see a problem here. This s/w is measuring the level in fractional octave bands, so if your residual soundcard noise is essentially 'white', then you would expect the plot of the noise to rise at 3dB per octave. At a first glance, this appears to be what you get.

This is the reason why you use a pink noise signal for fractional-octave RTA measurements. (Pink noise rolls off at -3dB per octave, so produces a flat response curve when measured by an RTA). If your plot was measuring the noise in bands of equal Hertz (perhaps in 1kHz wide bands) then you would see a flat measurement result if the noise is white.
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Old 5th November 2013, 12:16 PM   #27
Eldam is offline Eldam  France
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OUROBOROS, thank you for your input...

Don't want to high jack the post of Jayadev. Sorry for my low knowledge, but does it mean that I don't have to be frighten by big variation of the curve in a silent room when my mic and RTA are switched on ?

Because the low end of the mic+room are always enough flat (I have peak of more 10 or 15 db below 1,5 khz in silent room) for sweep sine or pink noise injected ?

Is it another way to say that with pink noise injected with a good enough micro (here ECM8000), I will see only the trouble of room+speaker in bass area and not the relation between mic+soundcard+phantom powersupply added to the measurement of the speaker ?

Last edited by Eldam; 5th November 2013 at 12:19 PM.
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Old 5th November 2013, 02:57 PM   #28
sangram is offline sangram  India
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Given a muted input, the absolute noise floor is below -100dB, slope being irrelevant at such low levels. This is a 'good' result. If you have -80dB noise floor with mic turned on and gain set correctly (0dB input to output, 60dB at mic producing 60dB at loudspeaker) that would be classified as 'Excellent'. It is practically impossible to have actual noise floor below -60dB in most urban settings. I don't know where you live, but most cities in India are frightfully noisy at all times of the day. In a very quiet, untreated room in the middle of the night, I get about -50dB when the microphone is set to 'medium' sensitivity. Real noise floor is closer to -40, treatment can improve this handily but I haven't got around to doing it.

The USB Creative soundcards have a peculiar problem that you will encounter when actually using for measurement, seek out the Asawari build thread to find it. You will never get the response aligned correctly because of the variable latency over USB using the Creative drivers.

You can surmount this by using a low-latency solution - either a PCI/PCI/Express soundcard (and not creative, something with decent drivers) or a good USB solution that offers ASIO drivers. You will still have round trip latency of 10mS or so, but you can adjust that in RMAA because it's more or less fixed.
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Old 7th November 2013, 04:28 PM   #29
Eldam is offline Eldam  France
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Very helpfull, thank you.

At night it depends in france, where you live and the moment of the night and if you are in a modern construction (Three or two layers of windows).

After 2 am , i have a relative quiet room, and can find ten second for inject a sweep sine.

I will have a particular look to the DB column.

My Creative pre usb use ASIO drivers...

Last edited by Eldam; 7th November 2013 at 04:35 PM.
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Old 12th November 2013, 11:05 PM   #30
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Quote:
Originally Posted by sangram View Post
In a very quiet, untreated room in the middle of the night, I get about -50dB when the microphone is set to 'medium' sensitivity. Real noise floor is closer to -40, treatment can improve this handily but I haven't got around to doing it.
Agree, I didn't use mic based RTA so far, rather I recently started using android phone based RTA apps.

One easier app I am mostly using is -RTA Audio Analyzer

It reads around -50db when nothing is playing in my room. The curve with default setting is also not flat. Here the noise of computer, inverter etc are also accounted. I chose standard calibration before measuring the audio output. Standard calibration brings the most of low, mid and high frequencies at level except few raised bars here and there.

When I try to measure pinknoise, I let the volume raise until it reaches upto till -20db peak approx. Then I try to make the curve of pinknoise output flat using param EQ in JRiver. The sound changes drastically. Am I doing it right?

Last edited by Jack Sparrow; 12th November 2013 at 11:07 PM.
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