Measuring sound levels

Aruffell said:
So upon measuring a graphics card at idle and load from around 10cm away, i was given the following readings:
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Why did you decide to measure the sound at 10 cm away?

You may get better results at 1 metre away, as most SPL measurements are taken at 1 metre away.
 
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There's various sound level apps for smartphones out, this is what my office (just me in here) reads right now:

SC20110524-161327.jpg


If I move/whisper it climbs obviously.

Is that not reasonably accurate enough?
 
Khaaan! said:
There's various sound level apps for smartphones out, this is what my office (just me in here) reads right now:

SC20110524-161327.jpg


If I move/whisper it climbs obviously.

Is that not reasonably accurate enough?
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Phone mics will have interference/white noise/static that calibrated sound measuring equipment wont. I wouldn't trust a phone app reading at all.
 
thedoc46 said:
Looking forward to going deaf?
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Funnily enough I've played in front of bands for 41 years now with no impact on my ears however I am deaf in my right ear but not through loud music.
It's an hereditary condition that can be fixed by surgery but when noise reaches a certain level I have perfect stereo hearing.
If I put my hand over my left ear and you talk I wouldn't hear you.
 
krooton said:
Phone mics will have interference/white noise/static that calibrated sound measuring equipment wont. I wouldn't trust a phone app reading at all.
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Some phone mics have noise cancelling features (this one does) - According to the reference chart below the dial it seems to be accurate enough though which was why I asked. Looking on line at suggested reference levels, these seem inline as well.

Was just confused at some of the comments^ that's all!
 
Aruffell said:
Will give it a go, tried various distances away.
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Most speaker manufacturers quote sensitivity (dB\W) at 1 metre, so I can only assume 1 metre is the closest to a standard distance that it used for SPL measurements.

From wikipedia:
The distance of the measuring microphone from a sound source is often omitted when SPL measurements are quoted, making the data useless. In the case of ambient environmental measurements of "background" noise, distance need not be quoted as no single source is present, but when measuring the noise level of a specific piece of equipment the distance should always be stated. A distance of one metre (1 m) from the source is a frequently-used standard distance. Because of the effects of reflected noise within a closed room, the use of an anechoic chamber allows for sound to be comparable to measurements made in a free field environment.
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So I would stick with 1 metre and try to do it outside to prevent reflections also.
 
1 metre does tend to be a standard measuring distance, though your results may vary from a manufacturers measurement which is likely taken in an anechoic chamber; keep away from the walls, floors and any large surfaces as much as possible for accurate measurements.

Your difference between ambient and fan noise is greater than 10dB, which as a general rule means that the higher SPL level is taken as the actual level (this won't hold true if you have numerous smaller levels being added, but it is quite accurate in this case, in the case of the 55dB card noise and 20dB ambient, the actual level contributed from the card is 54.9986dB, immeasurably small difference!)

Bear said:
Yes with dBs you just add and subtract them, when you convert it into linear units you cant just add and subtract.
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Certainly not. If this were true, I could have a pair PA speakers running together and produce output greater than the eruption of mount Krakatoa!
 
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