Truths about booths #1: Soundproofing

What’s the real difference between a €3,000 booth and an €8,000 booth?

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What’s the real difference between a €3.000 booth and an €8.000 soundproof booth? What features should you demand? What red flags should you avoid?

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If you are looking to invest in soundproofbooths or office pods, this series of blog posts was written for you.

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Over four posts, we’ll explain different aspects of booths in simple to understand language, covering all the keyaspects from soundproofing and ventilation to comfort and durability.

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We’ll show you how booths are built, how different manufacturers make different engineering decisions. We’ll even tell you how some manufacturers cut corners to save money. And then we’ll show you how to spot it before you part with your own money.

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At Persy Booths, we make booths. It’s in our name. But we’re not telling you which booths to buy. We’re just giving you the information so you can make that call for yourself.

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Ready for the facts? Let’s lift the lid.

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This is blog 1 in the series. You can also explore:

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• Blog 2: Ventilation
• Blog 3: Comfort
• Blog 4: Durability, warranty and support

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The truth about soundproofing

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Soundproofing. The reason you’re buying the booth in the first place, to isolate sounds and provide a quiet space for your teams. But don’t forget that soundproofing stops sound travelling in two directions.

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Huh?

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If sound travels into a soundproof phone booth, it’s noisy. It’s hard to concentrate. You can’t hear the person you called.

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But if sound travels the other way, people outside can hear what you’re saying. In a busy office, soundproofing can be just as much about privacy and confidentiality as it is about concentration.

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So with that double benefit just waiting to be grabbed, let’s get into the topic of soundproofing. Here’s a quick summary:

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• Soundproofing works both ways – it improves focus and protects privacy
• It depends on three things: walls, joints, and sealing
• Thicker, heavier booths with more layers perform better
• Weak points are usually joints, doors, and ventilation
• Around 28–30dB is sufficient for most office environments
• ISO ratings help, but real-world performance matters more

The three factors that affect soundproofing

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There are many ways to approach soundproofing. In short, it breaks down into three factors:

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Wall construction and materials

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• How the parts come together – making it difficult for sound to travel via joints
• Preventing sound travelling via ventilation channels and door seals

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If you understand these three issues, you’re well on the way to understanding what makes a well-soundproofed booth. And deciding whether the one you’ve been looking at justifies its price tag.

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1. Wall construction and materials

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It’s pretty simple – the thicker the wall construction, the more materials and layers can fit inside. The more material sit can fit inside, the better it works because different materials reflect and absorb different sound frequencies.

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The cheapest booths will have only two or three different materials. One of those materials has to be something solid like MDF or aluminium to provide structure. Inside the booth there is usually a felt layer to absorb echoes inside the booth (although felt itself doesn’t provide good acoustic blocking capabilities). If the manufacturer uses 3 layers, that leaves a single layer for the actual absorption and cheap booths typically use the cheapest material in the market.

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It’s all about the layers

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For better soundproofing, you need at least four layers, ideally five. In addition to the echo-reducing felt or soft fabricon the inside, the construction should include layers of different materials: some soft materials like wool, some medium like acoustic boards, some hard like MDF or aluminium sheets, thus blocking a range of sound frequencies.

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Higher-quality booths therefore have thicker walls and are typically heavier. A well-built single-person booth should have walls of 7–8cm thickness and be around 300–330kg. As a rule of thumb: if it weighs 200–250kg, it’s likely that shortcuts have been taken and the soundproofing performance will be affected.

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Apart from walls, pretty much all booths have at least one glass side. If you really care about soundproofing, ideally you’d look for booths with vacuum-sealed double glazing (sound doesn’t travel well if there are no air molecules) but this is an expensive solution that significantly inflates the price of the booth. For most offices, good quality, double-glazed, acoustic-grade glass will be fine.

