Understanding Sound Masking: Enhancing Acoustic Comfort and Privacy

In modern office environments and other shared spaces, managing noise levels can be challenging. Sound masking is a powerful tool for creating comfortable and productive environments by reducing noise distractions and enhancing speech privacy. By reducing noise distractions and enhancing speech privacy, sound masking technology creates a more consistent and comfortable acoustic environment. Sound masking is a proven acoustic strategy used to enhance speech privacy, reduce distractions, and improve comfort in shared environments.

Adding sound to a space actually makes the space seem quieter. It sounds counter-intuitive but it’s true. This is because the added sound reduces the intelligibility of human speech.

Sound Masking vs Noise Cancelling: What's the Difference?

What is Sound Masking?

Sound masking involves adding a background sound to an environment to cover up unwanted noises. It relies on auditory masking. Sound masking is the inclusion of generated sound into an environment to mask unwanted sound. Sound masking is not a form of active noise control; however, it can reduce or eliminate the perception of sound. Sound masking is applied to an entire area to improve acoustical satisfaction, thus improving the acoustical privacy of the space. Sound masking means controlling background sounds in a developed environment.

Sound masking is an ambient sound, similar to the sound of airflow, that’s specifically engineered to the frequency of human speech you can target conversational distractions and make them less distracting. By introducing a consistent background sound, sound masking raises the ambient noise level in an environment, making speech noise less intelligible and therefore less distracting.

It is significant and prioritizes modifying the background sound; however, there is substantial evidence indicating that acoustical satisfaction within a space cannot be guaranteed without consideration of the three principal parameters of architectural acoustical design.

A sound masking system can be used to reduce the impression of intruding sound (reducing annoyance, distraction) and improve acoustic privacy (including speech privacy).

How Sound Masking Works

Sound masking systems use speakers (emitters) to distribute a carefully engineered sound throughout a space. Sound masking systems use a network of emitters-usually installed above drop ceilings or mounted directly in exposed ceiling spaces-to broadcast a specially tuned sound that masks human speech. By making conversations less intelligible, the system improves speech privacy and reduces the cognitive load caused by overheard speech.

Modern acoustic masking systems are discreet, scalable, and easy to tune based on your project’s needs. Volume control, equalizer settings, paging/music input mixing, schedule programming: the software lets you apply every imaginable adjustment instantly on a system-wide or per zone basis.

Adaptive volume makes use of ceiling-mounted noise sensors and the advanced signal-processing technology embedded in our controllers to automatically adjust the sound masking volume up or down based on how loud or quiet the office gets throughout the day. That mid-morning rush ends and the office space goes practically silent? The sound masking volume decreases back to where it was before the rush. It's the mid-morning rush at work and the office is buzzing with activity, conversations and potential distractions? The sound masking volume gently goes up. And it'll continuously move up and down like that: up to its maximum allowed level, down to its minimum effective level, and anywhere in between, in reaction to changes in office activity level over time. Simple enough?

Sound Masking vs. White Noise

Unlike white noise, sound masking is specifically engineered to match the frequencies of human speech and to sound comfortable, even pleasant, to the human ear. Sound masking specifically blends into the background and is less noticeable, unlike white noise, which includes all frequencies at equal intensity. White noise contains all frequencies at equal intensity, making it more noticeable and potentially irritating. White noise and sound masking are not the same. White noise plays all frequencies at once, often resulting in a harsh or fatiguing sound. Sound masking, on the other hand, is engineered to match speech frequencies and delivered at just the right level to enhance privacy without becoming noticeable.

Applications of Sound Masking

Sound masking systems are useful for a variety of reasons; they can block noise as well as provide white noise if a space is too quiet. Sound masking is provided in the area where conversations should not be heard - not necessarily in the area where the conversation is taking place.

Sound masking excels in large or open-plan environments where traditional soundproofing methods aren’t practical. Sound masking is an effective solution in masking intruding noise.

