Acoustic Knowledge
Glossary
The auditory sensation caused by an acoustic wave. An acoustic wave are vibrations travelling spherically in every direction as fast as 340 m/s transferring energy, which produces the sensation of loudness measured in dB. Another feature of an acoustic wave is its frequency measured in Hz, which produces the sensation of pitch of sound.
All unwanted, unnecessary or disruptive sounds, such as background chatter, alarms, telephone rings, buzz of electrical devices, street sounds. Remaining in a noisy environment may lead to decrease in concentration, higher number of mistakes made, and in the long run – health problems.
Defined as the length of time required for the sound to quiet down from the moment of its source being switched off. As sound waves strike hard surfaces (i.e. concrete, glass) they are repeatedly reflected before they gradually lose their energy – this results in the effect of reverberation or echo. Rooms with excessive reverberation time feel uncomfortable and make it difficult to focus and have conversation. The optimum reverberation time depends on the intended use of a room (for office spaces the optimum reverberation time is 0.5–0.6 sec., and for conference rooms 0.8–1.0 sec.). In order to reduce the reverberation time, it is necessary to increase the sound absorbing surfaces in the room.
Sound absorption is the ability of a given material to partially stop the energy of a sound wave and change it into unnoticeable thermal energy. Absorption is measured according to ISO 354 norm and expressed as the sound absorption coefficient αw between 0 (total reflection) and 1 (total absorption) and classes A–E.
List of sound absorbing products:
The ISO 354 norm defines the ability of a given material to absorb the acoustic energy, expressed by the sound absorption coefficient (αw between 0 and 1). The result is referred to the sound absorption classes table, where A depicts the highest qualities, and E – the lowest:
- class A – αw between 0.90 and 1.00
- class B – αw between 0.80 and 0.85
- class C – αw between 0.60 and 0.75
- class D – αw between 0.30 and 0.55
- class E – αw between 0.15 and 0.25
Ability of partitions (such as doors, walls or free-standing acoustic screens) to reduce the level of sound wave energy transmitted through it. The acoustic partition walls of high insulating qualities act as important acoustic barriers between various spaces and between the source of noise and the recipient. Insulation qualities of free-standing screens is measured according to ISO 10053 norm. It is defined by the level of noise reduction, which means the decrease of sound level expressed in dB.
List of products of the highest acoustic insulation qualities:
Energy carried by an acoustic wave determines the loudness of sound. It is referred to as sound level and measured in dB (decibel). The hearing range of a human ear is between 0 dB (perception threshold) and 130 dB (pain threshold). Examples of sound levels:
- 15 dB – leaves rustling
- 35 dB – library
- 50 dB – quiet office
- 60 dB – typical conversation
- 75 dB – telephone ring
- 120 dB – jet plane take off
Frequency of air vibrations carried by an acoustic wave is expressed in Hz (Hertz). This unit depicts the quantity of air vibrations per second. Frequencies audible to a human ear are between c. 16 Hz and c. 20,000 Hz. Human speech and sound of office equipment usually fall within the range of 100–5,000 Hz, and this is the interval used for testing sound absorbing and insulating products.
This term defines how well we understand verbal communicates. Hearing itself does not mean that we comprehend the message. Speech transmission can be measured and is expressed by Speech Transmission Index (STI) in the range of 0–1. Proper speech transmission is very important in the rooms dedicated to verbal communication, such as conference halls, auditoriums, classrooms.
Spaces and Solutions
The problem of excessive, distracting noise is very common in offices, especially the open space ones.
Underlying causes
- Loud conversations of co-workers, distracting familiarity of words spoken by other people;
- Work stations noises (keyboards/telephone rings etc.);
- Loud footsteps of people walking in the corridors or among desks;
- Operating office equipment (i.e. printers), which – according to research – can distract and decrease work efficiency even by 66 percent;
- Wrong office arrangement – quiet zones (for concentration) intermixed with the zones of loud conversations (teamwork);
- Lack of separate, isolated places for phone calls / informal meetings.