What to look for:

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• Wall thickness of 7cm+ (can be 1–2cm thinner if aluminium sheets are used instead of MDF)
• At least four layers of materials
• Acoustic-grade double glazing glass
• Sturdy construction (a single person booth should weigh 300kg+)

What to avoid:

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• Wall thickness of <7cm
• Three or fewer layers in the walls
• Plexiglass, single-layer glass or tempered glass
• Booths weighing 200–250kg per single person booth

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2. How the parts come together – making it difficult for sound to travel via joints

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If a manufacturer has a decently soundproofwall, they’ve made a great start. But how do they put the walls together, ensuring that the sound doesn’t travel freely between the gaps? Every connecting point is a channel that sound can travel through, whether betweenwall and door, wall and base, wall and roof, and so on. But soundproofing engineers solve the problem by making the joints more complex, with multiple angles that break up the sound. These sophisticated joins are more expensive to build but can drastically improve soundproofing.

Version 1: Cheap to manufacture but, without perfect installation (which is unlikely), there is a direct channel for sound. In cheap booths you can sometimes even see through the join!

Version 2: These joints may appear to be more effective since the visible gap is sealed off by the felt layer. But don’t forget that the felt is there to reduce echoes, not to block sound – so soundis still free to pass through it.

Version 3: This is what you’re looking for. The solid soundproofing material is joined in a way that creates angles and thus breaks sound waves. Higher-performance booths use this technique.

What to look for:

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Joint systems that break the sound waves, making it difficult for sound to travel directly into and out of the booth

What to avoid:

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Simple constructions that lets the sound travel in and out of the booth directly. If you see daylight through the gap, walk away!

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3. Preventing sound travelling via ventilation channels and door seals

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Sound is persistent. So even if you have double-glazed windows and high-quality, thick walls, fixed together with well-constructed joints, there are still two places where sound can seep through:

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• Imperfect door seals
• Ventilation channels

Imperfect door seals

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The cheapest way to keep a door closed is with single point magnets. They make it look like the door is closed, but in reality they apply unequal pressure throughout the perimeter of the door. Without perfect installation, this creates tiny gaps where sound will escape. Even if there are no gaps when the booth is first installed, it’s unlikely to stay that way very long.

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Also consider the rubber seals around the edge of the door. Using separate rubbers is easier than using a single continuous rubber, but leaves gaps. Be aware of products that do not use rubbers around the whole perimeter of the booth.

Ventilation channels

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How can you allow air to travel freely, while still blocking sound? It’s a challenge that many cheap booths ignore, by using holes in the booth with no ventilation channels. (On cheaper booths, you can often see straight through them!)

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The solution is similar to that used in the construction joints. The longer and more convoluted the ventilation channel, the less likely sound is to escape. In higher-quality booths, those channels will also feature both soft materials to absorb sound and harder materials to break soundwaves.

What to look for:

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• Magnetic strips instead of single pointmagnets
• Connected rubber seals instead of separate seals
• Convoluted ventilation channels
• Soundtraps within ventilation channels

What to avoid:

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• Single point magnets
• Separated rubber strips
• Rubber strips not being used on all four sides of the door
• Holes in the booth with no ventilation channels

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How much soundproofing do you really need?

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So you know what makes a well-soundproofed booth. But how do you ensure you get the perfect fit for your requirements and avoid overpaying?

To choose the right soundproofing level, follow these steps:

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• Identify where you’ll be placing the booths
• Assess the level of noise in those places
• Decide whether you need to stop sound coming in or leaking out
• Identify what level of soundproofing is important

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What does an ISO rating mean and can I trust it?

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ISO 23351 was developed as a standardisedway to test the soundproofing of booths. Most booths will be described as ClassA (30–33dB) or Class B (25–30dB), but these are pretty broad ranges. It’s best to ask for the actual decibel rating. Also bear in mind that sound lab testing facilities vary and there is a standard deviation in testing anyway. If you arecomparing booths with similar ratings, it’s best to test them in person.

A rule of thumb...

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Soundproofing is the main reason you are buying a booth, so don’t compromise too easily. However, for most situations, around 28dB soundproofing will give you great results and you’ll find products that don’t cost over €8,000

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Are you paying for a booth or paying for the reseller mark up?

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One final point could save you a lot of money. Resellers can add 40% or more, transforming a relatively affordable booth into a more expensive purchase, without improving the quality. With the mark-up, expensive booths can sometimes be cheap booths in disguise!

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