What is Your Signal to Room Noise?

[STC]

2 hours ago, PeterSt said:

Over there the ambient noise was 4dB less than over here. This is how my mentioned 4dB came about in my first post.

So because the ambient noise was 4dB less there, the hum which surely was there, deep down, became audible (became profound) . The hum was now measurable just because the base level was 4dB less. I couldn't believe it.

 

I also couldn’t believe it.  Let’s say the hum is 33dB at 1meter away and the noise floor is 30dB. So let’s say, you hear 3dB over the NF at 1 meter. This is a very generous value given that you said it is only heard by a few at ear in speaker distance. 

 

In your customer’s room the NF is lower by 4dB. So let’s say it was 26dB. 

 

The noise must be above 26dB at the listeners position to be audible by him. The conservative value of 2 meter would have attenuated the noise by 6dB so at LP it is barely 1dB above the NF.  

 

In reality, the noise level is much lower and only audible at ear in speaker. Could there be other factors that you might have had overlooked?

 

[STC]

9 hours ago, PeterSt said:

Next is that the noise floor over there is 4dB lower and thus is at 35dBSPL (you are already at 26 there).

 

Pick any values you want. You have 6dB loss for every doubling of the distance. Not every 1 meter. 

 

 

[STC]

2 hours ago, PeterSt said:

 

Oops, I surely wrote that wrongly. Thanks for the correction. But point is, it is not about that (hence the easy mistake - blurp). It is about the directivity and how that makes the rule fail. Try a tube ... (of 100m long if you want).

 

Be it line array or waveguide horn, the best it could do is 3dB attenuation. So at 7 meter and a 4dB lower NF, it cannot be the reason as you suggested in the earlier post. 

 

It is possible the system at your customer’s place could be picking other noise that get amplified. 

 

I have nothing further to add. 

[STC]

1 hour ago, PeterSt said:

 

Nobody said that was at 7m at the customer.

 

My mistake. I was guessing since you are not giving the distance. 

 

 

1 hour ago, PeterSt said:

 

 

Then try that tube. Don't you believe that or what ?

 

 

I have two eight feet tubes to do such experiment. None of the sounded like a good horn speaker when heard in the other end of the tube.   

[STC]

Classical and vocal. Peak hitting 102dB for classical. Lowest room level without air conditioning 29.2dB with both A and C weighting. 

 

 

 

 

[STC]

21 hours ago, daverich4 said:

 

Can I ask you what app this is? Is it for Android? I can’t find it in the Apple App Store. 

Toolbox - Smart Meter Tools by SkyPaw Co. Ltd
https://itunes.apple.com/my/app/toolbox-smart-meter-tools/id933528345?mt=8

 

I have Pro’s Kit and also used Castle DPL Meter which is about $1500. None of them could go below 29dB. 

 

In my room, the sound without air conditioner is at 29 to 30dB and with air cond also around 30dB. With Pro kit it was 32 or 36dB with pc and air cond. if I remember correctly only Castle was sensitive enough to give different reading for all. 

 

The iphone app is good enough although accuracy is not captured below 30dB. I believe my room is at low 20dBs but without a proper SPL meter it is anybody’s guess.