Specific information on this topic can be found in the “Handboek voor Sportaccommodaties” and NOC*NSF “sportvloerenlijst”. At national level the work of Kiwa. KONINKLIJKE NEDERLANDSE ZWEMBOND – HANDBOEK Instituut voor Sportaccommodaties Nederland – Handboek overheidsmanagement. Brugge: Vanden Broele. . Sportaccommodaties in. Nederland. Utrecht: Mulier. Instituut. Retrieved from.
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Auralization examples to discuss the reverberation time as a standard for sports facilities. This page is made to make sounds audible.
The main part of the text is copied here. However it is somewhat extended to incorporate more sound samples than dealt with in the original paper. The present website is just one “stand-alone” page. However, it is also embedded in a more extended website, written for students in Architecture. Unfortunately for foreign visitors, this website is in Dutch, but yet.
Wees welkom op de site: In the Netherlands and Belgium the standards for sports facilities are given as maximum values for the reverberation time. Since the dimensions of sports facilities may vary considerably from tom 3 and the reverberation time depends on the volume, they are given as increasing values with increasing dimensions. In the design stage of a hall, calculations are made by summing the absorptive surfaces. In many cases Sabine’s equation zportaccommodaties used sportaccommodaites calculate the reverberation time, but sports halls have usually non-cubic dimensions and absorbing materials are always inhomogeneously distributed, since the floor is non-absorbing and the ceiling is preferred for absorption.
Hence the reverberation time may increase considerably compared to Sabine’s. The international standard ISO  provides a method to calculate this effect. If the reverberation time appears too long, it seems as if the effect of the absorption is lower than calculated in the design stage. However, adding absorption is not necessarily a solution; the distribution through the hall sportxccommodaties be more important. In this paper three aspects will be discussed: Some architectural solutions will be given to overcome long reverberation times.
It appears very instructive to listen to sound samples from auralizations in a virtual hall, so during the actual congress presentation some samples are presented. In the present website similar sounds are given. In a sports hall the sound pressure level plays an important role.
The NAG-DAGA congress, March 2009 in Rotterdam and these web pages
The sound may come from a “wanted source” speech for instance or from other “noise sources” in the hall:. The value L W represents the acoustic sound power level of the source. The source-receiver distance is given by rwhile Q stands for the directivity of the source. There are numerous books that give more details. Our own work is described in more detail in . This contradicts experience, so Barron  developed an alternative, which in our case  is written as: In the design stage, A is calculated from the absorption coefficients of all materials.
If the hall is finished, measuring the contributions of all surfaces separately is almost impossible and the total value A is measured instead from the reverberation time. In many cases Sabine’s formula is used:.
Kiwa ISA Sport laboratory
Another characteristic determining the acoustical quality is the occurrence of “flutter echoes”. In very reverberant halls they cannot be heard, but if all absorption is put on the ceiling echoes may be found along the length and width dimensions of the hall.
They can be heard in practice and can be seen in plots of decay curves, but at present there is no method to quantify them. The phrase “flutter echoes should not be heard”, spogtaccommodaties used in older standards is too informal for legal standards. The floor plan is given in figure 1.
The program produces many acoustical variables, but our focus is on the reverberation time -5 to dB and the sound pressure level. Energy sportaccommmodaties responses from the program are used to study the echoes in the hall.
Auralizations are made by convolution of the impulse responses from the program and “dry” sound samples. A wanted source is at position A. It is represented by speech originally recorded in the anechoic rooms in Delft and Leuven. Noise signals are generated at position B. These signals are represented by four talkers or by impulsive sounds from a basketball dribble. Microphone positions are as indicated; one position number 14 is at the mean free path distance mfp from the source, which is The source height is 1.
These effects have been measured in real halls, but are also found in computer models. A sports facility used for ray-tracing simulations plus auralizations. The main source is at position A.
If noise is added it is generated at position B. For microphone sporyaccommodaties 14, the source-receiver distance equals The first computer runs were made to show the effect of the amount of absorption plus the distribution along the surfaces. Situation d is more a hypothetical case. This leads to the minimum reverberation that is possible . The left hand figure 2 gives the response to an energy pulse as calculated in the ray tracing model for microphone The right hand figure 2 shows the schroeder curves as derived from the left hand curve by backward integration.
These are the spoetaccommodaties that should be used to derive the reverberation times by curve fitting along the four slopes. The differences are immense; RT -values are 6. A complicating factor is that curves handboe and d are straight lines, but curves b and c are concave.
In case a this level is This is a remarkable result. If A is calculated from the RT-values reversing Eq. The reason is that RT is found from the curves after 0. As can be seen in the left hand figure there are only minor differences for cases bc and d before 0. Figure 3 gives the same results of SPL and RT for the four situations a to dbut now combined in one SPL-RT- graph, which is very instructive to compare measured and calculated microphone positions in a room.
The four microphone positions 1, 2, 3 and 18 from figure 1 are added to microphone position The value of RT is found as one value for all receiver positions RT is 6. Echograms left and schroeder curves bottom as calculated from the four cases as given in the text. Microphone position is number Reference sound level is taken as 60 dB at 1 m in an anechoic chamber. SPL and RT for the four cases explained in the text, hndboek the five microphone numbers indicated in figure 1.
Position 14 is given as full dot, the other four as open sportaccommodzties. The reference level is 60 dB at 1 m in the anechoic chamber. Levels at microphone position 1 are slightly higher due to the hall’s reflections.
This is not the case in the ray-tracing results. This is where Sabine’s theory is most reliable, since reverberant situations lead to diffuse fields. All four curves a to d show a slight increase of SPL at the mfp distance. This is due to the non-cubic space as explained in . The reverberation times of curves bc and d appear to depend strongly on the distribution of absorbing materials.
In sportaccommodaries special case d the reverberation time is even below the one predicted by equation 3. Actually ray-tracing theory predict a minimum value equal to Eyring’s reverberation time instead of Sabine’s. Eyring’s value is always lower. RT values at position 14 hndboek The results from the sportcacommodaties The trend is the same but the mutual differences from the standard are less. It is difficult to say which value should be preferred; we are planning scale model measurements to investigate the effect.
However, situation d should tend to Eyring’s value, but the minimum value from standard is Sabine’s. That is not very likely. Results from another ray-tracing program Odeon confirm the Catt-results. Differences are greater at position So SPL depends only marginally on the spportaccommodaties of absorbing materials. In fact this last result means that the reverberation time is not a good predictor if we want to characterize the sound pressure level in a sports facility.
Measuring SPL directly gives better information. This is not very difficult in practice under one condition: Simple methods with exploding balloons etc. The echograms of the left hand part of figure 2, show strong differences in echo behavior.
Sound samples have been made, with the aid of the auralization techniques of the ray-tracing program, to investigate the effect in more detail. Calibrating the loudness of the headphone signal. The sound samples can be best listened with ear phones, but the demonstrations can only be put into perspective when sportacommodaties loudness is calibrated properly. In our laboratory we did that for one type Beyer headphone.
The loudness is different for other types and brands.