Sound Masking: When It Makes Sense and When It Doesn't

Why you can hear more in a quiet office than in a noisy one

Speech intelligibility depends on the difference between the speaker’s voice and the background level in the space. The background is the sound that is always present, including ventilation, equipment and surrounding activity. It is also referred to as the background level or background noise. When the background is quiet, even a quiet conversation can be understood from the other side of the room. When the background level is higher, the same conversation becomes less intelligible.

In an acoustically treated open-plan office, this difference can be significant. Carpets, suspended ceilings and absorptive partitions reduce the overall noise level. At the same time, however, they also reduce the background level against which surrounding speech would otherwise become less intelligible. A conversation from the other side of the floor can therefore become particularly easy to understand in a space that has otherwise been acoustically treated.

Sound masking works with this difference. It adds frequency-shaped sound designed to mask the frequency range of human speech without drawing attention to itself. The objective is for you to know that someone nearby is speaking without being able to understand the conversation.

How sound masking differs from acoustic treatment and sound reinforcement

These three solutions are often confused in enquiries, and confusing them results in a proposal for something different from what the customer actually needs.

Acoustic treatment changes how sound behaves within a space. It reduces reverberation and reflections, making the environment calmer. Reverberation is the period during which sound continues to decay in a room after the original source stops. Acoustic treatment does not directly solve the intelligibility of other people’s conversations because that depends on the background level.

Sound reinforcement delivers content that is supposed to be heard and understood, such as a presenter’s voice, music or announcements.

Sound masking introduces sound that is intended to be audible but does not need to carry information because its purpose is to mask other sound. It operates continuously and uniformly. In the ideal situation, nobody consciously notices it.

What it looks like in the room. Acoustic treatment is visible in the form of panels on walls and ceilings. Sound reinforcement is also visible because loudspeakers are positioned to cover specific areas and reproduce content. Sound masking is usually noticeable only when you deliberately look for it. Many small sound sources are distributed throughout the space. Together, they create one uniform background sound. The system consists of the signal source and these distributed emitters. It is a permanent installation.

What it sounds like. It sounds similar to quiet ventilation running somewhere in the background. If you can point directly to where the sound is coming from, it is drawing attention to itself and is no longer performing its intended function correctly.

Our article on acoustic treatment versus a more powerful system explains which approach is appropriate for different types of problems.

Spaces where sound reflects from hard surfaces and where the room itself largely determines the result are covered in our article about an acoustically challenging space.

MediaTech builds sound masking solutions using Biamp QtPRO and DynasoundPRO systems.

Where sound masking makes sense

The system makes sense when three conditions apply at the same time. The space is open or transitional, the background is quiet and conversations take place that are irrelevant to the people nearby.

In practice, this applies to four main types of spaces.

• Open-plan offices, particularly where employees need to concentrate or regularly make calls from their desks.
• Waiting rooms and reception areas, where conversations with clients take place while other people are sitting only a few metres away.
• Corridors and open circulation areas outside meeting rooms, where conversations taking place inside may otherwise be intelligible.
• Open spaces where sensitive matters are discussed. Improving speech privacy is one of the significant benefits of sound masking.

These four types of spaces exist across many industries. The same three conditions can be found in a medical practice, a bank branch or a hotel lobby. Nine examples where this commonly occurs are:

• Medical practices, clinics and pharmacies. Diagnoses and medication are discussed at the desk while other patients sit in the same room.
• Bank, insurance and leasing branches. Advisers work in an open environment while discussing income, debt and repayments with clients.
• Law, tax and accounting offices. Open areas outside meeting rooms and places where employees speak to clients by phone.
• HR departments with an open-plan layout. Payroll and personnel matters are discussed at desks while neighbouring employees are within hearing distance.
• Public-sector and municipal client centres. Service desks are positioned next to each other while visitors discuss matters that are irrelevant to other people waiting nearby.
• Coworking and shared offices. People from different companies sit next to each other while each person discusses their own business by phone.
• Room numbers, names and payment details may be spoken aloud at a counter in front of a queue of waiting guests.
• Libraries, study rooms and learning spaces. Silence is expected, which means every word from the neighbouring desk can become clearly audible.
• Restaurants, bistros and bars with quiet operation. Tables may be close together and guests can understand conversations from neighbouring tables.

Hospitality environments can fall into either category, and the difference may depend on the time of day rather than the venue itself. During a business lunch, dinner in a table-service restaurant or breakfast in a hotel restaurant, the background may be quiet enough for conversations at neighbouring tables to be intelligible. In the same venue on a Friday evening, background noise may already be high enough that there is nothing left to mask. If guests have to raise their voices to hear each other and feel fatigued after an hour, the problem is more likely to require acoustic treatment.

The three conditions matter, not the industry. If one of them is missing, sound masking will not improve the situation simply because the environment happens to be a clinic, bank or office.

Sound masking is designed for the complete space. Both the level and frequency response are adjusted on site. The system is tuned by zones because an open environment does not have identical acoustic conditions everywhere. A zone is a part of the space with its own settings.

When you do not need sound masking

When background noise is already high. In a manufacturing hall, a technology-heavy operation or a space with noisy ventilation, surrounding speech is already masked naturally. Adding more sound would simply increase the overall level without improving anything.

