Episode #25 - Acoustic Doors Don’t Work Alone: What Really Impacts Performance

Part 2 in our acoustic door series continues the conversation between Grace Jacob of IAC Acoustics and Mike Sirna of Hensel Diversified Construction, digging deeper into something that surprises a lot of people: the door itself is only part of the acoustic performance equation.

Whether you’re an architect writing specs or a contractor installing in the field, this episode offers practical insight into how your door selection can directly impact performance, reliability, and project outcomes.

To learn more about IAC's acoustic doors, visit: IAC Acoustic Doors

 

Part 2 of our Acoustic Door Series

Acoustic Doors Don’t Work Alone: What Really Impacts Performance

Lisa Morrow

Welcome back to the podcast. In our last episode, we compared factory installed acoustic doors versus kit acoustic doors and talked about how those approaches affect performance and installation. Today, we're continuing the conversation and digging into something that surprises a lot of people: the door itself is only part of the acoustic performance equation.

I'm joined again by Grace Jacob, IAC Acoustics Architectural Doors and Windows Sales Manager, and Mike Sirna of Hensel Diversified Construction, who installs these systems in the field.

Grace, let's have you kick things off. When someone purchases an acoustic door, what kind of performance are they typically expecting? And are there any misunderstandings that ever come up in those discussions?

Grace Jacob

End users sometimes are looking for what they call something soundproof. Unfortunately, soundproof doesn't exist. What's important is to set the expectations that sound will be reduced but not gone entirely.

Let's say they have an STC-55 door specified and they're expecting an STC-55 performance in the field. What they're really looking for and what they're really gonna get is this thing we call NIC, and that's the field test equivalent. Because in a lab, to get STC performance, all the conditions are perfect. But on any construction site, you have absolutely no control, right?

So typically, you'll have up to a five-point difference for NIC versus the specified STC. Now again, sound's not going to be gone, but it will be reduced, and that's kind of the industry standard.

Something else is, it depends on what the noise source type is. Some STCs are going to do really great at blocking the sound of speech, but it's going to be different if it's a drum kit on the other side of that door or music. It all kind of comes down to the frequency and the actual loudness of any source type.

So making sure that you're working with an acoustical consultant that knows what to look for in the STC reports and is matching up the frequencies that you're concerned about versus the frequencies that are actually being blocked with any particular product.

Lisa Morrow

Thanks, Grace. I think you teed that up nicely for Mike. I'd like to jump in and talk a little bit about the bigger picture. What are some of the factors beyond the door itself that can impact acoustic performance?

Mike Sirna

I've always been a fan of the environment where the door is being plugged in is key. We've done stuff where you could have an industrial complex. We did a project for Disney years ago where everything was perfect, but on Tuesdays between 10 and 11, there was some giant industrial punch press working and the low frequency reverb destroyed all the stuff that we did.

Any other time in the day? Perfect. Tuesdays between 10 and 11 — he basically darkened his studio for that.

So I say that environment is key to high performance. If you have the optimum environment, the door is going to perform perfectly. If there are environmental issues like freeway traffic, big truck traffic, or cars honking their horns incessantly, this is all going to be pressures that are going to possibly affect your performance.

Lisa Morrow

And from the installation side, Mike, are there any things you see in the field that can affect how well the door performs?

Mike Sirna

I think in the last podcast, we talked about the importance of making sure that the opening that the door is going to be plugged into is — I say it's a three-axis performance. You have plumb vertical and true.

The way I describe it is we use a laser and we look at the edge of the jamb. Is it perfect? Yes. We look at the horizontal top of the header. Is it perfect? Yes. And then you stand in the doorway and you look at the side of the jamb — is that perfect?

If it's tilted in or out, that's going to affect the door because these doors, when they're tested, are nice and tight and put in an opening that's perfect.

So to get that performance, we need that kind of opening. And it's a challenge in the field because you have people framing openings and installing drywall who aren't approaching it from the standpoint of someone like myself who comes in and says, this has got to be pristine.

It is critical that the floor is level. It's critical that the framing is plumb and true. Most of the time, it's a challenge in the field.

Lisa Morrow

Thank you. Now I'd like to hear from the both of you. What are some of the smaller details people might not think about that make a big difference? Grace, why don't we start with you?

Grace Jacob

Something I like to emphasize the importance of that usually gets overlooked is the sill plate or the threshold.

The reason that we encourage a sill plate on every project is because it is going to be a smooth, continuous, flat, reliable place for the bottom seal to have complete and continuous contact.

Sound is like water, and so it will find any small spot to leak through.

Sometimes for aesthetics, I have an architect that does not want a sill plate. They like the tile they've chosen, but they're not recognizing it has grouting paths that will allow sound through, or they're putting these on top of carpet and don't realize that's going to let a ton of sound through.

Just because carpet absorbs some sound doesn't mean it's going to block it.

Those little flanking paths are difficult to mitigate without a threshold. Once the frame and sill plate are aligned, the leaf is then hung and the bottom seal is dropped to make complete and continuous contact with the threshold.

Then from there, the frame and sill plate should both be caulked in place to make sure there are no extra flanking paths.

If you remember, I said NIC can typically have up to five points difference, but it doesn't always have to be a full five.

Lisa Morrow

And Mike, from your experience installing these systems, what are details that can make or break performance?

Mike Sirna

Touching on what Grace said about flanking paths, I've got a great story about a job we did.

They had built these engine Dyno-Cells with CMU cinderblock walls and installed acoustic doors and windows. Everything tested perfectly.

Two months later, I got a call from the contractor in full panic mode saying the doors and windows were failing.

I came out to test the room and noticed a light switch box mounted on the wall. When they removed the plate, there was a three-quarter-inch conduit penetrating through the wall that had never been sealed.

That was the flanking path.

They later audited all penetrations, sealed the conduits, and the performance returned to perfect.

Flanking paths are always the Achilles’ heel. We can install the doors perfectly, but if additional conduits, lighting controls, or penetrations are added later and left unsealed, performance suffers.

Most people don't think in terms of noise isolation, and nine out of ten times, that's the problem.

Lisa Morrow

I think that's a good takeaway. To wrap things up, if there's one thing listeners should remember when thinking about acoustic door performance, what would it be? Mike, why don't you start and then Grace, you can take us home.

Mike Sirna

Acoustic door performance is all about the environment. If the environment is perfect, your door is going to perform like a star.

If you have anything challenging that performance and you don't take proactive measures to address it, then your door is not going to perform.

Grace Jacob

For me, I'd say that soundproof doesn't exist, and the frequency of the noise source will affect the performance of whatever you choose.

And to everyone else, I'd say: use the sill plate, please.

Mike, I think you have a story about a time you didn't use a sill plate, but the conditions were correct. Could you mention that?

Mike Sirna

We did a project in Florida for a mixed VR company that had an STC-55 door. When we were setting the sill plate, the end user asked what it was for.

He explained he didn’t want carts bumping over the sill because they were moving sensitive equipment.

The floor condition, however, was high-polished concrete that was completely level and perfect.

They signed an acknowledgment that performance couldn't be guaranteed without the sill plate, but when the door was tested, it performed exactly as if it had one.

That was the exception to the rule, but I agree with Grace — using the sill plate is the best way to go.

Lisa Morrow

Great insights from both of you.

In the next episode, we're going to shift gears and talk about common acoustic door installation challenges and lessons from the field, including some of the mistakes that can impact performance.

Thanks for joining us, and we'll see you next time.