Ecophon Acoustic Bulletin

The acoustic treatment of the Henriksberg pub and restaurant won a prize for best practice at European Noise at Work Summit, 12 December 2005. Watch the video of the presentation.

View the Ecophon solution for the project (NB: different conditions might require adjustments of the solution. We recommend to involve an acoustics consultant)

The project was conducted by the National Insitute for Working Life and the Ammot Association (Artisits and musicians against tinnitus) in co-operation with Gothenburg's Environment and Health Administration, the Arranger's Association, the Swedish Musicians' Union, acoustics consultancy firm Artifon and Ecophon.
Research findings are presented in "Reducing noise exposure in small music clubs"

Read more about the project at Henriksberg Restaurant in Gothenburg, Sweden (pdf)

Posted by Pierre Chigot at 12:09 PM | Permalink

NF S31- 080, Acoustics - Offices and associated areas - Acoustic performance levels and criteria by type of area, published January 2006, is the first French standard on office acoustics. It is designed as a reference document for clients to express their requirements, as well as a guide-line for office designers.

Description
Nine room types have been defined (personal office, open plan office, meeting room, etc). For each of the rooms, the standard defines three levels of performance: Standard, Efficient and Highly efficient level. For each of the level, a description of the expectable sound environment is made. Finally, a table displays the numerical values to be achieved in order to meet the targeted performance in normal conditions.

NF S31- 080 can be used in specifications like:
"(...) open spaces will be designed according to NF S 31-080, Efficient level, implying a rate of spatial decay of at least 3 dB(A) per doubling of distance, a Total noise level of 45 dB(A)Insulation from internal airborne noise of 35 dB"

The standard is issued by the Technical Committee S 30D from AFNOR (French Standardisation Member Body) including acousticians (Peutz, Gamba, etc), clients and end-user organisations (Renault, EDF, etc), quality assessment/risk management (SOCOTEC, APAVE) and representatives from the industry (AMF, Armstrong, Ecophon, Eurocoustics, etc)

Access NF S31- 080 (French and English version available)

Posted by Pierre Chigot at 10:02 PM | Permalink

Ecophon interacts daily with acoustic consultants throughout the world. To further enhance this collaboration Ecophon will arrange a 5th International Acousticians' Seminar in Helsingborg in Sweden at the end of September 2006. The theme of the seminar will be “Innovations in room acoustics”.

The seminar is to share knowledge and experience of room acoustics, ranging from the effects on people to guidelines and room acoustic design solutions.

Ecophon is proud to present an extensive two-day seminar program, including highly respected international acousticians as lecturers. Among them, we count: STI-creator Herman Steeneken, John Bradley renowned researcher on office- and classroom acoustics and Mikael Vorlander, initiative taker of standardisation on measurement of sound diffusion and scattering.

Contact

Posted by Pierre Chigot at 4:39 PM | Permalink

World Health Organization - Guidelines for Community Noise is a systematic review of scientific evidence regarding noise, annoyance, speech and hearing impairment. The document provides also relevant guideline values.

Extract 1 Interference with communication Speech (3.3)
"Longer reverberation times, especially when combined with high background interfering noise, make speech perception more difficult. Even in a quiet environment, a reverberation time below 0.6 s is desirable for adequate speech intelligibility by vulnerable groups. For example, for older hearing-handicapped persons, the optimal reverberation time for speech intelligibility is 0.3–0.5 s (Plomp 1986)"

Extract 2 Schools and preschools (4.3.2)"For schools, the critical effects of noise are on speech interference, disturbance of information
extraction (e.g. comprehension and reading acquisition), message communication and annoyance. To be able to hear and understand spoken messages in classrooms, the background sound pressure level should not exceed 35 dB LAeq during teaching sessions. For hearing impaired children, an even lower sound pressure level may be needed. The reverberation time in the classroom should be about 0.6 s, and preferably lower for hearing-impaired children. For assembly halls and cafeterias in school buildings, the reverberation time should be less than 1 s"

Extract 3 (Noise) Interference with communication (4.2.1)
"Speech signal perception is of paramount importance, for example, in classrooms or conference rooms. To ensure any speech communication, the signal-to-noise relationship should exceed zero dB. But when listening to complicated messages (at school, listening to foreign languages, telephone conversation) the signal-to noise ratio should be at least 15 dB. With a voice level of 50 dBA (at 1 m distance this corresponds on average to a casual voice level in both women and men), the background level should not exceed 35 dBA"

Posted by Pierre Chigot at 3:29 PM | Permalink

International Standard ISO/TR 3352:1974 "Acoustics - Assessment of noise with respect to its effect on the intelligibility of speech" provides methods for measurement and assessment of noise with respect to intelligibility.

Example
For a speech interference level of 35 dB, the maximum distance at which raised voice is considered to be satisfactorily intelligible is 15 m, while it would be 8,4 m for a speech interference level of 40 dB.

Comment
This indicates that from a strict Signal to Noise ratio point of view, teacher's voice in classrooms will easily reach the furthest pupil position, generally located 8 m from the blackboard.

Posted by Pierre Chigot at 9:54 AM | Permalink

- Speech privacy in open plan office asks for reduced sound propagation between workstations.
Link to it! Spread it! Enjoy it.