Solutions
Implementation of solutions towards shortening the reverberation time, better separation of individual work stations and creating zones dedicated to various activities (zone for concentration separated from phone call zone and team work / informal meetings zone). Another effective solution is isolating the sources of noise (i.e. office equipment) to prevent the sound reverberating in the room as it bounces off hard surfaces.
We recommend
- ceiling panels of very good sound absorption qualities, along with wall panels in place of hard surfaces,
- desk panels between work stations and free-standing partition walls or ceiling-hung panels separating groups of employees,
- floor covering which shortens the reverberation time and reduces the footstep noises.
Recommended products
A conference room is a key space in companies based on verbal communication, therefore the requirements concerning sound reverberation time should be more rigorous here than in other office spaces.
Underlying causes
- Scarce furnishing and hard surfaces (often at least one glass wall), which cause reverberation during group conversations. This can generate the flutter echo – sound waves bouncing off opposite walls numerous times, resulting in the unpleasant metallic sound;
- Noise generated by conversations during a meeting makes it difficult to understand what individual participants are saying. It can also cause problems during teleconferences;
- High level of chatter causes the participants to raise their voices, which makes the conversations audible outside the room (compromised confidentiality), as well as tiresome, and so influence on their efficiency.
Solutions
Installation of products of the highest sound absorbing qualities for shortening the reverberation time and reduction/elimination of the flatter echo effect. It is also necessary to provide proper insulation of doors and walls of the room.
We recommend
- free-standing columns (if impossible to fix panels on the walls or ceiling) or wall panels (on two neighbouring walls, if possible),
- ceiling panels of high sound insulation qualities (if possible to be fixed).
Recommended products
Small, confined office spaces are also prone to noise and reverberation, which cause work place discomfort, decrease of efficiency and concentration.
Underlying causes
- Hard surfaces on the walls (often at least one glass wall in the conference room) and ceiling (elements of drop ceiling) cause reverberation during group conversations. This can generate the flutter echo – sound waves bouncing off opposite walls numerous times, resulting in the unpleasant metallic sound;
- Insufficient sound insulation of partitions/walls between work stations, which makes conversations audible in the next room/office space (compromised confidentiality) and disturbs the work process;
- High level of chatter causes the employees to raise their voices, making conversations more tiresome.
Solutions
Installation of products of the highest sound absorption qualities. It is also necessary to increase the insulation of doors and walls in the room.
We recommend
- free-standing columns (if impossible to fix panels on the walls or ceiling) or wall panels (on two neighbouring walls, if possible),
- ceiling panels of high sound insulation qualities (if possible to be fixed).
Recommended products
The company canteens and break-out areas are prone to noise and reverberation due to their function. Under these circumstances, having a chat, at a meal for example, becomes annoying, tiresome and uncomfortable (and the lunch time should be dedicated to regeneration). Additionally, if the break-out areas are designated within the general office space, they may produce noise disruptive to other employees.
Underlying causes
- Loud conversations all around generate high level of noise, enhanced by high reverberation (numerous hard surfaces plus larger cubic capacity of such spaces);
- Buzz of appliances (i.e. coffee maker), clutter of cutlery and plates add to the general level of noise;
- If such spaces are used for large company meetings, for example, the meetings become tiresome due to high reverberation.
Solutions
Reducing the reverberation by means of sound absorbing materials on the ceilings and walls. If it is not possible to separate such a space with walls and doors (for break-out areas), it is necessary to “close” the space with proper acoustic partitions.
We recommend
- free-standing partition walls of high sound insulation qualities and maximum height possible,
- ceiling and wall panels of high sound insulation qualities (if possible to be fixed).
Recommended products
It is a key space dedicated to verbal communication, therefore the requirements concerning reverberation time are very restrictive in this case. Additionally, the badly acoustically insulated classroom or lecture hall can make the use of multimedia aids very inconvenient.
