With more than 10 years of experience in the visual and acoustic field, In-Zee presents a diverse range of sound-absorbing products.

Offices, meeting rooms, canteens, waiting rooms and meeting areas. Within a building, each space fulfils an essential role in the experience of work, social interaction and personal well-being. In-Zee specialises in translating those specific functions into visual and acoustic comfort. Into interior designs that make staying pleasant. That create atmosphere and make an impression. Matching the purpose of the space, the appearance of the building and the designer's ideas. We inspire, advise and implement.

What is sound?

When designing a shared space, it is important to know how sound behaves in different situations.

Sound is created by vibration. Vibration produces sound waves that travel through the air. A sound wave consists of a high and low 'air pressure region' and its corresponding frequency.

Frequency is measured in Hertz (Hz), which is the distance between individual sound waves. Sound that vibrates quickly (high tone) has a short sound wave and thus a high frequency. A low tone vibrates slowly and has a longer sound wave, thus a low frequency. Sound pressure is measured by Decibel (dB).

Sound pressure represents the effective pressure of a sound relative to a reference value. The decibel value is therefore very diverse and is given non-linearly. For example, if the sound pressure level is multiplied by 10, the decibel value increases by 10 dB. Together, frequency and sound pressure form the basis of sound.

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Infographic acoustics without products WEB LR Infographic acoustics with products WEB LR

Controlling noise within an environment

Controlling sound is not always possible at the source. Think of a conversation, a buzzing computer or a slamming door. It is therefore more important to control sound throughout the environment. In a free environment, especially outdoors, sound always goes straight ahead. But as soon as there are obstacles in front of the sound, it will bounce off, deflect or reflect.

Below are some common effects that sound has to deal with and thus we can deploy or influence.


Absorption occurs when sound waves are trapped in a soft porous material. Depending on the thickness of the material, the absorption value is determined.


Diffusion occurs when a sound wave hits an object and is diffused and scattered by the hard and distorted structure of the material.


Reflection occurs when sound waves hit a hard surface with little or no absorption. The sound reflects at the same angle at which it enters.


Insulation occurs when the entire sound wave is stopped by a material. If the material is almost completely insulated but still allows a small amount of sound to pass through, this is called transmission. 


Diffraction occurs when sound bends itself around an object, or conversely, when it escapes through a small opening and then spreads out. Diffraction is tried to counteract as much as possible. There is talk of a 'leak' when diffraction occurs in an unintended environment.

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Reverberation or echo and how to avoid it?

Reverberation is a sound phenomenon that occurs when sound is repeatedly reflected in a room. The reverberant sound mixes with the original sound from the sound source.

This is also the direct difference between reverberation and echo. In echo, the original sound and the delayed sound are clearly distinguishable. Echo sound is often heard after the original sound has already stopped.

Both phenomena are often unwanted and perceived as unpleasant in most rooms. Fortunately, there are plenty of ways to remove reverberation from the room before it has a chance to reflect. This can be done, for example, by capturing the indirect sound. Often the indirect sound is reflected through the ceiling, which is why you want to place acoustic elements in that very location to prevent unwanted reflection. With our products and their placement, we always take this effect into account.

Calculating the right acoustic space

Reverberation time is the time it takes for the sound in a room to diminish by 60dB. Reverberation time is expressed in RT60 (Reverberation Time of 60dB).

A room with an RT60 longer than 2 seconds is perceived as echoing. Whereas an RT60 shorter than 0.3 seconds is considered 'dead'. The sound hits flat against the acoustic components in the room and is almost no longer reflected. To roughly calculate whether a room is acoustically correct, stay between 0.5 and 1.5 seconds of RT60.

T = the time in seconds how long the sound hangs in the room

V = the volume (volume) of the space

O = area of all acoustic material in this room (this may include sofas, carpets, acoustic system ceilings and even acoustic lighting and moss walls)

The formula to calculate the reverberation time goes as follows:

T = 0.16 x ( V / O )

Sound absorption

All objects and materials have acoustic values and characteristics. They can absorb, reflect or a combination of these. The way and effectiveness in which materials do so depends on frequency. Absorption coefficients help us understand how absorbent, or rather reflective, an object or material is. This is expressed in acoustic value (aw)

The softer, more porous and open a material is, the more sound it tends to absorb and thus the higher its acoustic value. A hard and rigid material is more likely to reflect sound and therefore has a lower acoustic value. The acoustic value is an average number of the absorbed energy tested on a large scale of frequency tones.

For example: PET Felt free-standing in a room has an average acoustic value of 0.45 across all the various frequency tones. This means that the material absorbs 45% of the sound energy it comes into contact with. This also indicates that the remaining 55% will be reflected, or pass through the material (transmission).

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