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.
Het proefschrift van Konca Şaher
Er zijn enkele publicaties waarvan Konca Şaher de eerste auteur is. Die zijn hier niet opgenomen. Wel is een link gegeven naar het proefschrift dat uiteraard wel verwijzingen bevat naar de artikelen.
De link verwijst naar de "schatkamer" van de TUDelft. Vanaf die plaats is ook een pdf te downloaden.
Acoustical Design Guidelines for Living Rooms for Adults with intellectual Disabilities
Promotiedatum: 5 juni 2013
The aim of this thesis is to investigate the effects of building design tools on acoustical quality parameters in living rooms for adults with intellectual disabilities (ID) and develop acoustical design guidelines for architects. This study is specifically concerned with the validation of auralizations as an assessment tool and establishing the relation between user satisfaction and absorption amount by listening tests prepared from auralizations. This project was motivated because of lack of data available to architects on the need of adults with ID. Poor acoustic conditions were shown to be one of the key barriers during audiological intervention for adults with ID among who prevalence of hearing impairment is 30%. Complaints regarding poor acoustics by staff members in institutions were also recorded. The impact of building design tools (volume, absorption amount, furniture, location of absorption and room shape) on acoustical parameters was investigated. Based on the results of measurements and computer simulations, absorption amount was proposed as the most important quality indicator. For the validation of auralizations, comparisons between binaural in-situ recordings and auralizations were drawn. The results showed that although the auralizations and binaural in-situ recordings evoked different sensations, it was possible to re-create the acoustical environment with a level between rather different and slightly different to the real environment. Auralizations were shown to be a strong assessment tool to investigate the relative differences between different architectural designs. Following the validation of auralizations, subjective assessment of absorption amount, location of absorption, furniture, absorptive ceiling, screens and noise type was investigated by listening tests among both ''normal-hearing people'' and ''hearingimpaired people". Results confirmed that absorption amount is the most important quality indicator. It was shown that the mean absorption coefficient (alpha mean) of at least 0.28 in mono-noise and 0.40 in two-noise condition is necessary to achieve a user satisfaction above the level of "good" for "normal-hearing people". The results of "hearing-impairedpeople" consistently showed at least one subjective degree decrease compared with "normal-hearing people". Based on the findings of listening tests, a quality rating system as a function of mean absorption coefficient (alpha mean) is developed. In conclusion, this thesis offers design guidelines for architects and makes contribution to improve acoustical quality in living rooms for adults with ID. These guidelines include the "Room Quality Prediction Spreadsheet" in reference to the developed quality rating system, absorption application categories and suitable generic absorption materials for each category.
Monika Rychtáriková,Lau Nijs, Konca Şaher, Marinus van der Voorden
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.
L. Nijs, A. Schuur
Leuven, Research in Building Physics
The reverberation time is used in legal demands to provide for good acoustical quality in a sports hall. However, the reverberation time depends too much on the hall’s vol-ume, so the volume should be taken into account as well. There is a second drawback to the reverberation time: calculated and measured de¬cay curves may be rather concave, especially in shoe box shapes and it is very hard to estimate the noise lev¬els in a sports hall from the reverberation time. An alternative is possible by simple measurement of the strength of the diffuse sound field, but this method requires an extra indication about the characteristics of the loudspeaker used for the measurements
L. Nijs, D. van Berlo, D. de Vries
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.
Lau Nijs, Pernette Versteeg, Marinus van der Voorden
Kyoto. 18th International Congress on Acoustics
Common equations for sound level predictions in diffuse rooms are too pessimistic about the possibilities for noise reduction when adding absorption. Barron’s equation appears more appropriate in “shoe boxes”, but ray tracing models predict even more decrease when L- and U- shaped rooms are used, since the corners within these rooms cause an extra reduction. However, room shape as a building design parameter is only effective in combination with relatively high absorption coefficients.
Lau Nijs, Konca Saher and Daniël den Ouden
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.
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.
L. Nijs & D. de Vries
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.
Marten Valk, Lau Nijs, Peter Heringa
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.
L. Nijs, M. Rychtáriková
In sports facilities the height of the hall is mainly small when compared to the length of the hall. This non-cubic form is the first reason why deviations are found between the reverberation time from Sabine's method on one side and measurements, ray-tracing predictions and calculations from standard IEC-12354-6 on the other. A second reason why reverberation times increase even more is that normally most absorption is positioned on the ceiling. Hence, to meet legal standards expressed in reverberation times, it seems that more absorption is needed than predicted by Sabine's method. However, sound pressure levels are much less sensitive to the distribution of materials, which will be illustrated by examples from computer calculations and auralizations. Some differences between sound samples may be heard, but they vanish in noisy situations. In this paper the question will be discussed if there is a better acoustic variable than the reverberation time to express and measure the acoustical quality in a sports facility.
Artikelen in "Bouwfysica", het kwartaalblad van de "Nederlands Vlaamse
Het gebruik van de nagalmtijd bij de normstelling van sportzalen
Lau Nijs & Aart Schuur
Bouwfysica, jaargang 15, nr. 1, 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.
Akoestische kwaliteit in klaslokalen in België en Nederland
L. Nijs & G. Vermeir
Bouwfysica, jaargang 15, nr. 4, 2004,  pp. 13-22
Het optimaliseren van de ruimteakoestiek voor de les- en oefenruimtes van het Conservatorium van Amsterdam
M. Valk, P.H. Heringa, L. Nijs
Bouwfysica, jaargang 17, nr. 3, 2006, pp. 11-15
Akoestiek in sportzalen
Een te lange nagalmtijd in een sportzaal kan worden veroorzaakt door een gebrek aan absorptie of door flutterecho's, die meestal ontstaan tussen de wanden als alle absorptiematerialen op het plafond en aan de bovenzijde van de wanden zijn geconcentreerd. Als bij meting de geluidsterkte G en de early decay time EDT te hoog zijn, is de hoeveelheid absorptie te laag. Indien EDT en G wel in orde zijn, is de verdeling van de absorptie over de ruimte problematisch. Absorberende en/of verstrooiende materialen in de onderste meters van de wanden bieden dan soelaas om flutterecho's te bestrijden, waarbij nog onbekend is in hoeverre hoorbare flutters ook hinderlijk zijn en bestrijding noodzakelijk is. De spreiding in EDT en G is overigens wel te groot om daaruit een alternatieve kwaliteitsmaat af te leiden.
Op dit artikel wordt commentaar geleverd door Evert de Ruiter;
en daarop komt weer een weerwoord:
Geluidbeheersing in sportzalen
Evert de Ruiter en Marc Noordermeer
Geluidbeheersing in sportzalen Een antwoord aan Evert de Ruiter en Marc Noordermeer