Underlying causes
- Hard surfaces on the walls and ceiling cause reverberation, which can generate the flutter echo – sound waves bouncing off opposite walls numerous times, resulting in the unpleasant metallic sound;
- Extensive chatter generates noise which makes a lecture illegible, and the teacher needs to raise their voice. This leads to the loss of focus, and fatigue;
- Sounds of shifting furniture (desks, chairs).
Solutions
Installation of products of the highest sound absorption qualities, reducing the reverberation. It is also necessary to increase the insulation of doors and walls to avoid sound travelling between neighbouring rooms.
We recommend
- free-standing partition walls (if impossible to fix panels on the walls and ceiling) or wall panels (on the back wall of the room, if possible, to avoid the sound travelling back to the lecturer),
- ceiling panels of high sound insulation qualities (if possible to be fixed).
Recommended products
Research shows that shops with bad acoustic environment can lose even 28 percent of their turnover. Customers who do not feel well in the store look at fewer products or simply leave the place. Such spaces need good ambiance, created by music, right temperature and lighting.
Underlying causes
- Excessive reverberation caused by large cubic capacity of the room and hard surfaces;
- Loud noise generated by the customers.
Solutions
Reducing the reverberation time to decrease the level of noise, improve speech transmission and create a more pleasant ambiance. As the shop area needs to remain an open space with products exposed in all available places, the sound insulating elements must be fixed on the ceiling, which is the most absorptive surface.
We recommend
- ceiling panels of high sound insulation qualities,
- wall panels (if possible to be fixed).
Recommended products
Restaurants and other places of similar function need very good ambiance, which cannot be achieved without proper acoustic comfort.
Underlying causes
- Noise generated by large numbers of people in the room, clutter of cutlery and sometimes the buzz of kitchen appliances;
- Long reverberation time due to large cubic capacity and hard surfaces in the room.
Solutions
Reducing the level of noise without excessive quantity of sound absorbing materials. In such spaces it is acceptable to hear other conversations and some background noise (chatter). We need to retain the proper speech transmission at a given table and limit it between tables. Therefore, on-spot approach is required.
We recommend
- ceiling panels of high sound insulation qualities;
- wall panels (if possible to be fixed) to help reduce the general level of noise.
Recommended products
Hotel rooms might not be spaces most prone to generating noise, but due to their function their acoustic comfort is especially important.
Underlying causes
- In case of scarce furnishing and large number of hard surfaces, some larger hotel rooms reverberate excessively, which adversely affects the comfort of conversations or watching TV.
Solutions
Reduction of reverberation time by means of sound absorbing panels. Due to the function and height of such spaces, the only possibility are the wall panels, which ensure a cosy, homey atmosphere.
We recommend
- wall panels of high sound insulation qualities, possibly decorative.
Recommended products
Problems and solutions (Q&A)
Echo (reverberation) results from sound waves being repeatedly reflected by hard surfaces in the room. Solving this problem requires shortening the reverberation time by means of sound absorbing products fixed on the walls or the ceiling. In case of small spaces with glass walls, it is useful to provide free-standing sound absorbing columns. The important parameter of these products is their sound absorbing quality (measured according to ISO 354 norm) – higher absorption will ensure better effects.
Recommended products: Blocks, Canvas, Puzzle, Tower, Shell, Print
One solution could be separating workstations with partition walls of high acoustic insulation qualities. Attention should be paid to the absorbing characteristics of these panels – high absorption parameters will prevent reflection of sounds and reverberation. The screens can be desk-mounted (Duo) or free-standing (Wall), and to fulfil their function they need to reach at least as high as the nose level of a sitting person. It is also worth providing the employees with designated phone call zones, such as free-standing telephone booths of high acoustic insulation qualities.
The most common cause of problems with understanding speech in spaces such as conference rooms is excessive reverberation time. Reverberation is generated when the voice is reflected by hard surfaces, such as walls, ceilings and floors, but cannot be muted due to scarce furnishing, for instance. The solution is to install the adequate quantity of products of high sound absorption parameters to reduce the number of sound waves reflections and decrease reverberation.