Here are some common applications:

• Open Offices: Open offices often suffer from noise distractions. Open office plans - open offices can be either too quiet (where someone dropping a pen in the next cubicle is distracting) - or too noisy (where the conversations of others in the office make it impossible to concentrate).
• Private Offices: Private offices and other enclosed spaces often appear to provide privacy but do not. Many times, walls are lightweight and do not extend to the ceiling deck, but only to the ceiling tile. In these cases, sound can easily travel through partitions or over the walls.
• Public Spaces: Public spaces - sound masking is useful for reception areas, pharmacies, waiting rooms, and financial institutions.
• Healthcare: For government organizations or industries such as healthcare, privacy is not only important, but a legal requirement. In healthcare, it plays a vital role in meeting speech privacy codes. For instance, a psychiatrist would not want those in the waiting room to overhear a private conversation with a patient, so sound masking is provided in the waiting area, but not in the psychiatrist's office.

Benefits of Sound Masking

Absolutely any business can benefit from improved worker comfort and improved efficiency-yes, even those with open office plans. We’d hazard a guess: absolutely! You want to enhance worker comfort.

Here's how sound masking can help:

• Enhanced Speech Privacy: Ensuring conversations remain private is crucial in settings like legal firms or HR departments.
• Reduced Distractions: With a sound masking system, though, you create a distraction-free workspace in which everyone can work at the noise level that best suits them.
• Improved Productivity: Aufderworld designs and installs sound masking devices so employees can be more efficient, and guests and tenants can block out distracting noises from others.
• Worker Wellbeing: In addition to decreasing efficiency, excessive noise can also wreak havoc on your workers’ emotional wellbeing. Stress from constantly being asked to perform in less than ideal conditions can tank worker morale. A sound masking system makes sure this doesn’t happen.

Types of Sound Masking Systems

The plenum is the space between a "dropped" ceiling and the upper deck to the floor. There are two primary types of sound masking systems:

• Plenum Sound Masking Systems: In plenum sound masking systems, which employ a network of loudspeakers located completely within the plenum, were the first such systems developed and have been in use since the 1960s. Plenum-based speakers typically range 4-10 inches (10-25 cm) in diameter and generally face upwards, towards the upper deck. This is done to reflect sound from the speakers to broaden, as much as possible, the footprint from the speaker in the work area.
• Direct Field Sound Masking Systems: Direct field sound masking systems have been in use since the late 1990s. The name takes after the mechanics of sound transmission which considers the "direct sound path" from the loudspeaker emitted towards the recipients (listeners) underneath. Initially used as an accessory for open office cubicles, direct field systems have been fully integrated into at least one open office furniture system and have been designed to be installed both in dropped ceilings and in offices without any absorptive ceiling systems.

When installed in dropped ceilings, direct field systems use speakers that are mounted facing down. When a ceiling tile is not available, they are mounted facing down on any available structure, sending the masking noise directly into the intended space. Theoretically, a direct field system would benefit from speakers that are omnidirectional, meaning that they transmit energy equally in essentially all directions. However, direct field systems require tighter arrays of loudspeakers given the polarity of the emission of sound.

Key Considerations for Implementation

The greatest challenge in any sound masking project? To generate the recommended ideal sound masking spectrum while taking into consideration the space's unique design attributes. Room size, ceiling type, acoustic tiles, wall finishes, and office furniture all have an impact on how efficient sound masking is at drowning out distractions and improving acoustic privacy.

As with any commercial-grade sound masking system, an in-plenum sound masking system requires proper layout design, commissioning, and verification of the performance. Disregarding the importance of any of these stages in implementation will result in a sound masking system that does not perform according to the specifications of an acoustician.

Here are some tips for successful implementation:

• Avoid placing too many emitters in one area, as this can lead to an overly dampened sound environment.
• Failing to identify and cover key reflection points can result in suboptimal sound quality.

Advanced Features

Only the most sophisticated sound masking systems can control the background sound level and spectra of masking sound accurately and precisely throughout a space, made possible only with the smallest zones (spatial limits around a speaker) and sophisticated electronics and software. Uniformity can be achieved by adjusting the acoustic output of individual or a small groups of speakers.