More about open plan acoustics.

Previous post on speech privacy

Posted by Pierre Chigot at 10:02 PM | Permalink

Unwanted sound (noise) has been documented to be a serious problem for hospitalised patients. In some cases, most often different forms of intensive care noise levels can reach levels that are above what is advisable from an health and safety perspective (work environment perspective). In many hospitals noise levels are not a threat to healthy people and is the vicinity of what we would find acceptable for an office (for ex 50 dB (A)).

Is noise considered a problem in today’s hospitals? The answer probably lays in the fact that being ill and having to be hospitalised means that the patient has lost the sense of control in relation to the surrounding environment. Any type of stressor can have a negative impact. Loosing out on sleep has shown to be one such stressor to patients.

Background
The sleep study by Dr Sören Berg, University Hospital of Lund investigated what effects an improved room acoustics had on objective sleep quality. Even though no such research has been performed before, the hypothesis was that improved room acoustics would lead to lesser fragmentation of sleep when subjects were sleeping under noisy conditions. Objective sleep quality was assessed by EEG. Through this information it is possible to derive the quality of sleep as well as the distribution of the sleep stages (1-4 and REM).

Design
12 young students (20-25 years) acted as subjects in the study. The slept three nights in an unused department in an small hospital in the south of Sweden. During all the night the were subjected to 12 environmental sounds in the range of 27-58 dB (A). The first night was used to get the subjects used to the electrodes, the bed etc, and no EEG data was recorded.

Results
The second night the room was equipped with a sound reflective ceiling (gypsum board with Akutex T paint) that was impossible to distinguish from standards Ecophon ceilings. The subjects were unaware about the modifications to the environment.

The third night the room was equipped with a sound absorbing ceiling and all the other procedures were repeated. In the room used for the study the use of a sound absorbing ceiling did not affect the noise level in the room. The average improvement in the reverberation time was 0,12 seconds giving the room a reverberation time of approximately 0,4 seconds.

What did the study show?
In the situation with short reverberation time (sound absorbing ceiling) sleep was less disturbed by the 12 environmental sounds. This means that sleep was less fragmented, i.e. caused less EEG defined awakenings.

The findings suggests that a room with a short reverberation makes it possible to ”shield of” sound during sleep. When sound appears in a room like this it might be perceived ass less threatening and our brain sees no point in waking the person up or increasing the level of activation for the individual.

Reference
Impact of reduced reverberation time on sound-induced arousals during sleep, Sleep, 2001 May 1, 24(3):289-92.

Access article

Posted by at 4:53 PM | Permalink

Privacy and confidentiality are given more and more importance in Europe, USA and other countries around the world. 2006 has been chosen to celebrate the 50th anniversary of speech privacy, a discipline pioneered by Leo Beranek and colleagues beginning in 1955.

On 7th June, during the 151st ASA meeting (Providence, RI), special speech privacy events are being organized by ANSI S12 WG44, the joint North American standardisation subcommittee on speech privacy in healthcare facilities.

Program (download program below)
- fourteen invited and contributed papers
- third international meeting of the Joint Subcommittee
- celebration dinner in honor of the pioneers of speech privacy research and practice.

More information about the Providence meeting

50_YEARS_PRIVACY_PROGRAM

Posted by Pierre Chigot at 2:38 PM | Permalink

German Standard DIN 18041 "Acoustical quality in small to medium-sized rooms" includes a table called “Guideline values for the free ceiling and wall surface areas to be covered with sound absorbers as a multiple of the room basic area (…)”. The table Download file presents for different room types the amount of sound absorbers to be used depending on their sound absorption performance (expressed as αw).

I asked two questions to Bernd Kunzmann, Chairman of the DIN Technical Committee responsible for the writing of DIN 18041.

The answers confirm that reduction of sound pressure level is at least as important as reverberation time as a room acoustic descriptor.

Question 1
What were the assumptions made regarding the recommended reverberation time in the mentioned rooms?

Answer
Since they represent rather different situations (size, furnishing, etc), one could assume that each room type has an optimal reverberation time. This optimal reverberation time can then be reached if the recommended amount of absorption is used.

Question 2
Was the amount then calculated from EN 12354-6:2003 "Building acoustics - Estimation of acoustic performance of buildings from the performance of elements. Sound absorption in enclosed spaces"?

Answer
Your question concerns from our point of view exclusively rooms relevant for speech communication at short distances (rooms of category B). The specification of measures taking mostly reverberation time into account would be inadequate. The main goal is the increase of the sound absorption, needed for the reduction of the background noise level and for the reduction of the reverberation time. No assumptions have been made regarding values of reverberation time.

The reverberation time seems to be of secondary importance for the field of application. Main objective is the insertion of the required equivalent sound absorption area. Corresponding knowledge has been gathered based on measurements and calculations (approx. 3 dB). EN 12354-6 specifies a calculation model for determining the entire equivalent sound absorption area for the determination of the reverberation time. The calculation procedure is applicable to rooms of category A in sense of DIN 18041.

Purchase DIN 18041 (in German only)

Posted by Pierre Chigot at 3:18 PM | Permalink