1/2" vs 1/4" tempered glass - how big of a STC difference?

[Firefox]

1/2" tempered vs 1/4" tempered glass - how big of a STC difference?



i'll have 2 sliding doors to keep the sound in and out of a new studio....

inner one is Fleetwood 3000 series - double glazed (1/4" glass tempered, 1/2" air, then 1/4" glass tempered)

the outer sliding door was gonna be 1/4" tempered single glazed, (Fleetwood 3000) but for about an extra $300 i think, i can make it 1/2" tempered. should I?

I'm told that it is good to keep nearby panes of glass different thickness, if possible.... to improve sound blocking.


thanks

[avare]

Definitely. When the two wythes of glass are the same thickness and type, the Transmission Loss (TL) has a dip at the same frequency referred to as the coincidence frequency. While this affects the STC of the window, it occurs at at such a high frequency, that for music isolation it is not important. However, the increased mass of the second wythe reduces the MAM frequency of reduced TL and increases the overall TL.

Andre

[Firefox]

Originally Posted by avare

Definitely. When the two wythes of glass are the same thickness and type, the Transmission Loss (TL) has a dip at the same frequency referred to as the coincidence frequency. While this affects the STC of the window, it occurs at at such a high frequency, that for music isolation it is not important. However, the increased mass of the second wythe reduces the MAM frequency of reduced TL and increases the overall TL.

Andre

Heya Andre

thanks for the info

can you explain what MAM and TL are? and how they relate?

Thanks

[avare]

Originally Posted by Firefox

Heya Andre

thanks for the info

You are welcome.

can you explain what MAM and TL are? and how they relate?

Ouch. It can a very complex subject to answer completely. TL is Transmission Loss. This is how much a barrier reduces a sound level in a given frequency band.

MAM is short for Mass-Air-Mass. It is somewhat unique to building acoustics in that the more proper acronym is MSM, which stands for Mass-Spring-Mass. In building acoustics the spring is almost always air, so MAM is used. Where the MAM resonance occurs, the TL (starting to tie it together) is lower.

With music, the biggest issue is low frequency isolation. The MAM frequency is usually in that range. Therefore it is of the greatest concern design wise.

To try and give an example of how these result in real life conditions, I have attached a drawing from NRC IR-761. The specific example is for a drywall wall, but the underlying physics are the same for windows.

The reduction in TL in the 125 and 160 Hz range is the MAM of the wall system. Not mentioned in this thread, the dip in TL at the 3 kHz region is the coincidence effect of frequency and bending frequency of the layer resonances. If a barrier is built to effectively reduce low frequencies, this dip is not important. This dip does affect the STC rating of the barrier though.

I hope this helps.

Andre

[avare]

Sorry, I forgot attach the attachment. Here it is.

Andre

[Weasel9992]

Brilliant explanation Andre...thanks for the chart too.

Frank

[Firefox]

so.... if i can swing the extra $... it would be good to have the outer door as 1/2" glass.....?



and - what about the whole 'triple leaf' scenario?

i'll have 1/4" glass, 1/2" airspace 1/4" glass in the double glazed inner door.... then a few inches gap (maybe 5 or 6 inches) then the outer door.... (single glazed, 1/4" or 1/2")

what do people think about that?

thanks

[avare]

Originally Posted by Firefox

so.... if i can swing the extra $... it would be good to have the outer door as 1/2" glass.....?

If cost is the issue, can you afford to do it wrong?

Regarding triple leaf, see above sentence.

Andre

[Firefox]

Originally Posted by avare

If cost is the issue, can you afford to do it wrong?

Regarding triple leaf, see above sentence.

Andre

I understand what you mean about not doing it wrong....

however - can you be more clear about your thoughts on 'triple leaf' ?

and - does anyone else wanna comment about triple leaf?

[avare]

Originally Posted by Firefox

can you be more clear about your thoughts on 'triple leaf' ?

You will have a triple leaf, which is bad for isolation.

Andre

[nosebleedaudio]

For high isolation use double wall, big air space, several layers of material.
The bigger the air space the better, 10 to 14".
The triple leaf reduces the air space...

[Firefox]

Originally Posted by Firefox

1/2" tempered vs 1/4" tempered glass - how big of a STC difference?



i'll have 2 sliding doors to keep the sound in and out of a new studio....

inner one is Fleetwood 3000 series - double glazed (1/4" glass tempered, 1/2" air, then 1/4" glass tempered)

the outer sliding door was gonna be 1/4" tempered single glazed, (Fleetwood 3000) but for about an extra $300 i think, i can make it 1/2" tempered. should I?

I'm told that it is good to keep nearby panes of glass different thickness, if possible.... to improve sound blocking.


thanks

it turns out that to upgrade the outer sliding door from 1/4" tempered single glazed to 1/2" tempered single glazed - it is an extra $750/door - so an extra $1,500.... ouch.

is it worth it?

[avare]

Originally Posted by Firefox

it turns out that to upgrade the outer sliding door from 1/4" tempered single glazed to 1/2" tempered single glazed - it is an extra $750/door - so an extra $1,500.

Yes, I would do it. However, I would also get a quote for 1/2" laminated. If temoered is required by building code in your area, 1/2" laminated made from 1/4"tempered. It is a custom order, but might be cheaper than 1/2" laminated, depending on how the price structure is set up at the suppliers.

Andre