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Measurement using handheld decibel meter

Matias

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#1
I am new to measuring room acoustics. I have a decibel meter like the one shown below, and tested it holding on my hands while the system reproduced 5 second sine waves on the bass range (1 Hz increments from 22 to 65Hz). I wrote down the results and plotted below.

I noticed I should discard <31Hz as the meter is not specified to work on that range.

Question is: how accurate is this? Good enough or rubbish? Any suggestions on how to improve such a crude way of measuring (without USB mic and REW, etc)?

Thanks. :)

41XBSFNFmNL._SX425_.jpg


Specifications

• Measures from 30dBA to 130dBA
• Accuracy of +/- 1.5dB
• Resolution to 0.1 dB
• Frequency weighting: A
• Sampling rate of 2x/second
• Frequency response: 31.5Hz ~ 8KHz


graph.JPG
 

Krunok

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#3
I am new to measuring room acoustics. I have a decibel meter like the one shown below, and tested it holding on my hands while the system reproduced 5 second sine waves on the bass range (1 Hz increments from 22 to 65Hz). I wrote down the results and plotted below.

I noticed I should discard <31Hz as the meter is not specified to work on that range.

Question is: how accurate is this? Good enough or rubbish? Any suggestions on how to improve such a crude way of measuring (without USB mic and REW, etc)?

Thanks. :)

View attachment 33241

Specifications

• Measures from 30dBA to 130dBA
• Accuracy of +/- 1.5dB
• Resolution to 0.1 dB
• Frequency weighting: A
• Sampling rate of 2x/second
• Frequency response: 31.5Hz ~ 8KHz


View attachment 33242
That device is good for measuring absolute sound pressure levels. What you need to measure with REW is a calibrated measurement mic (I recommend miniDSP UMIK-1). You can then calibrate it within REW to show accurate absolute levels with your device.
 

Matias

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#4
The A-weighting will severely under-represenent the lower frequencies:



I would prefer a meter that supports C-weighting.
Good info, thanks a lot.
So based on the yellow A-weighted curve, the roll off on my graph is more mic based than actual SPL.

What is actually useable on my graph is the relative amount, that is, that large -10dB dip on 52 Hz, I presume?
 

digitalfrost

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#5
What is actually useable on my graph is the relative amount, that is, that large -10dB dip on 52 Hz, I presume?
More or less, yes. While it's still skewed by the curve, the relative could be somewhat usable.

That said, filling a dip if often not a good idea - try it. You could be pumping a lot of energy into your speakers without changing much acoustically. If your speakers are bass-reflex, be sure not to boost below the tuning frequency.

I agree with Krunok, it would be best if you got a measurement mic. If you calibrate that to a certain SPL is irrelevant as long as you don't care about absolute levels. But you could use your SPL meter and pink noise to get a good calibration, even with A weighting.
 
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#6
You might also want to make some sort of rig to put it on a tripod and not hold it your hand. At least that's what I've been told. I use an old analog sound level meter that i got from Radio Shack, but which is still available from other retailers.. and I set it at 90dB "slow" and "C' to adjust for level only. That's not what you're doing, but it's relevant because until I placed it on a tripod I didn't get accurate readings.

 

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