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Enkele relevante artikelen

 
 

 

In de loop der jaren is over het lopende onderzoek uiteraard ook gepubliceerd in de vakpers en gepresenteerd op congressen. In de teksten op deze site wordt daar af en toe naar verwezen. Vanuit de desbetreffende plek kan dan eventueel worden doorgelinkt; dezelfde artikelen staan hier in volgorde genoemd. Het is geen uitputtende lijst.

Er zijn nogal wat publicaties waarvan Konca Şaher de eerste auteur is. Die zijn hier nog niet opgenomen. Er wordt eerst gewacht op Konca's promotie.

 

Architectural Guidelines for Living Rooms, Classrooms, Offices, Sports Facilities and Restaurants

Monika Rychtáriková,Lau Nijs, Konca Şaher, Marinus van der Voorden

2004

Praag, Internoise 2004

In general technical standards to establish the acoustical quality of a room are given in terms of the reverberation time. However, depending on room shape and dimensions (from 80 to 40,000 m3), architectural function and acoustical use (single source versus multi-source), other acous-tical numbers may be more adequate. In practice there is a variety of rooms and functions on one side and a set of available acoustical quality numbers (RT, SPL, G strength, absorption coefficient, C50, U50, STI, S/N, NR-values, etc.) on the other. They may be considered as the rows and columns of a (huge) table. It is the ultimate goal of our research to fill some of the cells in this table.

Since ray-tracing programs are not very accurate in predicting RT, the results are presented in a “G-RT-diagram”, which has proven to be a powerful tool for comparison between measurements and cal-culations. In most cases the correlation found for G is higher than for RT. This is as expected, since ray-tracing models are based on sound energy propagation.

Preliminary architectural guidelines are given in mean absorption coefficients. They are more accurate than the reverberation time and are much easier to use by architects.

 

 

The development of architectural guidelines for the acoustical quality in rooms for mentally challenged people

L. Nijs, D. van Berlo, D. de Vries

2001

Rome, 17th International Congress on Acoustics

A research project is going on to improve the acoustical quality in living rooms and work spaces for mentally challenged people. Measurements have been done in four living spaces and two work places. From these measure­ments improvements will be pro­posed, where after new measurements will be carried out. Results are compared with the output from a ray-tracing computer model and with calculations based on simple rules for diffuse rooms. Differences in the order of 0-3 dB have been found for measurements versus ray-tracing, while deviations with the simple method vary from 0-5 dB.

The aim of the total research project is to improve existing situa­tions, but also to develop guidelines for architects and acoustical engineers for future plans. In this respect U50 is a useful variable to calculate the necessary amount of absorbing material in a room whit more than one speaking person. It is superior to the reverberation time and easier to use than STI.

 

 

Het gebruik van de nagalmtijd bij de normstelling van sportzalen

Lau Nijs & Aart Schuur

2004

Bouwfysica, jaargang 15, nr. 1, mei 2004, pp. 11-17

De nagalmtijd is afhankelijk van de grootte van de ruimte. Indien de nagalmtijd wordt gebruikt voor normstelling moet daar dan ook rekening mee worden gehouden. Een gymzaal vereist bijvoorbeeld een veel kortere nagalmtijd dan een sportzaal waarin een atletiekbaan is aangelegd.

 

 

Effect of room absorption on human vocal output in multitalker situations

Lau Nijs, Konca Saher and Daniël den Ouden

2008

Journal Acoustical Society of America, 123, 2, February 2008

People increase their vocal output in noisy environments. This is known as the Lombard effect. The aim of the present study was to measure the effect as a function of the absorption coefficient. The noise source was generated by using other talkers in the room. A-weighted sound levels were measured in a 108 m3 test room. The number of talkers varied from one to four and the absorption coefficients from 0.12 to 0.64. A model was introduced based on the logarithmic sum of the level found in an anechoic room plus the increasing portion of noise levels up to 80 dB. Results show that the model fits the measurements when a maximum slope of 0.5 dB per 1.0 dB increase in background level is used. Hence Lombard slopes vary from 0.2 dB/dB at 50 dB background level to 0.5 dB/dB at 80 dB. In addition, both measurements and the model predict a decrease of 5.5 dB per doubling of absorbing area in a room when the number of talkers is constant. Sound pressure levels increase for a doubling of talkers from 3 dB for low densities to 6 dB for dense crowds. Finally, there was correspondence between the model estimation and previous measurements reported in the literature.

 

 

The distribution of absorption materials in a rectangular room

Lau Nijs

2005

Rio de Janeiro, Internoise 2005 Congress

Students in Architecture are taught Sabine’s formula for the reverberation time (RT) and common theory for the sound pressure level (SPL), but actually, these equations are for a cubic space with a diffuse sound field and absorption materials distributed homogeneously through the room. The influence of room shape and uneven absorption distribution on RT has been investigated for many decades. The consequences for SPL have been dealt with much less. A simple mirror sources model is used to derive general rules for a rectangular enclosure. The model predicts RT and SPL to increase in almost any case. RT is mainly influenced by the longest room dimension, while SPL is decreased when absorption is perpendicular to the shortest dimension. It explains why ceiling absorption is effective. Some simple adaptations can be made to the common theory to estimate the effect.

 

 

The young architect's guide to room acoustics

L. Nijs & D. de Vries

2005

Acoustical Science and Technolgy, 26, 2, pp. 229-232, 2005.

Most students in architecture are unable to design a concert hall from the acoustic textbooks, espe­cially if the hall’s volume is much less than used for symphony orchestras. Therefore a method is pro­posed to read the rever­beration time and loudness from a simple G-RT-diagram as a function of vol­ume and mean absorption coeffi­cient. An “ideal curve” is proposed as  “target values” in the first stages of the design process. They are also used to in­terpret the numbers generated by computer models in or­der to readjust the shape of the hall and the materials used.

 

 

Het optimaliseren van de ruimteakoestiek voor de les- en oefenruimtes van het Conservatorium van Amsterdam

Marten Valk, Lau Nijs, Peter Heringa

2006

NAG-journaal, nr 178, maart 2006.

Different groups of musical instruments have different demands on the room acoustics of lesson and study rooms of conservatories. To apply this differentiation for the desired acoustics of the different groups of instruments, research is done with musicians in two test rooms with different volumes of about 100 and 25 m3 The acoustical parameters coulsd be changed by varying the amount of absorption panels in the test rooms. In this way, investigations are made on the desired acoustics of the different groups of instruments.The subjective experiences of the musicians are linked to the results of the objective measurements to formulate a model for the desired acoustics. The demands on the room acoustical facilities of the different groups of instruments appear to diverge a lot. Models are formulated for players of jazz wind, brass, wood wind, flutes, stringed instruments, piano, organ, strings, electrical amplified instruments, double bass jazz, vocals, non melodic percussion, mallets, kettledrums, brass ensemble, jazz group / rock band, classical ensemble, theory general and solfege. In contrast with existing models for the desired acoustics of music halls log RT = a log V + b, as formulated by Cremer and Müller and Nijs and de Vries, the loudness has an important influence on the desired acoustics of smaller rooms with volumes below 400 m3. So, there is proposed a different basic model for the relation between the room’s volume and its reverberation time: RT = p log V + q. The global values for p and q are 0.45 and 0.36 respectively.

 

 

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