When nobody in the space needs to concentrate. In a shop, warehouse or space that people simply pass through, there may be no meaningful distraction or speech-privacy problem to address.

When the actual problem is reverberation rather than intelligibility. If the room echoes, people raise their voices and feel fatigued after spending a day there, the appropriate solution is acoustic treatment. Sound masking would simply add more sound to an environment where excessive sound is already part of the problem.

When the issue concerns a single room that can be closed. For one meeting room or executive office, it is usually better to address sound transmission directly through the doors, seals and partition construction.

When the space is rented only for a short period. The system is designed around a specific floor plan and tuning configuration, so it cannot be moved as easily as furniture.

Six things that determine the proposal

Your brief does not need to specify a particular sound masking system, but it should include these six things.

• What exactly is disturbing you. Can you understand surrounding conversations, or is the whole space simply noisy and tiring?
• How many people work there and what the layout looks like. A completely open floor is addressed differently from a space divided by furniture, booths or partitions.
• What the current background level is like. If it is already high, the reason for installing sound masking becomes weaker.
• Whether the space has a suspended ceiling. The ceiling construction affects both the installation method and its complexity.
• Where sensitive conversations take place. This determines which zones should receive priority.
• Who will manage the system. Once commissioned, it runs automatically, but somebody still needs to know what to do when the office layout changes.

The first point determines whether you receive a proposal for the correct solution in the first place.

What goes wrong when the system is implemented poorly

With sound masking, a poorly implemented system can be worse than having no system at all. Compare it with other technology in a building. A meeting room that does not work is simply not used. A poorly configured sound masking system affects employees throughout the entire working day and changes a space that may previously have worked reasonably well.

The system is noticeable. If the level is too high or the frequency response is shaped incorrectly, people perceive it as ventilation noise and begin complaining about it.

The system solves nothing. If the level is too low, the difference between speech and the background remains effectively unchanged and conversations are just as intelligible as before. You pay for the installation but the original problem remains.

The space sounds uneven. A system configured as one large zone can create areas where the masking level is excessive and others where it is insufficient. Employees may describe the result by saying that it is difficult to concentrate at certain desks.

The system becomes incorrectly tuned after a refurbishment. Partitions, furniture and occupancy all change the way sound behaves. A company that regularly reconfigures its open-plan office needs to know who will retune the system afterwards. This responsibility should be agreed in advance.

Ask what happens after handover.

• Who commissions and tunes the system?
• Who retunes it after a refurbishment or layout change?
• What happens if employees begin complaining?

Our article on the division of responsibilities between IT and the AV integrator explains where responsibility for audiovisual technology sits between your IT or facilities team and the supplier.

Frequently asked questions

What is sound masking and how does it work? It is a system that adds frequency-shaped background sound to a space so that surrounding speech becomes less intelligible. It works by changing the difference between the speaker’s voice and the background level, which is one of the factors determining intelligibility. You can therefore still hear that someone nearby is speaking without understanding the conversation.

What is the difference between sound masking and acoustic treatment? Acoustic treatment changes how sound behaves in a room by reducing reverberation and reflections using absorptive materials. Sound masking does the opposite in one specific sense: it adds sound to the environment in order to mask speech. Acoustic treatment addresses reverberation and noise-related fatigue, while sound masking addresses the intelligibility of surrounding conversations.

When does sound masking not make sense? It does not make sense when background noise is already high, for example in a manufacturing environment where surrounding speech is naturally masked. It is also unnecessary where nobody needs to work with sustained concentration, where reverberation rather than speech intelligibility is the actual problem, or where the issue involves a single enclosed room that can be addressed more efficiently through the door and partition construction. In the first two cases there is little to mask, while in the others the solution belongs to a different discipline or to building construction.

Can sound masking help protect sensitive information? It addresses one specific layer: whether people nearby can understand a conversation. It does not control who has access to the information or what happens to the information afterwards, so sound masking by itself is not a complete data-protection solution. It makes the most sense at receptions, waiting rooms and open workplaces where people discuss matters aloud that are irrelevant to those around them.

Which sound masking systems does MediaTech use? MediaTech builds solutions using Biamp QtPRO and DynasoundPRO. These systems are designed for open-plan workplaces, waiting rooms, corridors and other open environments. The system is designed for the complete space and both the sound level and frequency response are adjusted on site.

What happens if the system is configured incorrectly? It may either become noticeable as background noise and cause complaints, or it may be too quiet and leave surrounding conversations just as intelligible as before. A third problem is unevenness, where masking is excessive at some desks and insufficient at others. Poorly implemented sound masking can be worse than having no system because employees are exposed to it throughout the working day.

How much does sound masking cost? The price depends on the floor plan, the number of zones and the problem being addressed, so an exact amount can only be determined from a project proposal. As a general indication of project scale, a smaller sound system project starts at around €3,000. This figure refers to the project as a whole and cannot be used to derive the price of sound masking itself.

Next step

Send us the floor plan of the space and describe what is disturbing you and how many people work there. We will assess whether sound masking is the appropriate solution.

Send us the floor plan and a description of the problem.