Recommended products: Blocks, Canvas, Puzzle, Tower, Shell, Print
You should start with checking the construction and tightness of the door – removing excessive slits should solve the problem to a certain extent. If the noise is still transmitted, a consult with an architect or an acoustic professional will be necessary. An immediate solution is reducing the level of noise in the neighbouring rooms by means of proper acoustic panels.
Solving this problem requires isolating the printing area from work stations. This can be achieved by means of free-standing panels of high acoustic insulation qualities (Wall). Additionally, it is worth providing sound absorption possibly closest to the source of noise – installing wall panels next to the equipment, for example.
The noise of operating air conditioning usually consists of sounds of medium frequencies resulting from badly designed installation. Solving this problem requires increasing sound absorption in the ventilation ducts, using air inlets of low noise level or additional sound absorbers. It is also useful to shorten the reverberation time in the room and thereby reduce the noise level. The sound absorbing products can be fixed on the walls or ceilings (if possible).
The solution is to create a special phone call zone, for example with telephone booths of high sound insulation qualities. These mobile free-standing modules are easily installed in an open-plan office. Moreover, several booths will naturally divide the large open space into smaller areas, facilitating concentration due to better acoustics of the room. It is important to choose products of good insulation parameters (blocking the outside noise and making conversations inaudible to others), high sound absorption qualities inside (to avoid reverberation during the call), proper ventilation (to make a long phone conversation or focused work convenient), as well as ergonomics and facilities inside the booth (proper seat, access to socket, accurate lighting coming from the outside and inside).
Recommended product: Space S
Solving problems of such spaces requires separating work stations with partition walls of high acoustic insulation. It is important that the walls have additional sound absorption qualities on both sides to prevent sounds from being reflected and thereby aviod reverberation. The best effects will be achieved by means of free-standing screens (Wall) at least as high as the mouth level of a sitting person, although higher partitions will bring better results. If possible, it is also worth installing ceiling panels of high sound absorption qualities to prevent sounds reflection from the ceiling and reduce the level of noise.
Recommended product: Wall
The solution is to create smaller areas by means of sound absorbing panels (Blocks, Duo) suspended on the ceiling or providing free-standing insulating and absorbing panels (Wall, Cone) – as the sound strikes more obstacles, it will not spread far. It is worth installing sound absorbing desk panels (Duo) in the work stations, as well as using the available wall surfaces for sound absorbing panels (Blocks, Canvas, Print). To ensure privacy of phone calls and facilitate focused work, it is worth providing the open space with free-standing booths of high insulation qualities (Space S).
Recommended products: Blocks, Canvas, Print, Wall, Cone, Space S, Space M, Space L
The best solution is to create a calm place for employees, which at the same time will provide a comfortable work environment. A good alternative to conference rooms are mobile, free-standing acoustic pods. They will not only provide appropriate acoustic environment for their users, but also divide large open spaces into smaller, more convenient areas. It is important to choose products of good insulation parameters (blocking the outside noise and making work more effective), high sound absorption qualities inside, proper ventilation (to allow for a long, comfortable use), as well as ergonomic facilities inside the pod (access to socket, accurate lighting or height adjustable desk).
Recommended products: Space M
According to our observations, in many companies employees run short meetings very often. In order to avoid building huge conference rooms, which usually are too spacious for short 1:1 meetings, it is worth using ready solutions for such a purpose. Acoustic pods, which sizes and amenities may be chosen according to their functions, may be a good solution in this case. A pod for two people equipped with stools and a comfortable counter will provide comfortable conditions for informal meetings.
Recommended products: Space M
Sometimes the rented office does not have a properly separated space for meetings and the administrator does not allow changes. In this situation, a good alternative to bricked up walls is to place free-standing acoustic pods. Apart from the acoustic properties, the pods divide the space and provide a friendly environment for conversations. In case of such products, great attention should be paid to the appropriate insulation parameters (blocking the outside noise and meetings can take place in favorable conditions), good sound absorption inside, proper ventilation (so that long stay in it is comfortable), as well as ergonomic solutions (access to power sockets, adequate lighting, or a comfortable seat for several people).
Recommended products: Space L
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