Our system's automatic equalization process allows it to adapt itself to an endless array of office environments. It analyzes the acoustic response and the background noise in the space covered and uses this data to figure out the spectrum needed to generate a soft, neutral and pleasant masking sound. Did we say minutes? Actually, our patented technology makes it possible to calibrate individual sound masking zones in less than a minute, with equalization done in both 1/3 octave and 340 narrow band spectra. The quality of calibration is assessed in real-time by our system’s integrated frequency analyser.

Adjustments routinely include changes in the output volume and output spectra of individual speakers. Soft dB sound masking combines both the flexibility of networked systems and the cost efficiency of more traditional centralized systems. It can simultaneously distribute sound masking, paging and ambient music throughout an endless array of distinct office zones-each of which with their own specific volume levels, input mixing and EQ settings-across multiple office floors or buildings even.

Masking: A Deeper Dive

Suppose you enter a restaurant with a friend, mid-conversation. As you enter, you are greeted by the background noise of other patrons’ conversations. You and your friend begin to speak louder so you can hear one another. You’ve just experienced masking, a very familiar yet fascinating phenomenon that many of us encounter every day without even noticing.

Masking is “the process by which the threshold of hearing of one sound is raised by the presence of another'' [1]. In this restaurant experience, your friend’s voice functions-to you-as the masked sound (known in lab-based research as the test stimulus) and the background noise of the restaurant patrons functions as the masker; this background noise raises your masked detection threshold-the minimum audible intensity of the masked sound (your friend’s voice) in the presence of a masker (the background din of the restaurant) making it harder to detect [1].

Masking can be partial, when the masked sound is still audible (but softer), or total, when the masked sound can’t be heard at all [2]. Additionally, there are several contexts in which masking can occur, including simultaneous masking (with two concurrent sounds), forward masking (when the stimulus occurs after the masker), backward masking (yes, when the stimulus precedes the masker!), central masking (when the masker is presented in one ear and the stimulus in the other) [2], energetic masking (peripheral masking, due to interferences) and informational masking (higher-level masking which is not energetic) [1], [3].

Simultaneous masking, as the restaurant experience above describes, is by far the most well-understood type. It is a direct consequence of competition on the auditory nerve [1], occurring when the masker activates the receptors of the inner ear that would have otherwise been activated by the masked sound, meaning the masked sound does not fully reach higher levels of the auditory system. The activation of these receptors strongly depends on critical bands, a very important concept in psychoacoustics.

Critical bands act as a series of band-pass filters characterizing the behavior of our basilar membrane. A band-pass filter lets through only a part of a sound’s spectrum. It has a bell-curve shape and is quantified by its center frequency (frequency value at the maximum height of the curve) and bandwidth (frequency distance between the two borders of the filter, where the energy of the curve is half the maximum value). Critical bands thus split the spectrum of an incoming sound into many frequency bands. The width of a critical band increases as the center frequency increases, but always covers the same distance on the basilar membrane [6].

Why do critical bands matter for masking? Simply put, critical bands determine when masking will occur, and when it won’t occur. For example, one sound (“sound A”) can mask another (“sound B”) if the distance between the two sounds’ frequencies is less than a critical band’s bandwidth.

If sound A’s bandwidth is quite narrow (i.e., it only covers a small region of the critical band it occupies), the masked detection threshold for sound B will be quite low (i.e., it will still be easy to hear). As sound A’s bandwidth grows wider, eventually becoming coterminous with the critical band, the masked detection threshold for sound B similarly grows (i.e. it will become very difficult to hear). Consequently, sound B must become louder (i.e., emit more sonic energy) to remain audible.

By measuring the masked detection thresholds of a tone with variable frequency, we can obtain a masked audiogram (or masking pattern), a curve often used to measure the masking effect generated by a fixed masker as a function of stimulus frequency [6]. Masked audiograms reflect the physical oscillation pattern of the basilar membrane provoked by the masker [2], [9]. In the case of a pure tone masker, their asymmetrical shape is affected by the level of stimulation.

In certain cases, masking will happen even if the test stimulus and the masker do not appear simultaneously. This scenario is often referred to as temporal masking, and results from higher level processes (e.g., cortical areas) [11]. We can experience temporal masking when the test stimulus occurs before or after the masker (as demonstrated here).