Preserved moss absorbs sound in the frequency range most relevant to speech, where conversations, keyboards and ambient noise occur. Based on verified measurement data, this article shows how effectively the different types of moss absorb sound, which type is suitable for each room and how much surface area is needed to produce a noticeable effect.
Preserved moss combines natural design with a measurable acoustic function. It acts as a porous sound absorber: when sound reaches its finely structured surface, part of the sound energy is converted into frictional heat instead of being reflected back into the room. The strength of this effect depends on the type and thickness of the moss as well as the construction method. All values below are based on reverberation-room measurements conducted in accordance with DIN EN ISO 354 and rated according to DIN EN ISO 11654.
What types of noise occur in offices, and which ones are genuinely disruptive?
Not every sound is equally disruptive. In open-plan offices, the perceived level of disturbance depends less on the volume of individual voices than on how clearly other people’s conversations can be understood. Speech intelligibility occurs mainly in the mid and high frequencies, which also include sibilant speech sounds, keyboards and office equipment.
| Frequency range | Typical indoor sources |
|---|---|
| 20 to 100 Hz | Infrasound from air conditioning, ventilation and building services |
| 100 to 250 Hz | Fundamental frequency of the human voice and low-frequency traffic noise |
| 250 to 2000 Hz | Speech intelligibility, phone calls, keyboards and movement within the room |
| 2000 to 6000 Hz | Sibilant speech sounds, paper, mouse clicks and tableware |
| 6000 to 20000 Hz | High-frequency equipment, fans and electronic signals |
The disruptive effect of office noise therefore lies mainly between 250 and 6000 Hz. Moss absorbs sound particularly effectively in this range. Very low frequencies below 250 Hz, such as the hum of a ventilation system, are absorbed less effectively by porous absorbers because of the way they work.
How does sound absorption with moss work?
Sound absorption is described by the sound absorption coefficient Alpha. A value of 1.00 represents complete absorption, while a value of 0.00 represents complete reflection. Because absorption varies depending on frequency, it is measured in individual frequency bands and also summarised as a weighted single-number value, Alpha w.
Across the entire frequency range, a plastered solid wall achieves only around 0.02 to 0.05. It therefore reflects almost all sound. A moss surface installed on the same wall changes this behaviour significantly, especially in the speech frequency range.
How effectively does each type of moss absorb sound?
The following overview shows the practical sound absorption coefficient for each octave band as well as the weighted single-number value Alpha w. All values were measured in a reverberation room in accordance with DIN EN ISO 354.
| Type of moss | 250 Hz | 500 Hz | 1000 Hz | 2000 Hz | 4000 Hz | Alpha w |
|---|---|---|---|---|---|---|
| Bun moss | 0.25 | 0.65 | 1.00 | 1.00 | 1.00 | 0.55 |
| Velvet Leaf | 0.30 | 0.70 | 0.80 | 0.85 | 1.00 | 0.60 |
| Reindeer moss | 0.20 | 0.40 | 0.65 | 0.70 | 0.80 | 0.45 |
| Plastered wall, comparison | 0.02 | 0.03 | 0.04 | 0.05 | 0.05 | < 0.05 |
Bun moss and reindeer moss were measured in the reverberation room at the University of Liège. Velvet Leaf was measured by the Dutch testing institute Peutz. All measurements were conducted in accordance with DIN EN ISO 354 and rated according to DIN EN ISO 11654. The reindeer moss results were additionally confirmed by an accredited testing laboratory in Finland. Values for the plastered wall are taken from standard building-acoustics literature.
Bun moss reaches the maximum value from 1000 Hz upwards and absorbs up to 100 percent of the incident sound in the speech frequency range. This makes it the highest-performing moss type for rooms with a high concentration of conversations. Velvet Leaf becomes effective at lower frequencies and provides the broadest coverage of the speech range. Reindeer moss absorbs up to 80 percent in the high-frequency range and is well suited to reducing sibilant sounds and harsh reflections.
Forest moss and jungle moss
Forest moss is a dense, flat-growing moss used primarily as a large-scale design element. Jungle moss combines moss with preserved plant elements to create a highly structured surface. Both contribute to sound absorption, but they are selected primarily for their visual appearance. For surfaces with specific acoustic requirements, we recommend bun moss or Velvet Leaf.
Which type of moss is suitable for which room?
| Room and situation | Recommendation |
|---|---|
| Open-plan office with many conversations | Bun moss or Velvet Leaf |
| Meeting or conference room | Velvet Leaf for broad effectiveness, bun moss for high performance |
| Reception area and lobby | Bun moss combined with reindeer moss for visual depth |
| Restaurants with tableware noise and conversations | Bun moss for the high-frequency range |
How much moss surface is needed for a noticeable effect?
The effect within a room depends not only on the type of moss, but above all on the installed surface area. As a rule of thumb, an absorbing surface equal to 15 to 20 percent of the room’s total surface area produces a clearly noticeable improvement. In an office with around 100 square metres of total room surface, this corresponds to approximately 10 to 20 square metres of moss.
A single small moss picture has a decorative effect and brings nature into the room, but it changes the reverberation time only slightly. A meaningful acoustic effect requires continuous or combined surfaces, such as a moss wall, several pictures distributed throughout the room or suspended ceiling rafts.
Does an air gap behind the moss improve performance?
Yes. The position of the absorber in relation to the wall affects absorption. When installed directly on the wall, a porous absorber works mainly in the mid and high-frequency range. Installing it with a gap behind it improves absorption, particularly towards lower frequencies.
The reason lies in the physics of the sound field: directly at a hard wall, the movement of air particles is zero, while it reaches a maximum at a certain distance in front of the wall. The closer the absorber is positioned to this maximum, the more sound energy it can absorb. For projects with requirements in the lower-frequency range, we can therefore supply moss surfaces with a ventilated backing or as suspended ceiling rafts on request.
Frequently asked questions about the sound absorption of moss
Does preserved moss absorb sound?
Yes. Preserved moss is a porous sound absorber that works in the speech-relevant range between 250 and 6000 Hz. Depending on the type of moss, it can absorb up to 100 percent of the incident sound in this range. Bun moss achieves the highest values.
Which type of moss absorbs sound most effectively?
Bun moss achieves the highest absorption in the speech frequency range and reaches the maximum value from 1000 Hz upwards. Velvet Leaf has the highest weighted single-number value and covers the broadest frequency range.
What percentage of sound does moss absorb?
This depends on the frequency. Bun moss absorbs up to 100 percent in the speech range, while reindeer moss absorbs up to 80 percent. A general percentage figure without a stated frequency is not very meaningful because sound absorption is always frequency-dependent.
Which standard is used to measure sound absorption?
Measurements are conducted in a reverberation room in accordance with DIN EN ISO 354, while the weighted single-number value is determined according to DIN EN ISO 11654. Greenfinity’s values are based on measurements by the University of Liège, the Dutch institute Peutz and an accredited testing laboratory in Finland.
How much moss surface is required for an office?
As a guideline, an absorbing surface equal to 15 to 20 percent of the room’s total surface area produces a clearly noticeable improvement. The exact area depends on the room’s size, geometry and use. We provide project-specific advice.
Does moss also absorb low frequencies?
Moss is most effective in the mid and high-frequency ranges where office noise occurs. Very low frequencies are absorbed less effectively. A construction with a ventilated air gap behind the moss can extend its effectiveness towards lower frequencies.
Advice for your project
Whether you are planning a moss wall, moss picture or suspended ceiling raft, we tailor the moss type, surface area and construction method to your room-acoustic objective and provide the verified performance data in a technical data sheet. Contact us for a no-obligation consultation.
