Acoustic sealing a door. Seeking recommendations and a little science with db meter.

[JakeK]

The other thing that might be worth doing is a spectral analysis of the noise that is escaping. This does not need to be fancy. You can do this two ways: either compare the spectrum of noise inside the building and out, or do a sweep (REW can do this, or there's sweeps online) inside and out. The aim is to work out what frequencies are escaping. As a hint, bass is the hardest to stop: the only thing that stops it is mass, lots of. This is why you can often hear the disco down the road from some distance as thumps. If you generate white noise inside, outside it should fall off in roughly a straight line from bass to treble. If there are any bumps there is more sound leaking at that frequency (same applies to sweeps, should be a straight line falling off with frequency). Of course it never is, but you can get a clue to what the problem is from this. If there's bass lumps, tough, more mass needed. If middle, then there may be something resonating which can be damped. If high, it's a leak. This is very approximate of course. Good luck again.

I don't know how to do this. Can I do a useful spectral analysis with a phone?

 

[ElJaimito]

Best Audio Spectrum Analysis Apps for iOS and Android

13 audio spectrum analysis apps for Android and iOS devices.

www.channelpronetwork.com

This is not pro level, but that's not needed here. Using your chosen app, get the noise going inside the building - any noise will do, but for this I'd probably use white noise as it should give a roughly flat line on the display, but pink will do as well. Take a screenshot of the result for easy comparison. Then go outside and do the same thing. Compare. See what frequencies are standing out, that's where most noise is being conducted through the structure and door. To ensure unnoticed background noise isn't having an influence, do another external measurement without the noise generator on. Comparing them all, you should be able to see where there might be a problem. If nothing stands out then you're fine.

 

[JakeK]

Best Audio Spectrum Analysis Apps for iOS and Android

13 audio spectrum analysis apps for Android and iOS devices.

www.channelpronetwork.com

This is not pro level, but that's not needed here. Using your chosen app, get the noise going inside the building - any noise will do, but for this I'd probably use white noise as it should give a roughly flat line on the display, but pink will do as well. Take a screenshot of the result for easy comparison. Then go outside and do the same thing. Compare. See what frequencies are standing out, that's where most noise is being conducted through the structure and door. To ensure unnoticed background noise isn't having an influence, do another external measurement without the noise generator on. Comparing them all, you should be able to see where there might be a problem. If nothing stands out then you're fine.

The apps on that list were all really out of date and not on the play store but I found spectroid that looked useful. https://play.google.com/store/apps/details?id=org.intoorbit.spectrum

This is inside near to the white noise playing:



The yellow trace is the current reading and the red is the maximums. I only played it around 70db at this point as I don't think my phone can pick up anything over 80db Not sure if this mostly shows the limits of the mic in my phone or the response the speaker of I'm using. I imagine the phone mic is fairly limited.

This is the ambient noise outside for reference:



I turned up the noise a fair bit, closed the door and did readings from outside. This is outside the door with the door closed:



I don't know if that tells us anything useful. I can see it's highest around 200-300hz and drops off either side.

If this is of interest, this is outside the door with the door open and a very heavy curtain closed across the door. The curtain blocks/absorbs around 15db.



I hope these are of interest!